The question is always this: keep going with the materials that I am currently growing, or dedicate time to trying new materials. Its an age-old dilemma of not wanting to start over vs not wanting to be stuck on a path that less productive. In the world of 2D materials, this dilemma takes the form of sticking to the tried-and-true family of TMDC's (MoS2, MoSe2, WS2, WSE2), or to journey out into the uncharted waters of TMDC's where the metal is not M or W. It also means journeying out into the really uncharted waters of 3-6 and 4-6 binary 2D materials, such as SnS and GeSe. The prospect of growing these materials in large scale is tantalizing, if nothing other than for the prospect of having a complete library of 2D materials accessible at the wafer scale. I give much thanks to Yuda Zhao, who presented on PtS2, as well as for several others who presented on materials such as SnS. As a grower, I see small-scale proof-of-concepts as an encouraging sign that large-scale growth could be fruitful. After seeing the world of 2D materials on display here at MRS, I am encouraged that we will soon have access to them at the large scale, enabling a great variety of 2D devices to be made in the future.
Enough about science and talks, lets discuss food options. One of the food places I've frequented the past two days was Rice Paper (on Central and Monroe) for lunch, and the experience has been pretty good. It is Vietnamese Cuisine and has both restaurant area, a patio, and a small bar. Their menu ranges from Vietnamese sandwiches (banh mi), salads, pho noodles soups, and entrees (but they aren't available until after 4pm). Their service is pretty speedy and the food doesn't take too long to deliver to the table...which is perfect if you are in a rush to go back to the convention center to catch the next talk!
You can check their menu out here
*I was not sponsored or paid to make this post
Frontiers of Materials Research
Written by Lori A. Wilson
The National Academies of Sciences, Engineering, and Medicine held a town hall meeting on Wednesday to learn the perspective of members of MRS and where the materials community sees opportunities and gaps in materials research (MR), and to bring attention to a particular brand of research.
The Academies are assessing the progress and achievements in MR over the past decade. To help achieve this, they are seeking community input on the future of MR. Erik Svedberg, study director from the National Materials and Manufacturing Board, and Laura Greene, professor of physics at Florida State University, discussed how the Frontiers of Materials Research: A Decadal Survey looks at defining the frontiers of MR, ranging from traditional materials science and engineering to condensed-matter physics.
During the session, topics included achievements and principal changes in the research and development landscape; identification of key MR areas that have major scientific gaps or offer promising investment opportunities from 2020 to 2030; and challenges that MR may face over the next decade and how those challenges might be addressed.
This study was requested by the US Department of Energy and the National Science Foundation. The National Academies will issue a report in 2018 that will offer guidance to federal agencies that support materials research, science policymakers, and researchers in materials research, and other adjoining fields. Visit www.nas.edu/materials to learn more about the study.
Significant materials advances must be made over the coming decades
Written by Lori A. Wilson
Sabrina Sartori of the University of Oslo moderated a panel discussion on the materials needs for global energy sustainability by 2050. Topics included the fundamental materials research and development (R&D) that is necessary to achieve technical goals, geopolitical and international supply-chain implications of meeting necessary R&D challenges, and methods to achieve an energy-efficient, low-emissions future.
Panelists were Russell R. Chianelli of the University of Texas at El Paso, George Crabtree of the University of Illinois–Chicago and Argonne National Laboratory, Cherry Murray of Harvard University, and Ellen D. Williams of the University of Maryland.
Crabtree said the question that affects every material is why does it degrade? “How can we prevent it? We need to look at materials as they develop and see the failure as they operate. There’s no reason why a battery electrode couldn’t last 100 years if we could disrupt the degradation process,” he said.
Panelists addressed the need for research on how to lower the cost of batteries and a way of storing energy. Williams said that 60% of energy is lost in transmission lines. One way of helping to fix this is by using DC transmission lines.
The ability to achieve an energy-efficient, low-emissions future will depend on achieving significant materials advances over the coming decades, the panelists agreed.
This event was co-organized by MRS Energy & Sustainability—A Review Journal and the MRS Focus on Sustainability Subcommittee, with funding from the US National Science Foundation.
1st Place Winners
2nd Place Winners
Christianne M. Corbett, Stanford University
Solving the Equation: The Variables for Women’s Success in Engineering
As diverse as the population is in the United States, this diversity has yet to be represented in the fields of science, technology, engineering, and mathematics (STEM). In recent years, academia, government laboratories, and industry have identified the value of a diverse workforce and have done some education on explicit bias, for example, against women and underrepresented minorities; however, implicit bias—that is, indeliberate bias—still persists. At the Women in Materials Science & Engineering Breakfast, Christianne M. Corbett of Stanford University presented results of numerous studies conducted in more recent years to understand how implicit bias occurs. With acknowledgement of implicit bias, laboratories can then take action to change the research environment that will bring in more women and members of other underrepresented groups in order to strengthen their workforce. Read more about Corbett’s presentation, plus links to some of the studies, in MRS Meeting Scene blogger John Robertson’s report. This event was sponsored in part by MilliporeSigma (Sigma-Aldrich Materials Science).
Drop-Based Microfluidics—Applications for Materials and Biotech
Written by Don Monroe
Precise control of fluid handling and mixing using microchannels has become popular, for example for compact “lab on a chip” applications. In his Symposium X talk on Wednesday, David Weitz of Harvard University described a powerful version of microfluidics that exploits individual droplets, with applications in both specialty materials and tools for biotechnology.
“We use drops as a template around which we build new structures and try to create new and functional materials,” Weitz said. Under the right conditions, a steady jet of fluid from a microchannel breaks up into highly uniform droplets. Moreover, this process can be cascaded to controllably form drops within drops (and even within other drops) of chosen composition.
After developing the techniques by modifying standard lab capillaries, the researchers scaled it up to hundreds of photolithographically patterned channels in parallel. “This really starts to produce lots of material,” Weitz said, although he cautioned that it would likely remain economical only for high value-added products such as pharmaceuticals.
As an example that has lower regulatory barriers to entry, he cited cosmetics. In particular, he cofounded a company called Capsum that markets a lotion containing microdrops of oil, similar to the larger emulsions often used in cosmetics. Over nine months, the company used a benchtop device to produce a million units
A very different materials-production application, which has not yet attracted much commercial interest, is analogous to spray dryers that create small particles. About half of drugs are hydrophobic, Weitz said, and the resulting smaller particles have higher bioavailability.
When he and his colleagues adapted their microfluidic structure technique to entrain droplets in air, they were pleasantly surprised to find that the shear stress broke up the drops into much smaller particles of drug. Moreover, the cooling and concentration of the drug produced by the rapidly evaporating solvent resulted in spinodal decomposition and amorphous drug nanoparticles, which dissolve even faster than nanocrystals.
Weitz also described the powerful capabilities of drop-based microfluidics for lab-on-a-chip applications in biotechnology, which he said is “probably more important than making materials.” Studying reactions in individual drops with 10-micron diameters uses roughly 10,000,000 times less material than is required for a well in a 384-well microtiter plate, allowing vastly more experimental variants. “It is this decrease in size that’s one of the real driving features,” he said, including the reduced noise that goes with it. In contrast to standard microfluidics, moreover, the reactants in a drop do not touch the channel walls.
The technology that Weitz and his team develop includes drop makers that encapsulate singe cells, electrically-driven picoinjectors that inject reactants into individual drops, and sorters that separate out cell-containing drops that have specific optical signatures.
The researchers also used their technology to create hydrogel beads with unique genetic “barcodes.” Weitz co-founded a small startup to supply these labeled beads to other researchers.
In one powerful application, the team inserted barcoded beads into drops alongside single cells. Breaking the cells open within the drop lets the researchers create DNA sequences that splice together the barcode for an individual cell with the sequences that are being actively transcribed into RNA in that cell. Even when the DNA from many drops is later mixed together, the sequences can be traced back to a specific cell that can be tracked through its barcodes. Such single-cell RNA sequencing “can be done in wells,” Weitz said, “but drops are simpler and quicker.”
SPM Goes Live—Seeing Dynamic Phenomena with the Scanning Tunneling Microscope
Written by Arthur L. Robinson
“In order to break new ground in science, you have to build new machines” has been a guiding principle in Joost Frenken’s research career, a principle he took to heart as a graduate student in the early-1980s when Heinrich Rohrer and Gerd Binnig published accounts of their scanning tunneling microscope which led to his career of developing and using scanning probe microscopes to understand what happens on surfaces in real time under realistic operating conditions. In his Innovation in Materials Characterization Award presentation Wednesday evening, Frenken argued that to study phenomena like phase transitions and diffusion, one must develop instruments that are fast enough to follow atoms as they move around and that operate over a wide range of temperatures. For surface reactions, as in catalysis, operation under pressure is another requirement. Frenken proceeded to describe three specialized instruments developed by his group (and now commercialized by a spin-off company, Leiden Probe Microscopy) that have these capabilities and demonstrated their performance with examples.
The first instrument Frenken described was a variable-temperature, video STM with a temperature range from 50 K to 1300 K that can keep the same area of a sample surface in sight while scanning over a range of 300 K with a frame rate up to 25 frames/second. Applying this instrument to the motion of indium atoms on a copper (001) surface, the group discovered that the atoms covered a considerable distance in a single jump and that the jumps were assisted by a “mystery” particle that turned out to be a copper vacancy with a very high jump rate of 100 million jumps/second at room temperature. As a result, the copper surface is in constant motion (the surface is alive, he said). Investigations of other metal surfaces revealed similar behavior, suggesting this was a general phenomenon. The same instrument was later used in an in situ study of two-dimensional nucleation and growth of graphene films on a rhodium (111) surface exposed to very low (10–8 mbar) pressures of ethylene at 975 K.
For catalysis, theoretical phase diagrams of systems like palladium (100) exposed to carbon monoxide and oxygen show a variety of surface structures as the pressures of the gases change from miniscule to enormous values. Joost’s group developed their ReactorSTM to cope with this pressure range while also varying the temperature. The basic idea is that only a small area of one surface and the STM tip are exposed to flowing reactant gases, while the remainder plus standard sample-preparation and characterization tools, including an x-ray photoelectron spectrometer, are in UHV. The commercial version also incorporates an atomic force microscope. Frenken’s group studied several reactions with the instrument, including carbon monoxide oxidation, Fischer-Tropsch synthesis, nitric oxide oxidation and reduction, hydrodesulfurization, and chlorine production. For example in the Fischer-Tropsch synthesis reaction on a catalyst surface at 4 bar and 483 K , the group found that hydrocarbon molecules with 14 carbon atoms tended to fill the surface, but subsequent layers comprised much shorter molecules because the first layer acted like “molecular Teflon” for the next and it was harder to grow long molecules.
To conclude his talk, Frenken switched to investigations of the interface formation in multilayer mirrors for EUV-optics, a much-discussed next-generation technology for keeping the integrated-circuit industry on track to maintain Moore’s Law of doubling chip density every two years. Such mirrors may comprise 100 layers of alternating molybdenum and silicon that collectively promote Bragg reflection for the easily absorbed 13.5-nm EUV wavelengths intermediate between ultraviolet and soft x-rays. Roughness at the interfaces, however, degrades the reflectivity. To study the interfaces as they were growing, Joost’s group developed the Depo-STM with a tilt and rotation capability that allows individual atoms to land between the STM tip and the sample surface. To their surprise, when depositing molybdenum on silicon, they saw damage to the surface as silicon atoms were removed and MoSi2 clusters formed, creating a rough interfacial region containing the clusters. For silicon deposition, the effect is less pronounced. Frenken also described studies of surface erosion of silicon due to 800-eV argon ion bombardment.
Joost W.M. Frenken received the Innovation in Materials Characterization Award for the development, application, and commercialization of high-speed, temperature-controlled, in situ scanning probe microscopy, leading to key insights in the structure, dynamics, and chemistry of surfaces and interfaces. MRS acknowledges the generosity of Professors Gwo-Ching Wang and Toh-Ming Lu for endowing this award.