MRS Bulletin Materials News Podcast

In this podcast episode, MRS Bulletin's Laura Leay interviews Harry Atwater from the California Institute of Technology about his study on lightsail propulsion in order to understand how the device can be developed to do fly-by space travel riding a beam of laser light. Atwater's research group made a square prototype device where the researchers incorporated springs at each corner, etched out of a single sheet of silicon nitride, fastening it to the support frame. They tested its behavior in a two-beam interferometry experiment. Their comprehensive analysis provides a thorough understanding of key parameters that are essential for lightsail propulsion and paves the way for the next step of research: untethered flight. This work was published in a recent issue of Nature Photonics.  

In this podcast episode, MRS Bulletin's Laura Leay interviews Ashwin Shahini and Alan Taub from the University of Michigan about their group's simulations and experimental work detailing the formation mechanisms, morphologies, and microstructures of an in situ Al/TiC metal matrix nanocomposites processed via salt flux reaction. Using these insights, the microstructure of a material can be tuned in order to optimize the materials properties. While the three-dimensional imaging is critical to gaining insight into the structure, computational models can facilitate this optimization. This work was published in a recent issue of Acta Materialia. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Xingchen Ye of Indiana University about his research group's studies on the fundamental behavior of colloidal materials. Colloidal materials consist of liquids with nanoparticles suspended in them. Ye's team is interested in how a colloidal material's properties change as the team spatially rearranges the nanoparticles in the liquid. They looked specifically at the self-assembly of gold nanocubes into a lattice structure. Ye's team studied how that structure gives rise to the material's bulk properties. This work was published in a recent issue of Nature Chemical Engineering.

In this podcast episode, MRS Bulletin's Laura Leay interviews Fabian Meder from the Italian Institute of Technology in Genova and the Sant'Anna School of Advanced Studies in Piza, Italy about his research group's device that makes use of wind-driven plant leaf motion to generate electricity which can power a chemical delivery system. Their triboelectric nanogenerator involves an artificial leaf made of a 500 μm silicone elastomer layer and an electrode made from indium tin oxide. This is attached to the leaf of a plant. A gold-coated pin electrode inserted in the stem of the plant harvests charges from the plant tissue. This work was published in a recent issue of Bioinspiration & Biomimetic. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Bowen Deng, a graduate student in Gerbrand Ceder's group at the University of California, Berkeley, about their work on increasing the accuracy of artificial intelligence/machine learning materials prediction models. The use of computer simulations to predict the interaction between atoms in a given molecule is being replaced by machine learning. Researchers describe the atoms' collective interactions as a quantity of energy, where higher energies correspond to stronger forces holding the molecule together. Now, Deng's research group studied three machine learning models and found that they tend to predict lower energies than what is accurate by about 20 percent. The researchers have determined that these underpredictions were caused by biased training data and they found a way to remedy the situation. This work was published in a recent issue of NPJ Computational Materials.

In this podcast episode, MRS Bulletin's Laura Leay interviews David Cahen from the Weizmann Institute of Science, Israel, about the impact surface defects have on bulk properties, specifically in the case of lead halide perovskites. In a perspective he co-authored, Cahen connected numerous experimental data from other researchers that exposed this phenomenon. By understanding how surface defects control the material's electronic behavior, researchers can pursue new materials for the development of long-lasting devices. This work was published in a recent issue of Advanced Materials. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Gwangmin Bae of Korea University about his work with colleagues on the design of a new smart window system that utilizes compression. Like other smart windows, this window makes use of pores within the material to adjust its transparency. However, instead of using a stretchy material that controls light scattering through the pores, Bae and colleagues used a material that compresses in thickness. That is, the window becomes more transparent when it is compressed. The researchers place this structured porous material made of the polymer polydimethylsiloxane or PDMS between two panes of glass to create the smart window. This work was published in a recent issue of Nature Communications.

In this podcast episode, MRS Bulletin's Laura Leay interviews Leif Asp of Chalmers University of Technology about his group's development of an all-carbon fiber-based structural battery. The negative electrode uses carbon fiber and, for the positive electrode, the carbon fiber is coated with lithium iron phosphate. In both cases the carbon fiber takes on the roles of mechanical reinforcement and current collection. This work was published in a recent issue of Advanced Materials.

In this podcast episode, MRS Bulletin's Laura Leay interviews Nancy Sottos, the Maybelle Leland Swanlund Endowed Chair and head of the Department of Materials Science and Engineering at the University of Illinois–Urbana Champaign (UIUC), and Justine Paul, a former student at UIUC who now holds a position at DuPont, about their work with frontal polymerization. By mimicking patterns in biological materials such as shells, their research group took a multidisciplinary approach to control crystalline patterning, which ultimately enabled them to control mechanical properties of polymers. By applying heat, they made slight changes in the chemical reactions to achieve specific crystalline patterns. This work was published in a recent issue of Nature.

In this podcast episode, MRS Bulletin's Laura Leay interviews Reza Moini of Princeton University about his group's development of an enhanced additive manufacturing technique to fabricate cementitious materials with excellent fracture toughness. They based their design of the material on the double-helical or double-bouligand structure of coelacanth fish scales that resist deformation. In order to fabricate the material, Moini's research team used a two-component robotic additive manufacturing process. The extrusion system was controlled using specialist algorithms. This work was published in a recent issue of Nature Communications.

In this podcast episode, MRS Bulletin's Sophia Chen interviews postdoctoral research fellow Rohit Pratyush Behera and Prof. Hortense Le Ferrand of Nanyang Technological University in Singapore about their design of a strong and tough ceramic that absorbs energy, inspired from biology. They borrowed microscopic designs found in a mollusk, a mantis shrimp, and the enamel casing surrounding human teeth. The researchers stacked round discs of aluminum oxide particles in horizontal layers in a helical structure, then encased the structure in an extra protective layer made of alumina nanoparticles. The aluminum oxide in the discs is designed to respond to an external magnetic field, modifying the orientation of the discs layer by layer, consequently adjusting the properties of the ceramic composites. This work was published in a recent issue of Cell Reports Physical Science.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Yen-Hung Lin of Hong Kong University of Science and Technology about his work to eliminate defects in perovskite solar cells. Lin's group treated the perovskites with a category of molecules known as amino-silanes, which bind vacancies in the perovskites, preventing recombination of the electrons and holes. The amino-silane treatment retained the device's performance at 95% power conversion efficiency for more than 1500 hours. This work was published in a recent issue of Science. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Michael Pettes, deputy group leader and staff scientist at the Center for Integrated Nanotechnologies in Los Alamos National laboratory about a characterization technique that employs a four-dimensional scanning transmission electron microscope (4D-STEM) paired with complex computational data analysis to directly measure the thermal expansion coefficient (TEC) of monolayer epitaxial tungsten diselenide. The standard technique for directly measuring the TEC involves X-ray diffraction, but 2D materials are too thin. 4D-STEM uses a patterned electron probe which enables diffraction positions to be accurately mapped in real space. This method overcomes the challenges of indirect measurements and spatial resolution. This work was published in a recent issue of ACS Nano. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Michael Dickey of North Carolina State University about the discovery and mechanical properties of glassy gels. Dicky credits his postdoc Meixiang Wang who, while studying ionic liquids, created the first glassy gel. Dicky's group found that the mechanical properties of their glassy gel include shape memory, self-healing, and adhesion. While other materials may demonstrate comparable toughness and stretchiness, the glassy gel offers an advantage because of its simple curing process. This work was published in a recent issue of Nature. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Coskun Kocabas from The University of Manchester in the UK about his development of a metamaterial that can tailor thermal emission. Rather than using a periodic system, which most topological materials employ, his research team borrowed a concept from laser design and created an optical cavity using a dielectric medium sandwiched between two layers that act as mirrors: a metal substrate and a top layer of platinum. The top layer serves as a thermal emitter, and the thickness of the top layer defines the topological property that regulates thermal emissivity. This work was published in a recent issue of Science. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Rasmus Neilsen from the Technical University of Denmark about his fabrication of a monolithic selenium/silicon tandem solar cell. The selenium forms the top cell of the tandem device, with silicon used as the bottom cell. Selenium-based single-junction solar cells have traditionally used fluorine-doped tin oxide. In this work indium-tin oxide was used as a transparent conductive layer that is easier to deposit and its use is more widespread. Neilsen and his research team controlled the thickness of the carrier-selective contacts in the silicon solar cell that protects the silicon layer from the processes used to deposit subsequent layers on top, thus enabling them to deposit the top cell directly onto the substrate. This work was published in a recent issue of PRX Energy. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Mihir Pendharkar of Stanford University about characterizing electronic properties of twistronics materials. Twistronics refers to a type of electronic device consisting of two-dimensional materials layered at a relative twist angle, forming a new periodic structure known as moiré superlattices. Pendharkar and colleagues studied different configurations of graphene layered with hexagonal boron nitride. Determining the twist angle of any particular sample is extremely time-consuming. By developing a characterization technique called torsional force microscopy, Pendharkar and colleagues have reduced the time to a matter of hours. This work was published in a recent issue of Proceedings of the National Academy of Sciences. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Falon Kalutantirige from the University of Illinois Urbana-Champaign and Ying Li from the University of Wisconsin-Madison about their approach and discovery when characterizing nanovoids in polymer films. Using polyamide (PA) membranes as their subject of study, the researchers applied graph theory combined with electron tomography and molecular dynamics simulations to characterize the morphology of the nanovoids. The key to understanding permeance of the membranes lies in understanding the void space that was mapped using electron tomography. Using their mixed-method approach, the researchers were able to relate the nanoscale morphology to membrane function. Taking this beyond the study of PA membranes, the research team showed how nanovoids impact the synthesis‒morphology‒function relationships of complex nanomaterials. This work was published in a recent issue of Nature Communications. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Alexandre Dmitriev from the University of Gothenburg, Sweden about his group's computational model of a three-dimensional metamaterial exhibiting a magnetoelectric effect—known as the Tellegen effect—when exposed to light. The building blocks of the metamaterial are comprised of disks of silicon, 150 nm in diameter, supporting a cylinder of cobalt. Silicon is chosen for its high refractive index and cobalt for its magnetic properties. These building blocks are randomly distributed in a host medium such as water or a polymer. The metamaterial has applications in areas such as improving the efficiency of solar cells, creating one-way glass, or improving lasers. It also has the potential to revolutionize how the universe is understood and could hold the key to studying dark matter. This work was published in a recent issue of Nature Communications.

In this podcast episode, MRS Bulletin's Laura Leay interviews Antonio Dominguez-Alfaro from the University of Cambridge, UK about the development of a single-step manufacturing approach for a multimaterial 3D-printing method. The research team created two inks. One ink is a polymeric deep eutectic solvent – polyDES – made by combining and heating two salts to form a deep eutectic monomer and adding a photo-initiator to allow the ink to be cured. This ink is an ionic conductor so can capture signals from neurons inside a biological system. The other ink was based on the polymer Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), which is commonly used in bioelectronics as a mixed electronic and ionic conductor. The work resolves many challenges of applying additive manufacturing in the field of bioelectronics. This work was published in a recent issue of Advanced Science. 

In this podcast episode, MRS Bulletin's Elizabeth Wilson interviews postdoctoral researcher M. Iqbal Bakti Utama of Northwestern University about a method allowing single photon production without defect. Aryl diazonium chemistry has been used in the past to functionalize the surface of carbon nanotubes. Utama's group found that this chemistry also works for tungsten diselenide surfaces. The group immersed tungsten diselenide monolayers into an aqueous solution of 4-nitrobenzene-diazonium tetrafluoroborate. The electrophilic molecules withdraws electrons from the monolayer, creating aryl diazonium radicals. These radicals react with each other to form nitrophenyl oligomer chains. Instead of binding covalently to the monolayer surface, the oligomers form an adlayer that is physisorbed on the tungsten diselenide surface. The spectra of photons generated when the research team irradiated the coated surface was vastly simpler than the uncoated monolayer. This work was published in Nature Communications.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Irmgard Bischofberger of the Massachusetts Institute of Technology about her investigation of how chirality emerges in nature. She uses liquid crystal molecules of disodium chromoglycate in her studies. When the molecules are dissolved in water, they form linear rods. The research group then forces the rods through a microfluidic cell, causing the rods to assemble into spiral structures without mirror symmetry. The achiral structure transformed into a chiral one. What is unique, says Bischofberger, is that the new material is composed of non-chiral building blocks. This work was published in a recent issue of Nature Communications. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Eric Pop, Xiangjin Wu, and Asir Intisar Khan from Stanford University about their work building a phase-change memory superlattice at the nanoscale. They created the superlattice by alternating layers of antimony-tellurium nanoclusters with a nanocomposite made from germanium, antimony, and tellurium (GST467). Each layer is ~2 nm thick and the superlattice consists of 15 periods of these alternating layers. The microstructural properties of GST467 and its high crystallization temperature facilitate both faster switching speed and improved stability. The device operates at low voltage and shows promise for high-density multi-level data storage. This work was published in a recent issue of Nature Communications. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Magalí Lingenfelder from the École Polytechnique Fédérale de Lausanne, Switzerland about her group's discovery of the switching mechanism behind H-bond-linked two-dimensional networks. The hydrogen bonding ability was tuned by comparing carboxylates to aldehydes. Lingenfelder's group found that the ability of the structure to switch between an open structure to a close-packed one is governed by a synergistic combination of energetic contributions from both the adsorbate/adsorbate and absorbate/substrate interactions. This work was published in a recent issue of ACS Nano. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Aram Amassian from North Carolina State University about his group's achievements using RoboMapper, a materials acceleration platform. In researchers' quest to run environmentally-conscious laboratories, Amassian offers a solution that focuses on characterization of materials. Having found that characterization generates a lot of energy, his group developed an automated approach to screening small samples in order to identify ones that warranted more in-depth study. By using their automated approach, the researchers found quantitative structure–property relationships for wide-bandgap perovskites. This work was published in a recent issue of Matter.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Kaveh Ahadi from The Ohio State University about a material his group developed that maintains superconductivity in a magnetic field. The researchers grew a film of lanthanum manganite on a crystal of potassium tantalate. When lowered to the temperature of 2 Kelvin, the material is a superconductor. When Ahadi's group applied 25 Teslas of magnetic field, the material stayed superconducting. Even though the material is not of practical use, Ahadi says that studying this material will help researchers better understand the mechanisms that lead to superconductivity. This work was published in Nano Letters. 

In this podcast episode, MRS Bulletin's Elizabeth Wilson interviews Manos Mavrikakis from the University of Wisconsin–Madison about his group's theoretical work on real-world industrial catalytic conditions. It is often assumed that most catalyst surface atoms stay in place during a reaction, firmly bonded to their metal neighbors. However, Mavrikakis's theoretical framework shows that under industrial reaction conditions, a surprising amount of metal–metal bond breaking is likely happening during catalytic reactions. This framework predicts that under reaction conditions, some adsorbed molecules have the strength to scavenge metal atoms from the catalyst particle, causing metal atoms to be ejected to a different spot on the metal surface. Bonds between metal atoms in certain geometries such as kinks can also break, even without adsorbed species, due to heat. However, the presence of reaction molecules may greatly increase the frequency of these events. The ejected metal atoms can then move around on the surface, collect together into groups such as trimers, tetramers, hexamers, or larger ensembles, forming entirely new types of active sites. This work was published in Science.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Nathan Gabor from the University of California, Riverside about his group's work on imaging and directing the flow of electrons in electronic devices. They designed their device by taking a crystal of yttrium iron garnet, which does not conduct electricity, and putting a nanometers-thick layer of platinum, which does conduct electricity, on top of it. When they illuminate the device with a laser, this device produces an electric current. They further discovered that when they combine the crystal with the platinum, the interface between the two materials exhibits magnetic properties. Gabor's research team used this sensitivity to a magnetic field to steer the electron flow in the device. This work was published in Proceedings of the National Academy of Sciences.

In this podcast episode, MRS Bulletin's Rahul Rao interviews Fereshte Ghahari of George Mason University about the use of a scanning tunneling microscope (STM) to measure the electronic and magnetic properties of moiré quantum materials. Ghahari and collaborators twisted two layers of graphene at a specific angle, then chilled the material to suppress as much motion as possible. They ran an STM across the material while varying the magnetic field. They could precisely observe how those field changes affected the energy levels of the electrons, realizing that they could use those discrete energy levels as a “quantum ruler.” “We hope these new measurements help researchers to optimize these magnetic and electronic properties of quantum materials for specific applications,” says Prof. Ghahari. By manipulating the electrons in moiré quantum matter and shifting its twist angles, materials researchers may be able to improve on materials that are useful for microelectronics or superconductors, for example. This work was published in a recent issue of Science. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Hamideh Khanbareh and Vlad Jarkov of the University of Bath in the UK about an application they introduced for using piezoelectric materials in tissue engineering. The researchers fabricated a composite by combining polydimethylsiloxane with a piezoelectric material of potassium-sodium-niobate that is compatible with cell lines similar to neurons. They then studied how the composite material would interact with neural stem cells. They found that the piezolectrically activated composites allowed the cells to spread across the surface of the material and saw an increase in the amount of neurons. Usually the use of piezoelectric materials in tissue engineering requires mechanical stimulation from either movement of the body or the application of ultrasound. In this research, no additional mechanical stimulation was required. This work was published in a recent issue of Advanced Engineering Materials. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Professor Jerry Qi and postdoctoral researcher Mingzhe Li of the Georgia Institute of Technology about their new technique to 3D print silica glass. After using two-photon polymerization to cross-link poly-dimethylsiloxane, Qi's research team used deep UV to convert the polymer into silica glass. The deep UV irradiation is carried out in an oxygen-rich atmosphere. The UV light converts the oxygen to ozone, which then reacts with the polymer, prompting the formation of silica glass. Furthermore, printing of the silica glass is accomplished at the low temperature of 200°C, compared to 1000°C required for current methods of 3D printing. Qi's group fabricated structures of several tens of micrometers in size, with a resolution of a few hundred nanometers. This work was published in a recent issue of Science Advances.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Surabhi Madhvapathy of Northwestern University about an implantable bioelectronics system that can perform early detection of kidney transplant rejection in rats. Madhvapathy and her colleagues have developed a wireless sensor that attaches to the kidney itself. The biosensor measures the organ's temperature and its thermal conductivity. These can point toward inflammation in the kidney, which can be a sign of organ rejection. This work was published in a recent issue of Science.

In this podcast episode, MRS Bulletin's Laura Leay interviews Kento Katagiri, a postdoctoral scholar at Stanford University, about the propagation speed of dislocations in materials. Using an X-ray free electron laser to collect data from single-crystal diamond, Katagiri and colleagues have determined the velocity of wave propagation to be in the transonic region. Katagiri's work is most applicable to extreme shock events such as missile strikes and shuttle launches where pressures of one terapascal or more might apply. The results are relevant to a type of nuclear fusion known as Inertial Confinement Fusion, which uses intense lasers to compress the fuel. This work was published in a recent issue of Science.

In this podcast episode, MRS Bulletin's Laura Leay interviews Stanford University's Jennifer Dionne and her PhD student Fareeha Safir and their colleague Amr. Saleh from Cairo University about their work on identifying bacteria in complex samples. Instead of culturing bacteria then identifying them using specific methods such as a polymerase chain reaction test, which takes hours, Dionne's research group uses Raman spectroscopy combined with machine learning to detect the presence of two specific bacteria in samples that contained red blood cells. The addition of gold nanorods to the samples further enhanced the signal from the bacteria. Another way the research team accelerated the detection of bacteria signal was by building an acoustic bioprinter for the liquid samples: the specialist printer uses focused soundwaves to break the surface tension of a larger droplet, maintaining cell viability. This work was published in a recent issue of Nano Letters.

In this podcast episode, MRS Bulletin's Sophia Chen interviews Alice Soragni of the University of California, Los Angeles about her work in precision oncology. Rather than sequence the DNA of a patient's tumor, Soragni uses bioprinting to create organoids from the patient's cells. She then adds various drugs to the cells to directly test their response to each drug. To check the effectiveness of the drugs, Soragni's group measures the organoid's mass with a technique called interferometry. Interferometry is a non-invasive technique that involves shining light on the cells to monitor their response to the drug. This process allows Soragni to characterize the organoid's response to the drug in fine detail. This work was published in a recent issue of Nature Communications. 

While thermodynamics suggests that water sorption is more favorable at a low temperature, MRS Bulletin podcaster Laura Leay interviews post-doctoral researcher Xinyue Liu from the Massachusetts Institute of Technology (MIT) who reports a hydrogel that can adsorb more water at elevated temperatures. Liu and the research team from MIT and the University of Michigan were searching for a way to harvest water from the air without using a lot of energy. They want to tackle the problem of water scarcity and find a way of generating water sustainably. To do so, they tested many different sorbents. Most sorbents, such as zeolite and silica gel, have a structure that does not change much when it has adsorbed water; however, the polyethylene glycol – or PEG – hydrogel that the team synthesized is different. While it is semi-crystalline at 25°C, it becomes amorphous at 50°C. This structural change means that more adsorption sites are available at the higher temperature. As water is absorbed, it caused the hydrogel to swell, opening up further adsorption sites. The PEG hydrogel monomers are star-shaped, forming a network where the molecular weight can be precisely controlled. The shape of the monomer leads to very homogeneous structures, facilitating crystallization. The PEG hydrogel exhibited a water uptake of 0.050 grams per gram of polymer at 50°C and 50% relative humidity, with half this water uptake at 25°C and the same humidity. This work was published in a recent issue of Advanced Materials. 

Many industrial processes require heat or create it as a by-product. Now, Takayoshi Katase from the Tokyo Institute of Technology has found a way to harness this heat in an eco-friendly way, as he explains in an interview with MRS Bulletin podcaster Laura Leay. One way to harness this heat is to use thermoelectric devices to produce electricity via the Seebeck effect. Conventional thermoelectric materials, however, are composed of heavy metals such as lead and tellurium, which are toxic. To incorporate hydrogen into the structure, and so replace the toxic elements, Katase's research team used a rapid thermal sintering process where the starting material—which already includes the hydrogen—is sealed inside a tube. Some of the oxygen sites in strontium titanate are then substituted by the hydrogen. “More than expected, the hydrogen substitution reduces thermal conductivity less than half, and also increases electronic conductivity, resulting in the large enhancement of energy conversion efficiency,” Katase says. This work was published in a recent issue of Advanced Functional Materials. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Xuchen Wang of Karlsruhe Institute of Technology in Germany about his work on photonic time crystals. While conventional crystals are composed of repeating unit cells in space, such as eight carbon atoms arranged in a cube to form a diamond, a photonic time crystal has a structure that repeats in time. Theoretical predictions of photonic time crystals referred to designs consisting of three-dimensional metamaterials whose properties are difficult to manipulate in the laboratory. Wang and his collaborators have adapted the three-dimensional time crystal design to a two-dimensional metasurface. They arranged copper structures on the surface, using conventional printed circuit board technology. The structures look like a forest of mushrooms where the researchers placed a variable capacitor, known as a varactor, between each mushroom. To create the device, the researchers apply changing external voltages to the varactor, modulating the material's electromagnetic properties in time. Wang then confirmed experimentally that this device amplified microwave signals that he sent across its surface. This work was published in a recent issue of Science Advances. 

Little research has been done on the magnetic properties of high-entropy oxides, a challenge taken up by Alannah Hallas at the University of British Columbia in Canada, interviewed by MRS Bulletin podcaster Laura Leay. Hallas's research group began by choosing five elements that would be magnetic and combining them in oxide form, rendering a spinel structure for further experimentation. To understand how progressive substitution of the magnetic metal cations with non-magnetic gallium would affect the magnetic properties of the spinel, Hallas found that Ga substitution led to precise control of the configurational entropy, which may help to stabilize the spinel structure. Manganese, cobalt, and iron were redistributed throughout the structure whereas nickel and chromium were unaffected. Ga substitution led to the ability to tune the magnetic properties of the material in some unexpected ways that the research team calls “entropy engineering.” The ability to tune the properties may have applications for energy and data storage, for example, and could lead to more sustainable technologies. This work was published in a recent issue of the Journal of the American Chemical Society. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Widi Moestopo, a former graduate student in Julia Greer's laboratory at the California Institute of Technology (Caltech) and now a postdoc at Lawrence Livermore National Laboratory about their work incorporating microknots in architected materials. Using two-photon lithography, Moestopo scans a resin with a laser to create and shape a three-dimensional (3D) object within foam. Moestopo then used a solvent to wash away the remaining, unconverted resin. In this way, he sculpted the knots out of the resin, rather than tying the knots like shoelaces. This 3D structure is formed from a lattice of 3D rhombuses, where each side of the rhombus consists of three strands of fiber. These fibers are woven around each other to form knots. The result is a materials with high deformability and tensile toughness. This work was published in a recent issue of Science Advances. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Dominic Bresser from the Helmholtz Institute Ulm and the Karlsruhe Institute of Technology in Germany about the suitability of a nanotwinned copper foil as a current collector for the negative electrode in“zero excess” lithium−metal batteries. The nanotwinned copper foil has an essentially pure, single orientation and dense twin boundaries. Bresser's research group found that lithium deposits more densely and much more homogenously on this nanotwinned copper foil than on commercial foils. This work was published in a recent issue of ACS Applied Energy Materials. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Carmel Majidi from Carnegie Mellon University about an adaptive-responsive soft micro-robot. The key is eliciting a liquid–solid phase transition through electromagnetic induction. In addition to using the magnetic field to induce the phase change, it can also be used to make the machine move. A soft, low-rigidity body is vital for adapting a miniature machine to a variety of applications or a changing environment. This work was published in a recent issue of Matter. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Prof. Esma Ismailova and graduate student Marina Galliani from Mines Saint-Etienne about their work toward creating biocompatible, eco-friendly materials for wearable electronics. For this particular project, they developed a conducting material based on a commercial polymer known as PEDOT-PSS, in a water-based solution. They combined it with various solvents to tune the electrical conductivity, which is dependent on the shape and structure of the polymers in the material as they dry. The researchers tested the material's conductivity on several substrates, including paper-based substrates and textiles. To make the material printable, they also needed to tune the material's viscosity. Because the material relies on inkjet printers that are already commonly available, this material is relatively easy to incorporate into industrial processes. This work was published in a recent issue of APL Bioengineering. 

In this podcast episode, MRS Bulletin's Laura Leay interviews Rob Shepherd from Cornell University about an adaptive-responsive self-healing soft robotic system. Shepherd's research team has developed waveguides made of self-healing polyurethane urea crosslinked with aromatic sulfide bonds. When this material is cut, relatively weak hydrogen bonds quickly form. Disulfide exchange then occurs and, although this takes longer than the formation of hydrogen bonds, results in much stronger bonding and so recovering much of the mechanical strength of the polymer. Light is transmitted down the waveguide and, when the material is cut or punctured, the signal is attenuated. The loss of signal can be acted on by the robot and it can change its pattern of movement until the strong disulfide bonds are formed. This self-healing material absorbs more light than previous versions of the polymer that couldn't effect a chemical repair. This level of light absorption is actually useful as it makes the robot more sensitive to damage or deformation. This work was published in a recent issue of Science Advances. 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Jiahui Li, a graduate student at the University of Illinois Urbana-Champaign about designing structures out of gold nanoparticles. When the nanoparticle structure takes the shape of a pinwheel, different types of light interact with the structure differently due to its chirality. Different wavelengths might be transmitted depending on whether the light's polarization is rotating clockwise or counterclockwise, which could make this structure useful for filtering light in optical applications. This work was published in a recent issue of Nature (https://doi.org/10.1038/s41586-022-05384-8).

In this podcast episode, MRS Bulletin's Laura Leay interviews Robert Hovden from the University of Michigan and his graduate student Jonathan Schwartz on development of the freely available Tomviz platform (tomviz.org) that enables real-time three-dimensional (3D) visual analysis of materials. Building on the already existing Tomviz platform, Schwartz created new algorithms capable of pulling data from transmission and scanning electron microscopes, evolving the 3D image as the experiment progresses. This research is published in a recent issue of Nature Communications (https://doi.org/10.1038/s41467-022-32046-0). 

In this podcast episode, MRS Bulletin's Laura Leay interviews Tao Yang from the City University of Hong Kong in China who focuses on the innovative design of advanced structural materials. In the area of high-strength alloys, Yang's research team looked specifically at how to stabilize nanoparticles at high temperatures. In an alloy of Ni59.9-xCoxFe13-Cr15Al6Ti6B0.1, Yang's team achieved ultra-stable nanoparticles at 800–1000°C. They achieved this effect by tailoring the concentration of cobalt. While nanoparticles have already been seen to improve the strength of materials, Yang's team has provided insight into how this can be achieved at high temperatures. This research is published in a recent issue of Nature Communications (https://doi.org/10.1038/s41467-022-32620-6).

In this podcast episode, MRS Bulletin's Stephen Riffle interviews Alessandra Scagliarini, a professor of infectious disease at the University of Bologna, and Beatrice Fraboni, a professor of physics at the Department of Physics and Astronomy at the University of Bologna, about their electrical transistor assay that quantifies SARS-CoV-2 for antibodies. The purpose is to determine vaccine efficacy over time. The device is built with the semiconducting material poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The material not only transfers ion signals into electronic signals, but also amplifies it. Without neutralizing antibodies, the virus attacks the cells, causing both macro cracks as well as minor disruptions in the tight junctions of the cells, which the high sensitivity of this device is able to detect. This kind of data is an indirect way to assess whether patient samples have neutralizing antibodies. This work was published in a recent issue of Communications Materials (doi:10.1038/s43246-022-00226-6). 

In this podcast episode, MRS Bulletin's Sophia Chen interviews Murat Onen, a postdoctoral researcher at the Massachusetts Institute of Technology, about analog deep learning that could help lower the cost of training artificial intelligence (AI). The programmable analog device stores information in the same place where the information is processed. The resistor's main material is tungsten oxide, which can be reversibly doped with protons from an electrolyte material known as phosphosilicate glass, or PSG, layered on top of the tungsten oxide. Palladium is above the PSG layer, which is a reservoir for the protons when they are shuttled out of the tungsten oxide to make it more resistive. “When protons get in, it becomes more conductive. When the protons go out, it becomes less conductive,” says Onen. The resistance of this device responds in about 5 ns. This work was published in a recent issue of Science (doi:10.1126/science.abp8064).

In this podcast episode, MRS Bulletin's Laura Leay interviews Monica Olvera de la Cruz of Northwestern University and her colleagues who gained insight into biochirality. By analyzing self-assembly for a series of amphiphiles, Cn-K, consisting of an ionizable amino acid [lysine (K)] coupled to alkyl tails with n = 12, 14, or 16 carbons, the researchers found the degree of ionization is what controls the shape. They incorporate this phenomenon into a membrane energetics model. Furthermore, their experimental techniques show that the nanoscale structure of the chiral assemblies can be continuously controlled by solution ionic conditions. The model moves researchers one step closer to building entire cells in the laboratory and could lead to the development of nanotechnology such as drug delivery and electronics. This research is published in a recent issue of ACS Central Science (https://doi.org/10.1021/acscentsci.2c00447).

In this podcast episode, MRS Bulletin's Laura Leay interviews Sergey Artyukhin from the Istituto Italiano di Tecnologia and Louis Ponet, who is affiliated with both the Istituto Italiano di Tecnologia and Scuola Normale Superiore di Pisa about a topologically protected switching phenomena in ferroic materials. When a multiferroic crystal (GdMn2O5) is placed in a magnetic field at a very particular angle to a crystallographic axis, and the magnetic field is swept up and down twice, the system switches between four magnetic configurations. The interplay between the spin of the gadolinium and manganese ions leads to a unidirectional rotation of the spins and because this rotation is caused by the up-down sweep of the magnetic field, it can be thought of as a crankshaft. This four-state magnetoelectric switching emerges as a topologically protected boundary between different two-state switching regimes. While this magnetoelectric switching has only been observed in one multiferroic material, modelling can help predict other suitable materials from first principles. Eventually this could lead to new technology. This work was published in a recent issue of Nature (doi:10.1038/s41586-022-04851-6).