John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

John Joannopoulos, an innovator and mentor in the fields of theoretical condensed matter physics and nanophotonics, has been named the recipient of the 2024-2025 James R. Killian Jr. Faculty Achievement Award.

Joannopoulos is the Francis Wright Davis Professor of Physics and director of MIT’s Institute for Soldier Nanotechnologies. He has been a member of the MIT faculty for 50 years.

“Professor Joannopoulos’s profound and lasting impact on the field of theoretical condensed matter physics finds its roots in his pioneering work in harnessing ab initio physics to elucidate the behavior of materials at the atomic level,” states the award citation, which was announced at today’s faculty meeting by Roger White, chair of the Killian Award Selection Committee and professor of philosophy at MIT. “His seminal research in the development of photonic crystals has revolutionized understanding of light-matter interactions, laying the groundwork for transformative advancements in diverse fields ranging from telecommunications to biomedical engineering.”

The award also honors Joannopoulos’ service as a “legendary mentor to generations of students, inspiring them to achieve excellence in science while at the same time facilitating the practical benefit to society through entrepreneurship.”

The Killian Award was established in 1971 to recognize outstanding professional contributions by MIT faculty members. It is the highest honor that the faculty can give to one of its members.

“I have to tell you, it was a complete and utter surprise,” Joannopoulos told MIT News shortly after he received word of the award. “I didn’t expect it at all, and was extremely flattered, honored, and moved by it, frankly.”

Joannopoulous has spent his entire professional career at MIT. He came to the Institute in 1974, directly after receiving his PhD in physics at the University of California at Berkeley, where he also earned his bachelor’s degree. Starting out as an assistant professor in MIT’s Department of Physics, he quickly set up a research program focused on theoretical condensed matter physics.

Over the first half of his MIT career, Joannopoulos worked to elucidate the fundamental nature of the electronic, vibrational, and optical structure of crystalline and amorphous bulk solids, their surfaces, interfaces, and defects. He and his students developed numerous theoretical methods to enable tractable and accurate calculations of these complex systems.

In the 1990s, his work with microscopic material systems expanded to a new class of materials, called photonic crystals — materials that could be engineered at the micro- and nanoscale to manipulate light in ways that impart surprising and exotic optical qualities to the material as a whole.

“I saw that you could create photonic crystals with defects that can affect the properties of photons, in much the same way that defects in a semiconductor affect the properties of electrons,” Joannopoulos says. “So I started working in this area to try and explore what anomalous light phenomena can we discover using this approach?”

Among his various breakthroughs in the field was the realization of a “perfect dielectric mirror” — a multilayered optical device that reflects light from all angles as normal metallic mirrors do, and that can also be tuned to reflect and trap light at specific frequencies. He and his colleagues saw potential for the mirror to be made into a hollow fiber that could serve as a highly effective optical conduit, for use in a wide range of applications. To further advance the technology, he and his colleagues launched a startup, which has since developed the technology into a flexible, fiber-optic “surgical scalpel.”

Throughout his career, Joannopoulos has helped to launch numerous startups and photonics-based technologies.

“His ability to bridge the gap between academia and industry has not only advanced scientific knowledge but also led to the creation of dozens of new companies, thousands of jobs, and groundbreaking products that continue to benefit society to this day,” the award citation states.

In 2006, Joannopoulos accepted the position as director of MIT’s Institute for Soldier Nanotechnologies (ISN), a collaboration between MIT researchers, industry partners, and military defense experts, who seek innovations to protect and enhance soldiers’ survivability in the field. In his role as ISN head, Joannopoulos has worked across MIT, making connections and supporting new projects with researchers specializing in fields far from his own.

“I get a chance to explore and learn fascinating new things,” says Joannopoulos, who is currently overseeing projects related to hyperspectral imaging, smart and responsive fabrics, and nanodrug delivery. “I love that aspect of really getting to understand what people in other fields are doing. And they’re doing great work across many, many different fields.”

Throughout his career at MIT, Joannopoulos has been especially inspired and motivated by his students, many of whom have gone on to found companies, lead top academic and research institutions, and make significant contributions to their respective fields, including one student who was awarded the Nobel Prize in Physics in 1998.

“One’s proudest moments are the successes of one’s students, and in that regard, I’ve been extremely lucky to have had truly exceptional students over the years,” Joannopolous says.

His many contributions to academia and industry have earned Joannopoulos numerous honors and awards, including his election to both the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a fellow of both the American Physical Society and the American Association for the Advancement of Science.

“The Selection Committee is delighted to have this opportunity to honor Professor John Joannopoulos: a visionary scientist, a beloved mentor, a great believer in the goodness of people, and a leader whose contributions to MIT and the broader scientific community are immeasurable,” the award citation concludes.

© Photo: Jose-Luis Olivares, MIT

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers

An intricate, honeycomb-like structure of struts and beams could withstand a supersonic impact better than a solid slab of the same material. What’s more, the specific structure matters, with some being more resilient to impacts than others.

That’s what MIT engineers are finding in experiments with microscopic metamaterials — materials that are intentionally printed, assembled, or otherwise engineered with microscopic architectures that give the overall material exceptional properties.

In a study appearing today in the Proceedings of the National Academy of Sciences, the engineers report on a new way to quickly test an array of metamaterial architectures and their resilience to supersonic impacts.

In their experiments, the team suspended tiny printed metamaterial lattices between microscopic support structures, then fired even tinier particles at the materials, at supersonic speeds. With high-speed cameras, the team then captured images of each impact and its aftermath, with nanosecond precision.

Their work has identified a few metamaterial architectures that are more resilient to supersonic impacts compared to their entirely solid, nonarchitected counterparts. The researchers say the results they observed at the microscopic level can be extended to comparable macroscale impacts, to predict how new material structures across length scales will withstand impacts in the real world.

“What we’re learning is, the microstructure of your material matters, even with high-rate deformation,” says study author Carlos Portela, the Brit and Alex d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. “We want to identify impact-resistant structures that can be made into coatings or panels for spacecraft, vehicles, helmets, and anything that needs to be lightweight and protected.”

Other authors on the study include first author and MIT graduate student Thomas Butruille, and Joshua Crone of DEVCOM Army Research Laboratory.

Pure impact

The team’s new high-velocity experiments build off their previous work, in which the engineers tested the resilience of an ultralight, carbon-based material. That material, which was thinner than the width of a human hair, was made from tiny struts and beams of carbon, which the team printed and placed on a glass slide. They then fired microparticles toward the material, at velocities exceeding the speed of sound.  

Those supersonic experiments revealed that the microstructured material withstood the high-velocity impacts, sometimes deflecting the microparticles and other times capturing them.

“But there were many questions we couldn’t answer because we were testing the materials on a substrate, which may have affected their behavior,” Portela says.

In their new study, the researchers developed a way to test freestanding metamaterials, to observe how the materials withstand impacts purely on their own, without a backing or supporting substrate.

In their current setup, the researchers suspend a metamaterial of interest between two microscopic pillars made from the same base material. Depending on the dimensions of the metamaterial being tested, the researchers calculate how far apart the pillars must be in order to support the material at either end while allowing the material to respond to any impacts, without any influence from the pillars themselves.

“This way, we ensure that we’re measuring the material property and not the structural property,” Portela says.

Once the team settled on the pillar support design, they moved on to test a variety of metamaterial architectures. For each architecture, the researchers first printed the supporting pillars on a small silicon chip, then continued printing the metamaterial as a suspended layer between the pillars.

“We can print and test hundreds of these structures on a single chip,” Portela says.

Punctures and cracks

The team printed suspended metamaterials that resembled intricate honeycomb-like cross-sections. Each material was printed with a specific three-dimensional microscopic architecture, such as a precise scaffold of repeating octets, or more faceted polygons. Each repeated unit measured as small as a red blood cell. The resulting metamaterials were thinner than the width of a human hair.

The researchers then tested each metamaterial’s impact resilience by firing glass microparticles toward the structures, at speeds of up to 900 meters per second (more than 2,000 miles per hour) — well within the supersonic range. They caught each impact on camera and studied the resulting images, frame by frame, to see how the projectiles penetrated each material. Next, they examined the materials under a microscope and compared each impact’s physical aftermath.

“In the architected materials, we saw this morphology of small cylindrical craters after impact,” Portela says. “But in solid materials, we saw a lot of radial cracks and bigger chunks of material that were gouged out.”

Overall, the team observed that the fired particles created small punctures in the latticed metamaterials, and the materials nevertheless stayed intact. In contrast, when the same particles were fired at the same speeds into solid, nonlatticed materials of equal mass, they created large cracks that quickly spread, causing the material to crumble. The microstructured materials, therefore, were more efficient in resisting supersonic impacts as well as protecting against multiple impact events. And in particular, materials that were printed with the repeating octets appeared to be the most hardy.

“At the same velocity, we see the octet architecture is harder to fracture, meaning that the metamaterial, per unit mass, can withstand impacts up to twice as much as the bulk material,” Portela says. “This tells us that there are some architectures that can make a material tougher which can offer better impact protection.”

Going forward, the team plans to use the new rapid testing and analysis method to identify new metamaterial designs, in hopes of tagging architectures that can be scaled up to stronger and lighter protective gear, garments, coatings, and paneling.

“What I’m most excited about is showing we can do a lot of these extreme experiments on a benchtop,” Portela says. “This will significantly accelerate the rate at which we can validate new, high-performing, resilient materials.”

This work was funded, in part, by DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies (ISN), and carried out, in part, using ISN’s and MIT.nano’s facilities. 

© Image: Courtesy of the researchers