Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Symposium X_buonassisi_800 wideTonio Buonassisi, Massachusetts Institute of Technology

Finding a Path from “Promise” to “Performance”—Toward Realizing Novel Materials Predicted via Generative AI

Written by Sophia Chen

It’s all the rage: artificial intelligence—from generative models to automated laboratories—will help researchers find novel and useful materials faster. But Tonio Buonassisi, a mechanical engineer at Massachusetts Institute of Technology, knows that to get to that place, the field has its work cut out for it.

“This is not your normal tech-vangelist talk where I'm going to go up and show you how great AI is and how autonomous labs are going to rock the world,” said Buonassisi during Thursday’s Symposium X. “Yes, I do believe that. And I also believe that the path to getting there is a hard one.”

In Thursday’s Symposium X, titled “Finding a Path from ‘Promise’ to ‘Performance’—Toward Realizing Novel Materials Predicted via Generative AI,” Buonassisi outlined his perspectives on the state of automation and automated materials discovery, as well as the role of AI in these processes.

Buonassisi focused on pragmatic challenges. The adoption of AI will involve growing pains, he says. He described the trajectory as curve, where the field will hit what feels like unproductive bottlenecks: “You're putting in a lot of investment and not getting out much return. So this talk is about a lot of that part of the curve, and creating community around getting us over that part.”

Currently, the materials community has already adopted automation in a variety of settings. Scientists at the University of Liverpool, for example, use co-bots, or robots designed to work in close proximity to humans. Researchers at Boston University have also developed a robot arm that coordinates with 3D printers to manipulate materials samples.

Working at Singapore’s Agency for Science, Technology, and Research, Buonassisi started a program known as Accelerated Materials Development for Manufacturing, where they adopted a method known as “islands of automation.” To do this, instead of aiming to create a fully autonomous materials discovery process, they focused on accelerating “specific parts of the process and […] strategically targeted those points in the workflow that require more time, or that suffer from irreproducibility due to human factors,” he said.

The adoption of AI, which largely comprises models known as neural network, presents many challenges for the field, Buonassisi described in the talk. For example, the field needs to better identify which problems are most appropriate for autonomous or automated systems. On top of that, they need to increase the odds that experiments can actually synthesize and test an AI-predicted material. He listed several practical questions in the use of AI: for example, how should researchers choose a neural network architecture? How do they select, obtain, and validate training data? How should researchers represent materials to the neural network? How do they diagnose issues when things are going wrong? How should they select candidate materials that the neural network generates? How should they quantify the uniqueness or the novelty of the AI-generated materials? “These are […] examples of some of the things that, in my opinion, would yield truly high-impact papers, if you're a graduate student, postdoc, or early-stage career professor,” said Buonassisi. Using AI to discover unusual materials presents a particular challenge, he said. Experts have concluded that they would probably not have been able to predict the cuprates, high-temperature superconductors, given today’s AI tools and data prior to 1987 when researchers discovered the material.

The field should also critically examine the social structures that drive materials research, Buonassisi said. Individuals face different incentives than those of academia as an institution, and that can present a tension. While Buonassisi says this is a systemic problem and does not promise any solutions, he proposes a different academic structure in which the total number of students and postdocs are reduced. As they become more senior, they begin to manage “undergraduate researchers and staff who can augment their capabilities, who can complement some of their weaknesses in computation automation, in domain expertise,” he said.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Ying Diao, University of Illinois at Urbana-Champaign Symposium X_Diao_800 wide_2

Printing Polymer Electronics for Sustainable Earth and Habitable Mars

Written by Sophia Chen

During Ying Diao’s talk on Wednesday, she showed an image of a printer roll—not of paper, but semiconductors. “Organic electronics can be made […] akin to the way we make newspapers,” she said. These methods, which fall under the technique of 3D printing, promise cheap, high-throughput, and on-demand production. Consequently, researchers are investigating methods and materials for applications ranging from solar power to agriculture. Diao discussed the state of the technology in her talk, titled “Printing Polymer Electronics for Sustainable Earth and Habitable Mars.”

For their printed electronics, Diao’s laboratory uses conjugated polymers. While conjugated polymers are inherently semiconductors, when doped, these organic molecules can be as conductive as metals. Such organic molecules are already used in wearable electronics such as the organic light-emitting diodes in smartwatches. Researchers can modulate these materials’ conductivity over 14 orders of magnitude, she said. They have also recently used three-dimensional conjugated polymers to create structural color, where an object’s color derives from light interference with microscale or nanoscale structures. (Many animals, such as butterflies, exhibit structural color.) They also discover and design new materials using both physics-based approaches as well as artificial-intelligence-aided approaches.

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Diao believes the future generation of organic electronics materials will be semiconductors that are chiral. The structure of chiral materials exhibits either right-handedness or left-handedness, meaning they lack mirror symmetry. (A helix is an example of a chiral structure.) Chiral structures are common in nature, such as in chlorophyll. The chlorophyll’s chirality makes charge transport much more efficient during photosynthesis. Chiral organic semiconductors could offer similar advantages. In recent work, her team found that they could create helical organic semiconductors through 3D printing. The chirality emerged by adjusting the flow rate and concentration of the material during printing.

Notably, when Diao and her group analyzed the material, they found that it exhibited chirality on multiple scales—from the micron-scale to the nanometer-scale. “We have a helix within a helix within a helix,” she said. This nested helicity also occurs in collagen.

Chiral organic semiconductors would be well-suited for various next-generation electronics, said Diao. For example, when hit with light, chiral molecules sustain excitons longer than planar molecules, a quality useful for solar cells.  They could also be useful for spintronics.

Diao ended her talk discussing a prototype device using printed electronics to aid agriculture. They designed the device with futuristic missions for inhabiting Mars in mind. The device consists of a stretchable sensor for monitoring the growth rate for plants. Printed electronics are promising for extraterrestrial applications because they are lightweight and high performance, she said.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Symposium X_Duran_800 wideCarolyn R. Duran, Apple Inc.

Oh, The Things We Build! What Materials Research Looks Like at Apple

Written by Molly McDonough

How does a $2 trillion company, like Apple, develop the best materials they can for the products they make? This question is exactly what Carolyn Duran, Senior Director, Product Integrity at Apple, discussed during her talk Oh, The Things We Build! What Materials Research Looks Like at Apple. Apple’s hardware engineering team puts a significant focus on the impact of materials on product development. The team, led by Duran, works to improve the durability, recyclability, and reusability of the other two billion Apple products that are currently in use. Duran’s talk focused on three materials use cases: glass in iPhone screens, aluminum used for MacBook casings, and plastics used in keyboards.

Testing for materials durability for glass in iPhone screens focuses primarily on determining how the glass fractures, and how to reduce the likelihood of fracture. The failure analysis falls into four broad categories: mechanical, optical, scratch, and coating durability. By tuning the crystallinity of the glass through glass cooling and promoting nucleation and crystal growth through the annealing process, the microstructure of the cover glass can be modified to decrease the likelihood of fracture. Additionally, the team at Apple worked with corporate partners, like Corning, to optimize the chemical strengthening process of the glass. By using ion exchange, one can encourage compressive stress in the glass at the surface, leading to the closure of fractures. This work resulted in a four times reduction in failures in the field with ceramic glass going from iPhone 11 to iPhone 12.

Next, Duran focused on how the alloy compositions of aluminum used in MacBook laptops have changed over the years to improve durability while maintaining the look and feel Apple users know and love. Apple uses 6000 series aluminum alloys for their MacBook products, which are fabricated using an extrusion/sheet process followed by precipitation strengthening. This is followed by aluminum anodization, which is an aqueous electrochemical process that oxidizes the surface to form an amorphous Al2O3. This leaves the surface porous, alloying it to be dyed to various colors.

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The alloy team set out to find a new aluminum alloy that was more durable than the previous version by leveraging computational materials science to analyze material yield and solubility for hundreds of alloys. From the hundreds of alloys, the team picked the 10 best alloy options. From this, two alloys made it to product testing, and additional modifications were made following this testing. The new material passed Apple’s qualification process in less than six months, and led to a 30% increase in strength.

Lastly, Duran discussed how Apple improves plastics used in keyboards. Apple’s keyboard keys consist of four layers: top hard coat for protection, a color coat, a base coat for opacity, and a tinted diffuse substrate layer for glyph color and light scattering. Quality and durability issues commonly arise in keyboards, like top coat staining, glyph transmissivity, and side wall light leakage. The top coat staining issue was reduced by testing various solvent- and water-based solutions. The team found that solvent-based low volatile organic compounds showed the lowest color change due to chemical staining.

A large part of the materials development at Apple also focuses on minimizing the environmental impact of manufacturing Apple products. The company focuses primarily on reducing its impact on the climate, utilizing resources that can be recycled, and focusing on smart chemistry, meaning using chemicals that won’t end up as “forever chemicals” in the environment. For example, Apple has reduced the amount of CO2 produced from their anodization process by over 72% by utilizing ELYSIS™ technology. Apple has also transitioned to utilizing more recycled and reusable materials, including reducing the plastic in their packaging by 18% since 2015.

Apple has put a large stake into using materials science and engineering to solve real-world problems for their customers.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Keith A. Brown (Boston University), John Dunlap (UES, Inc. and Air Force Research Laboratory), Robert Epps (National Renewable Energy Laboratory), Jason Hattrick-Simpers (University of Toronto) and Kiran Vaddi (University of Washington)

How to Build A Self-Driving Lab

Written by Sophia Chen

John Dunlap's PhD research could be tedious. The chemist, now working with UES, Inc., and Air Force Research Laboratory (AFRL) contractor in Ohio, was developing polymer-coated quantum dots for biomedical applications at the University of South Carolina. The synthesis process was partially automated, but on many days, he would have to sit around and wait to press a button every 15 minutes. To test the samples, he would have to walk down three floors to use the instruments. And then he would do this over and over again, zeroing in on the recipe he sought. "It was a lot of blood, sweat, and tears on my end," he told the crowd during Thursday's Symposium X - MRS/The Kavli Foundation Frontiers of Materials.

By the time Dunlap obtained his PhD degree in 2022, materials science researchers had begun adopting new automation strategies that pushes the exhausting repetitive laboratory work to robots and computers. During the panel discussion on “How To Build A Self-Driving Lab,” Dunlap, along with Keith A. Brown of Boston University, Jason Hattrick-Simpers of the University of Toronto, Kiran Vaddi of the University of Washington, and Robert Epps of the National Renewable Energy Laboratory, discussed their experiences developing and using laboratory techniques that do not require any human intervention.

Not all lab processes are suitable for full automation. It may not be worth it to automate experiments that are too short or too long, said Brown. “There’s a sweet spot in terms of experiment length,” he says.

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In 2016, Brown’s group began developing a self-driving lab based on 3D-printing for making and testing mechanical materials that can efficiently absorb energy. These materials might be useful in designing helmets or the crumple zone of a car, for example. Brown’s system consists of six 3D printers arranged in a circle with a robotic arm in the middle, along with instruments that can weigh and perform compression tests on the 3D-printed elements. They’ve named it Mama Bear, which stands for “Mechanics of Additively Manufactured Architectures Bayesian Experimental Autonomous Researcher.”

Brown’s research team tasked Mama Bear with finding a 3D-printed structure with optimal energy absorption efficiency. “Over the span of about two years of continuous study, we’re able to find structures that exceeded the limits that have been previously found,” he said.

Dunlap, collaborating with AFRL, now has a fully automated continuous flow setup for synthesizing small molecules and modifying polymers. This self-driving setup can explore solid state reactions and photochemical reactions, among others, and perform NMR measurements for testing. The researchers are moving toward updating the setup to be capable of high-throughput experiments.

The panelists emphasized the importance of using modular machines that run on open-source software. This allows researchers to assemble and customize components to make a self-driving lab for their scientific needs. Vaddi cautioned that the commercially available machines he uses for designing colloidal nanoparticles are becoming increasingly less open-source and more expensive. “We are trying to move away from these highly expensive systems and build low-cost modular hardware,” he said.

Hattrick-Simpers talked about how to assemble a team with the necessary skills and mindset to build these self-driving labs. People can sometimes have a “trust barrier” to automation, and it’s crucial that team members fully buy into the concept. Otherwise “you're not going to make a lot of progress,” he said.

In addition, building a self-driving lab requires an interdisciplinary team with “broad range and skill set,” said Epps. Hattrick-Simpers advised researchers to be realistic about what a single person can do. “You can’t expect one person to build the AI … and have the bandwidth to become a subject matter expert,” he said.

Several panelists have moved beyond simply showing that their systems work. Brown and Hattrick-Simpers are developing user facilities at Boston University and the University of Toronto, their respective institutions.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Giulia Grancini, Università degli Studi di Pavia

Hybrid Perovskite Solar Cells—A Game Changer for Near-Future Photovoltaics

Written by Elizabeth Wilson

In the past decade, perovskites have emerged as a promising material for solar cells. Current silicon-based solar cell production consumes lots of energy and is technologically intensive.

Perovskite solar cells sound almost too good to be true: with efficiencies of up to 26%, they self assemble from solutions, and production is scalable and less expensive. They're also recyclable and use 90% less energy in manufacturing compared with silicon-based cells. However, they have serious drawbacks that have so far thwarted industrial progress. They are unstable in moisture and heat, they have short lifetimes, and they can possibly release lead as they degrade.

At Wednesday's Symposium X—MRS/The Kavli Foundation Frontiers of Materials, Giulia Grancini, at the Universita degli Studi di Pavia, described her research group’s advances in hybrid perovskite solar cell designs.

A typical three-dimensional design consists of perovskite crystals and organic compounds. Scientists have found that a two-dimensional perovskite structure is more stable in water. But its efficiency is only 15%.

Grancini has been experimenting with hybrid perovskite solar cell designs that combine two-dimensional and three-dimensional perovskite structures, in an attempt to increase both efficiency and stability.

Much attention is now focused on the interface between layers of 2D and 3D materials, where the 2D layer protects the more efficient 3D layer from moisture in a phenomenon known as surface passivation. The industry standard lifetime for solar cells is about 25 years; Grancini's hybrid remained stable over a year of accelerated aging tests, which is more than 25 actual years.

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Recently, Grancini's group has been trying to understand how crystal orientation affects charge transport. The 2D perovskites form vertical columns aligned perpendicular to the substrate, which boosts charge transport.

Grancini hopes that new stability breakthroughs will come within a few years, moving the technology towards industrial use.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Róisín Owens, University of Cambridge

Advanced Tissue Engineering for In Vitro Drug Safety and Toxicology Testing

Written by Alison Hatt

In Tuesday’s Symposium X—MRS/The Kavli Foundation Frontiers of Materials, Róisín Owens of the University of Cambridge gave an overview of her work engineering tissues and integrating devices into cell and tissue models to probe electronic and ionic activity. The measurements can detect pathogens, reveal the impact of drug therapies, and interrogate tissue function, and the work broadly aims to improve in vitro models and accelerate drug discovery.  

Most of the work Owens discussed involved devices fabricated from conducting polymers, primarily PEDOT:PSS, which have both ion and electron conductivity and so can translate ionic signals to electronic and vice versa. Conducting polymers also have the great advantage of starting as a liquid, allowing Owens and her collaborators to construct devices in all manner of different shapes and sizes.

 

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She described several projects involving cell membranes, modeled by creating a supported lipid bilayer on the surface of a planar device like a multielectrode array, which can measure the membrane’s resistance and capacitance. Her laboratory used this technique to detect the entry of SARS-CoV-2 into a cell membrane, and to detect whether the virus was successfully blocked by a therapeutic antibody. They also used the technique to interrogate disparate parts of neurons, which can have very different morphologies and properties in different parts of the cell, observing the varying resistance due to changes in ion-channel density.

Stepping up a level in complexity, Owens described her work with barrier tissues next, in which ion flow is controlled by groups of cells. When those barriers are compromised in our bodies, pathogens can enter tissues and many diseases are connected to compromised barriers. Using a transistor device, Owens’s lab measured ion flow in a barrier tissue exposed to tumor-derived extracellular vesicles, which can fuse with healthy cells and spread cancer to them. They observed a change in resistance at the time of exposure due to a hypothesized change in cell morphology and could also observe the effect of a drug treatment, screening continuously to monitor its effect.

Owens also described her group’s work making 3D tissue models. Their strategy is to seed fibroblasts into a porous scaffold of PEDOT:PSS, where they excrete extracellular matrix, forming a sort of cyborg tissue. The researchers can then grow a layer of epithelium or endothelium on top of the membrane. In this manner, Owens’s research group has developed models for gut, brain, and lung tissue, building up stratified tissues with multiple components, allowing them to interrogate diseases and functions of those tissues. Using impedance measurements, the team can discern the signature of different tissue types.

 

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Measuring the impedance of intestinal epithelial tissue is useful for studying the gut microbiome and the connection between the gut and the brain. Owens showed results of an experiment where they added two types of live E. coli bacteria to the model and observed an increase in impedance, which indicated that the bacteria had strengthened the barrier.

Owens also discussed ongoing work to try and address human tissues ex vivo or in vivo with multielectrode devices. In one project, group members created an all-planar device for lung and gut models that can be placed atop existing tissue to measure its barrier properties. In another, her team developed a resistive strain gauge using PEDOT:PSS and PDMS to measure gut motility and neuronal activity of the gut’s muscle layer.

Looking forward, among other things, Owens is working toward developing patient-derived models to study diseases like IBS and MS, helping understand the role of the gut-brain axis and testing new therapies.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Takashi Taniguchi, National Institute for Materials Science

Hexagonal Boron Nitride Crystal Growth and Applications

Written by Rahul Rao

When is a diamond not a diamond? When a crystal with diamond’s properties is made not from carbon, but from boron nitride. In Monday afternoon’s Symposium X—MRS/The Kavli Foundation Frontiers of Materials, Takashi Taniguchi from Japan’s National Institute for Materials Science, spoke on his laboratory’s work with boron nitride crystals, spanning more than two decades.

Boron nitride comes in different crystal forms that shadow their carbon equivalents. Just as materials scientists can turn hexagonal graphite to cubic diamond at high pressures in the laboratory, they can transform hexagonal boron nitride (hBN) into cubic boron nitride (cBN) at around 5 GPa. Cubic boron nitride bears diamond-like hardness and wide-gap semiconductivity.

But where lab-grown diamonds have been a staple for decades, how to craft cBN is far less understood. Today’s cBN is still riddled with carbon and nitrogen impurities; one mysterious impurity causes cBN to absorb light in ultraviolet wavelengths. Taniguchi and his colleagues, then, took on the challenge of eliminating those impurities.

In the early 2000s, they found a promising impurity-culling solvent: Ba3B2N4. As it happens, growing cBN with Ba3B2N4 creates hBN as a byproduct. Although Taniguchi initially thought the hBN was largely unappealing waste, he changed his mind after discovering that the hBN had a very high purity.

 

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Around the world, researchers have used that hBN in some exciting applications. Engineers used hBN to make devices that emit ultraviolet light with wavelengths of around 215 mm. Researchers around the world found that they could use high-purity hBN as an excellent substrate for two-dimensional graphene electronics. More recently, researchers have realized that high-purity hBN can form effective quantum sensors. An array of hBN with boron vacancies is a recipe for useful magnetic field imagers.

Taniguchi and collaborators want to make even higher purity hBN. Their latest challenge is actually detecting those impurities: Secondary-ion mass spectrometry hits a detection limit around 10 ppm for carbon and 1 ppm for oxygen. So, they turned to electron spin resonance study. With this method and by tuning the solvent, Taniguchi could reduce carbon impurities to a few parts per billion. The result is that hBN-based ultraviolet light emitters can achieve efficiencies comparable to AlGaN light-emitting diodes.

Lastly, Taniguchi spoke about some of today’s hBN research directions. For instance, while their Ba3B2N4 solvent can work at atmospheric pressures, it is hardly ideal. Researchers are investigating other solvent metals, such as nickel. On its own, nickel isn’t a great improvement over Ba3B2N4, but by adding molybdenum, a solvent can work at 1 atmospheric pressure and 1200°C.

Additionally, researchers are now studying how to purge hBN of remaining oxygen impurities. At the same time, other researchers are experimenting with adding other types of impurities: different lanthanides can create a variety of color centers.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.


Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Symposium X Thursday_270x180Taeghwan Hyeon, Seoul National University

Designing Inorganic Nanomaterials for Energy and Soft-Electronics Applications

Written by Elizabeth Wilson

Taeghwan Hyeon is a prolific materials scientist, with over 400 publications and 74,000 citations under his belt. At Thursday’s Symposium X, Hyeon, who is with Seoul University, took his audience on a tour of recent highlights in his over-30-year career, including advances in fuel cell materials, and soft electronics for heart failure, while always stressing the importance of collaboration with his many colleagues.

Proton-exchange membrane fuel cells are the future of energy for transportation, Hyeon said. But the  catalysts required to produce hydrogen rely on rare, expensive platinum. “It’s impossible to get a good quality fuel cell electrode out of non-platinum materials,” he said. They key, then, is to use less of it, and increase its activity. Many groups are working on this issue. Hyeon’s group’s angle was to develop nanoparticles made of platinum iron alloys. However, the synthesis requires heating the nanoparticles, which causes the nanoparticles to coalesce into larger particles. Their solution was to coat the nanoparticles with polydopamine before heat treatment, which protects the particles, and they remain small. The result is a fuel cell that loses only 3% activity after 100 hours operation, a record high 10 times higher activity than some other similar catalysts. 

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Hyeon’s curiosity has also drawn him to materials with medical applications, in particular, heart failure. Heart disease is the leading cause of death in the U.S., and one third of those deaths are caused by heart failure. As a heart fails, it pumps less and less efficiently. Since the heart's activity is based on electrical impulses, soft-electronic materials that can be shaped around the organ hold promise to bolster the faltering activity of a failing heart. Hyeon’s groups took inspiration from recent work in which scientists transplanted a pig heart into a human. Although the patient survived only three months, it showed that pig hearts, which are similar to human hearts, can be used for experiments on soft-electronic materials.

Hyeon’s collaborative group first developed a stretchable, conductive cardiac mesh out of silver nanowires impregnated in rubber. They placed it on a rat heart, and showed the material could be used to pump blood over 50% more efficiently than the heart itself. Silver oxidizes easily, and the oxidized coating is not only toxic, it does not conduct. The group solved that problem by coating the wire with inert gold. They then wrapped the meshes around a pig heart. They were able to pinpoint areas where the heart was having problems, and apply electricity where it was needed.

Hyeon has many other irons in the fire, including the development of a photocatalytic enzyme that splits water to produce hydrogen. Current hydrogen production technologies are environmentally unfriendly, so his group is developing a catalyst that mimics the activity of a bacterial hydrogenase.

How does Hyeon manage such a wide variety of research projects? Collaboration, he said. “You cannot do it all.”

Other than his work, Hyeon's other passion is tennis. “I'm either in my office or on the tennis court,” he said.

Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.