Symposium X: Frontiers of Materials Research

Symposium X—Frontiers of Materials Research_iuliana-p-raduIuliana P. Radu, imec
How New and Old Materials Research and Know-How Extend the Increase in Computation Power

Written by Sophia Chen

Iuliana Radu of the Interuniversity Microelectronics Centre (imec), an institute dedicated to the research and development of nanoelectronics in Belgium, delivered a Symposium X lecture on Friday. Radu, a physicist by training, discussed how materials science can further increase computational power.

We currently live in an era where “the data center is the programming unit,” said Radu. People no longer store most of their data locally, instead piping it to a data center and processing it offsite. This has motivated the need for more powerful computation.

At imec, Radu and her colleagues develop the next generation of computers, where one approach is to shrink the transistor further. While researchers are studying a variety of materials and strategies for this, Radu’s presentation focused on a class of materials known as transition metal dichalcogenides. As a two-dimensional material—in other words, when the material occurs as a single atomic layer—transition metal dichalcogenides can make transistors smaller by shortening its so-called gate length, compared to when they are made from silicon.  One example of such a material is tungsten disulfide, which Radu has studied.

Radu described the current research on integrating these materials in transistors. One challenge is depositing them in stacked nanosheets on a substrate in a scalable process. Researchers are also studying the defects that occur in these materials.

In addition, researchers are considering how materials science can benefit future quantum computers. Radu anticipates this new type of computer, based not on transistors but on components known as quantum bits, or qubits, to be a paradigm shift for the field of computation, as they are capable of performing very different algorithms than classical computers.

Radu discussed two materials for making qubits—semiconductors and superconductors. Both types of qubit function at low temperatures near absolute zero, and the classical electronics that control the qubit will require materials that can function at these low temperatures.

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

Symposium X: Frontiers of Materials Research

Symposium X—Frontiers of Materials Research_yi-cuiYi Cui, Stanford University
Nanotechnology for Sustainability

Written by Sophia Chen

Yi Cui of Stanford University delivered a Symposium X lecture on Thursday. A materials scientist, Cui discussed nanotechnology applications in sustainability efforts, such as reduction of fossil fuel use and pandemic mitigation efforts. Just in his lab alone, they use nanotechnology to design better batteries, medical face masks, and clothing.

One thrust of his group’s research is “trying to reinvent the battery,” said Cui. Over the last 15 years, Cui’s group has tackled questions such as how to improve the energy density of batteries, how to extend their lifetime, how to reuse and recycle them, all while making sure the technology is safe. He sees his work as the next generation to lithium ion batteries, now in widespread use in portable electronics and electric vehicles, and whose pioneers received the Nobel Prize in 2019.

Cui has developed new batteries from higher energy density materials by optimizing the geometry of the materials inside the batteries. For example, his group has made lithium-ion batteries with anodes made of silicon nanowires instead of the conventional graphite. However, silicon poses design challenges, as it expands several times its original size as the battery discharges. This can cause the silicon nanowires to crack and break, so Cui’s group has developed a shell-like structure around the silicon to avoid the material fracturing. They have also made strides in developing lithium metal batteries—a “holy grail” for the field because of the metal’s theoretical energy density. But in reality, lithium metal is challenging to work with because the metal expands dramatically and breaks easily. To prevent this, Cui’s group has developed hollow nano-capsules for lithium metal to sit in.

His group has also developed new techniques for imaging the dynamics inside batteries. In 2016, they developed the technique of cryogenic electron microscopy, which freezes material and images the material at atomic-scale resolution.

Nanofibers can also make high quality air filters, such as those needed in medical face masks, said Cui. His group has achieved filters with 60% porosity made from fibers 10 µm in diameter, spaced apart by 15 µm. This produces a breathable mask using a tiny amount of material.

Clothing that cools or heats the wearer could also make a significant difference in energy consumption, said Cui. His group has designed a polyethylene textile that is more transparent to the infrared radiation produced by the human body compared to cotton. In tests, they found the material caused the wearer’s skin temperature to be nearly 3°C cooler than when the person was wearing cotton. He pointed out that changing heating or cooling by a single degree Celsius can, on average, alter energy usage by 10 percent.

It’s important to get these innovations in the hands of consumers quickly, said Cui. His company Amprius, founded in 2009, has commercialized the silicon nanowire anode battery technology. He has recently founded the startup Eenotech for commercializing the polyethylene material, whose spinoff company LifeLabs Design will sell a limited quantity of clothing made from the polyethylene material this summer.

At the end of 2020, Cui became the director of Stanford’s Precourt Institute for Energy. As director, Cui oversees a range of research spanning many fields. In addition to materials and other hard science research, the institute weaves together researchers studying sustainable finance, policy, human behavior, artificial intelligence, and more.

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

Symposium X: Frontiers of Materials Research

Symposium X—Frontiers of Materials Research_nick-roweNick Rowe, Centre National de la Recherche Scientifique
Tropical Rain-Forest Plants: A Source of Bio-Inspired New Materials, New Technologies and New Concepts

Written by Sophia Chen

Nick Rowe of the French National Centre for Scientific Research (CNRS) delivered a Symposium X lecture on Wednesday. Rowe, an evolutionary biologist, made the case that plants can inspire better robot design.

Rainforests, in particular, contain a wide variety of ingenious plant structures that help the organisms thrive in all three dimensions, as Rowe illustrated with photographs. Starting from the forest floor, he showed how a few square meters of a rainforest contained multiple trees with different root structures, including stilt roots, which prop up certain trees above ground resembling the legs of a tripod. Ascending to the forest canopy, Rowe also discussed different vines and other plants that climb trees to seek the sunlight above.

Technologies have much to learn from climbing plants, said Rowe. The stem structure alone of these climbing plants offers a wide palette of design recommendations. Some stems consist of concentric circles; others consist of layers of alternating composition between more rigid and more supple materials. Climbing plants also attach to other plants through a variety of structures, such as tendrils, sticky pads, hooks, sticky roots, and spines.

Rowe showed an example of a liana, a type of woody vine, that was climbing a tree. In the photograph, the tree had toppled, likely from a gust of wind—but the liana stem had survived and continued growing. Such climbing plants are “brilliant at surviving very high mechanical stresses and strains where other plants don’t,” said Rowe. These characteristics make them excellent sources of inspiration for technology applications, he said.

Rowe and his collaborators study the biomechanics of the plants as they grow. The research group is particularly interested in how these plants develop, such as a carabiner-like plant tendril that stays green and supple until it finds a twig to snap around, when it begins to become woodier. He and his team aim to catalogue the plants’ mechanical properties throughout their development. This information could serve as reference material for robotics engineers to pick and choose the plant-like properties they want for a specific application.

Researchers studying these plants draw on a rich history of knowledge. In fact, Charles Darwin composed a monograph On the Movements and Habits of Climbing Plants, while recovering from mental illness after writing Origin of Species, which experts continue to cite today, said Rowe.

Working with Patricia Soffiatti of the Federal University of Parana State in Brazil, Rowe has studied a climbing cactus with potentially advantageous characteristics for robotics. The cactus contains a hydrogel that can expand and contract to change the plant’s shape.

Rowe cautioned the audience about agricultural practices worldwide, such as land overuse and monoculture farming, that are destructive to rainforest plants. “All the marvelous structures we see in climbing plants—we will never see that again if the whole world takes this type of approach to growing green things on our planet,” said Rowe.

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

Symposium X: Frontiers of Materials Research

Frederick-mauFrederick Mau, Toyota Motor North America, Inc.
Intellectual Property Filing Strategy, Portfolio Management and Licensing of Material-Related Technologies

At Toyota, Frederick Mau aims to examine every idea for potential filing. He bases his decision on whether the invention is new, and if it is good for the company. According to the company, Mau took them from 28 US patents in 2006 to the cumulative number of 1,540 in 2016.

One of the recent patents Toyota holds is for omnidirectional structural color or pigment compounds that reflect specific wavelengths of light. The study began with modeling and then was taken to the laboratory which brought the company several patent files. Others accumulated in reference to this same invention due to improvements and new applications, so that the portfolio now contains 37 issued US patents.

Similarly, Toyota holds 64 issued US patents in their portfolio for nanomaterial synthesis and 33 issued US patents for bioactive cleaning materials. “When building a portfolio, not all the patents need to be huge and just kind of groundbreaking technology. There should be a few fundamental science,” Mau said, “but as you continue to work with the portfolio, you’re going to come across a lot of new improvements or applications and those can all be used.”

To file a patent, pointed questions need to be asked, Mau said, to help understand the various aspects of the invention, such as “What are the benefits?” “How does it work?” “Do you have data to back it up?” Data is essential, he said, particularly all of the empirical data.

With the increasing use of materials informatics comes new considerations for the patent attorney: “Who is the inventor?” “Can the resulting material be reproduced in a laboratory?” “What are the best routes for synthesis?” “Will the resulting material perform as predicted?” In the case of the pigment compounds, the simulations for the color pigments matched up to the laboratory results, so the patent process went well, Mau said, but this is not always the case.

After his presentation, Mau fielded numerous questions from the audience which can be viewed along with the presentation online through December 31st.

Symposium X: Frontiers of Materials Research

Reshma-shettyReshma Shetty, Ginkgo Bioworks, Inc.
Designing Biology

The onset of the COVID-19 pandemic may have heightened the general public’s awareness of two things: the dangers of biotechnology should someone release an uncontrollable virus as well as the marvels of biotechnology that enables researchers to rapidly (within a year vs 10 or 20 years) develop and distribute a vaccine. 

Reshma Shetty, co-founder of the synthetic biology company Ginkgo Bioworks, Inc. over 10 years ago, had been named at the same time by Forbes magazine as one of “Eight People Inventing the Future.” The future is here as Ginkgo Bioworks provides a bioengineering foundry to test and develop synthetic biology prototypes. Shetty said, “We design biology so that we can grow products rather than manufacture them.”

Among the projects Shetty described is a compostable plastic bag. The bag is made from a biological precursor (1,4 butanediol) that the E. coli bacterium had been engineered to produce. Other projects included the development of plant-based meats and designer bacteria crops that can fertilize themselves. These projects—all done in partnerships with other companies—contribute to building a bioeconomy.

To provide a sense of the enormous possibilities available in the emerging field of synthetic biology, Shetty displayed a metabolic map, giving a snapshot of different types of chemistry reactions that occur inside living organisms. The map shows tens of thousands of enzymes that can catalyze a reaction. “By simply selecting or engineering the right enzyme sequence, you can create exquisitely interesting new manufacturing methods using biology,” Shetty said. 

However, well aware of the public’s general distrust of biotechnology, Shetty’s company embarked on a project with the hopes of piquing their interest instead. Inspired by the movie Jurassic Park, Shetty’s group wondered what it would be like if visitors in a museum could smell an extinct plant. The way to go about this was to identify a plant that has recently become extinct so that they could still obtain samples. They chose the Mountain hibiscus (Hau Kuahiwi). They found a sample at Harvard University. From the very small sample, they were able to obtain fragments of DNA that they stitched together based on what they know from a particular class of enzymes in living plants that make fragrance compounds. “We made sort of a ‘part science-part artist’ rendering of what we think the Mountain hibiscus smelled like,” Shetty said. “The point of the project was not to scientifically recreate the scent of an extinct plant but really to help inspire the imagination for folks about what biology could do.” The research group distributed displays of their work to museums around the world.

Symposium X: Frontiers of Materials Research

Daniel G. Anderson, Massachusetts Institute of Technology

Biomaterials for the Therapeutic Delivery of Nucleic Acids, Genome Editing Tools, and Cells

“The first major area I’d like to discuss,” said Daniel G. Anderson, “is where we will get to talk about making drugs that can actually repair your DNA while you’re still using it.” This is the stuff of science fiction, he said, except that this work is real. “Imagine a nanoparticle that you might inject into your blood … that can travel through the body, reach that diseased liver, actually enter those cells, deliver therapeutic [treatment] that can specifically repair the DNA,” he said, and permanently repair the disease. One of the challenges, Anderson said, is how to get the nucleic acids or genome editing tools inside the body.

Certain organs are more amenable, he said. For example, the blood vessels in liver have small holes that allow nanoparticles inside. Nanoparticles can be made to carry nucleic acids that can encode different parts of the genome editing machinery. But turning nucleic acids into drugs is not easy, he said. In one example Anderson described success with RNA-lipid nanoparticles that could turn off the TTR gene to treat the liver which would replace the need for a liver transplant. In 2018, the first siRNA lipid nanoparticle was approved by the FDA.

For a detailed discussion of Anderson’s work on gene suppression with siRNA, gene expression with mRNA, permanent genetic editing using the CRISPR/Cas9 system, and on creating a cellular factory that can create drugs on demand, watch Anderson’s presentation online, available through December 31st.

Symposium X: Frontiers of Materials Research

F18_building_an_inclusive_ortiz_photoChristine Ortiz, Massachusetts Institute of Technology and Station1
Socially-Directed Science and Technology

MIT Professor and Co-founder of a non-profit higher education institution called Station1 based in Lawrence, Massachusetts, Christine Ortiz is leading the development of a new model of frontier learning and research—socially-directed science and technology. This exciting initiative, launched in collaboration with Co-founder and historian of science and technology also at MIT, Dr. Ellan Spero, is based upon a foundation of inclusion and equity; this model integrates science, technology, engineering, and math (STEM) with humanistic fields at a granular level in order to interrogate, understand, and shape technologically-driven societal impact towards more equitable, ethical, and sustainable outcomes.

Station1 delivers transformative education, research, and innovation programs and leads higher education systems change initiatives. The Station1 Frontiers Fellowship is a prestigious, fully-funded ten-week summer experience for undergraduate students that involves socially-directed science and technology education, research, and innovation. Unique in the nation and the world, the SFF includes an exciting research internship in emerging areas of science and technology, a cross-interdisciplinary shared curriculum on socially-directed science and technology, and personal and professional advancement activities. Approximately all of the Station1 Fellows alumni are from low income backgrounds, minoritized groups, and/or first generation to attend college.

To describe these concepts in her presentation, Ortiz posed the question, “How can we re-think the fundamental process of research that have enabled environmental and social inequities?” The field of materials science and engineering has contributed enormous benefits to society in, for example, medicine and healthcare, computation, transportation, infrastructure, and energy and, yet, has also been deeply entangled with social inequities and injustice. Examples discussed included materials, the Anthropocene, and environmental injustice focused on Louisiana’s Mississippi River, materials, racial and social inequity, and disparate risks to fire, shipbreaking, global interconnectedness, and social life cycle assessment.

At Station1, the work of the students does not take place on a college campus separate from the social inequities they’re entangling in their research but rather in a post-industrial mill town (Lawrence) where they are doing primary research on the infrastructure. Ortiz said, “We have students look at all kinds of materials and infrastructure outside in Lawrence and think about the embedded social structure to those technological systems that are still there today.”

The well-known tetrahedron of structure-properties-performance-synthesis & processing now embeds “society” in the center. Part of this approach is to reformulate research questions. “We have students actually look at literature scholarship from both the science and engineering field and humanistic field and put them into conversation with each other,” said Ortiz, “and think about ‘how can we leverage the best of both of these?’”

At MIT, Ortiz co-leads two educational projects called “Materials, Societal Impact, and Social Innovation,” and “The Social Life of Materials: Past.Present.Future” where students research the broader social context of historical and emerging materials technologies. The purpose of this educational approach is to prepare students to engage in scientific research and engineering in a way that fosters a more equitable and sustainable future.

Symposium X: Frontiers of Materials Research

Anke-weidenkaffAnke Weidenkaff, Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS

Efficient Recycling and Regeneration of E-Mobility Components and Materials

While the digital world has enabled virtual conferences such as this one—enabling the sharing of research results and networking among scientists during a pandemic—“digitalization” also comes with problems that affect the environment.

Anke Weidenkaff, executive director of the Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS in Germany, laid out the problems and possible solutions for sustainable technology and the role of materials.

Digitalization, she said, decreases the lifetime of devices. For example, when the circuit board now found in appliances such as a washing machine breaks, the whole machine is broken and now removed to the trash. Also, devices such as cell phones become quickly out-of-date, thus adding more products to the e-waste pile. In the future, Weidenkaff said, our cars and houses will be completely digitalized and quickly outdated, which puts the problem on a very different scale than small devices such as a cell phone.

Digitalization also leads to dissipation of strategic metals, which will have consequences for energy conversion processes, for example in electronic vehicles, or “e-mobility.” “We have to find solutions to recover strategic metals as soon as possible and also to design products so this dissipation will not take place in the future,” she said.

To achieve a zero-waste society, the current recycling paradigm—for example, for Li batteries—is inefficient because it creates more waste. “One possibility,” Weidenkaff said, “is to regenerate or self-heal the material, or to develop smart materials which can be converted without the deposition of waste.” At Fraunhofer IWKS, two approaches are being studied. In one approach, parts are automatically sorted with the help of sensors and separation technologies. “We are using artificial intelligence to increase the sorting procedure,” Weidenkaff said. The other approach involves electro-hydraulic fragmentation. Components made from recycled materials will then lead to the production of “green” products that will prevent resource problems in the future. More information can be found at the Fraunhofer IWKS website.

Weidenkaff also detailed the materials challenges involved with the recycling of high-performance permanent magnets which are predominant in electronic devices, and the materials challenges for achieving a hydrogen economy. To combat climate change, researchers need to develop a new way of thinking. For example, to substitute critical metals in magnets, researchers need to embark on a holistic evaluation of what criteria is needed from a material. They need to consider the material from an ecological, economics, supply availability, efficiency, durability, programmability, and multifunctionality approach. A new criteria, Weidenkaff said, would be a material that can be decomposed rapidly and reused elsewhere but at the same time is stable for its current use in a product.

“Smart materials can become very sustainable if they know what to do,” she said, “if you can tell them to ‘decompose yourself.’”

Symposium X: Frontiers of Materials Research

Vijay-narayananVijay Narayanan, IBM T.J. Watson Research Center
The Golden Age of Materials Innovations—From High-κ/Metal Gate to AI Hardware

In his early days at IBM, Vijay Narayanan introduced new materials at the nanoscale to incorporate into the core of the transistor in order to enable computers to work rapidly at low power. With the advent of deep learning-based artificial intelligence algorithms, materials innovation is required again. Currently, the research community is working under the idea that artificial neural networks can be mapped to arrays of non-volatile memory (NVM) elements. The NVM elements being evaluated as resistive processing units are falling short. Narayanan says innovation and collaboration across academia and industry is necessary to overcome this obstacle.

Complementary metal oxide semiconductor (CMOS) chips have reached the third generation in development in which fin field-effect transistor (finFETs) are fabricated through extreme ultraviolet lithography (EUV). The next step in the semiconductor technology roadmap is scaling down to 5 nm node and beyond through R&D in nanosheet device architectures.

For the next phase in semiconductor R&D, Narayanan said, “Materials scientists have had the opportunity to now impact a totally new era of AI compute.” In his talk, Narayanan concentrated on analog AI, “which is the concept of using nonvolatile memory elements crossbar arrays for deep learning acceleration.”

Deep learning has become essential because the amount of data available has increased exponentially, Narayanan said. Furthermore, with the deep learning explosion, in 2014 to 2015, accuracies in image recognition are better than what humans can do, and likewise with speech recognition. “This can be a significant benefit for the entire AI computer ecosystem,” Narayanan said. And now, due to machine learning, new technology and new paradigms are needed to absorb the emerging workloads.

Materials innovation comes into play in regards to new architectures for AI to help “consume the workloads and help map deep learning networks into something that can be energy efficient,” Narayanan said. It will be critical for materials researchers to collaborate with algorithmic teams early on in the R&D of AI hardware.

Narayanan’s presentation will be available online through December 31, 2020.

Symposium X: Frontiers of Materials Research

Symposium X Alessandra Lanzara_800x800Alessandra Lanzara, University of California, Berkeley, and Lawrence Berkeley National Laboratory

Engineering Two-Dimensional Heterostructures with a Twist 

Written by Arthur L. Robinson

The past few years have seen exciting new opportunities emerging from simply stacking and/or twisting together atom-thick layers of the same or different materials. The lattice mismatch or rotational misalignment introduced by such stacking gives rise to long-range Moiré patterns that lead to modification of the electronic band structure, which in turn gives rise to the appearance of unexpected properties, such as Mott-like behavior and superconductivity, even in weakly interacting systems such as graphene.

In her Thursday Symposium X presentation, Alessandra Lanzara of the University of California, Berkeley, and the Lawrence Berkeley National Laboratory described recent investigations by her group on twisted and strained graphene and transition metal dichalcogenide (TMD) heterostructures as a function of twisting angle and gating. Using angle-resolved photoemission spectroscopy, the group studied the effect of such misalignments on the electronic structure of these materials, yielding insight on the key parameters that lead to the onset of strong correlation and novel behavior in these materials.

Lanzara opened her talk by introducing the importance of topology as an essential theoretical tool in understanding the properties of materials. Until recently, thinking about transitions in crystalline solids has been based on order parameters related to symmetry breaking and correlations. Topology has now joined these as an organizing principle of matter. In general, topological properties are those that are preserved under continuous deformation. For example, in a topological insulator there is no sharp phase transition, but the insulator property is preserved as the electronic band structure is continuously deformed.

Symposium X Alessandra Lanzara 2_800x800

With the addition of topology, said Lanzara, it is now possible to describe the various states of materials now on a single diagram with a correlation energy on one axis and the spin–orbit coupling on the other. Close to the origin, conventional metals and insulators are well described by band theory. As the correlations increase, Mott insulators come to the fore, whereas topological insulators and semimetals come to the fore when spin–orbit coupling increases. But the future may lie in the panoply of exotic behaviors like Weyl insulators that arise as both correlations and spin–orbit coupling grow.

“What new cooperative phenomena and particles will occur when you bring together correlation, spin orbit coupling, and topology?” Lanzara asked next. Taking a hint from physicist Richard Feynman’s famed questions about two-dimensional pages, the question became “What would the properties of materials be if we could really arrange the atoms the way we want them?” But how would one go about exploring this immense space? One way to arrange atoms is by means of heterostructures consisting of stacks of materials with different properties with relevant aspects being dimensionality, coupling to the lattice, order (spin, charge, orbitals, and Cooper pairs in superconductors), and electrostatic doping. Outcomes of building these structures include emergent phenomena at interfaces, such as ferromagnetism, superconductivity, and metal-to-insulator transitions.

From here Lanzara rapidly reviewed some considerations, such as electron screening, and methods for controlling the electronic structure in the context of searching for new phenomena. In particular, her group found that twisting the layers in the heterostructure provided a new level of band-structure control. In fact, when Lanzara was being introduced as the speaker for this Symposium X, the MC used the term twist-tronics.

After discussing engineering of topology and strong correlation, including local inversion-symmetry breaking in the heterostructure layers that gives rise to spin–orbit coupling, Lanzara turned toward the possibility of an even larger phase space for materials design, moving from periodic crystals with both long- and short-range order, to quasiperiodic crystals with order but are not periodic, to Floquet crystals that are periodic in time, and ending with amorphous materials with no long-range order but perhaps some short-range order. After asking if amorphous systems can be used for materials engineering, she reported some early results on the amorphous topological insulator Bi2Se3. One task was to find a replacement for the momentum quantum numbers (kx, ky, kz) in crystals. The group was thinking of an (average) bulk Hamiltonian as spherically symmetric in k-space, resulting in a wavefunction parameterized by k2 and the angles q and f in a spherical coordinate system.

Lanzara summed up her presentation by declaring that two-dimensional heterostructures constitute an incredible, highly tunable platform for exploring correlation, symmetry breaking, and topology. The electronic structure of two-dimensional van der Waals materials is extremely easy to modify, including effects such as symmetry breaking to induce gap opening and renormalization effects due to screening, and spin–orbit coupling and other many-body interactions. But questions still ripe for investigation include: Can we design new types of many-body topological properties and new particles? And what new phases can result from the interplay between them?

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