MRS Bulletin Materials News Podcast

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.