Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Elisabeth Bik, Harbers Bik LLC

The Dark Side of Science: Misconduct in Biomedical Research

Written by Alison Hatt

In her Symposium X presentation, Elisabeth Bik talked about her efforts to identify and address misconduct in the scientific literature. “Science should be self-correcting,” she said, “and I try to be part of that process, because that’s going to make science better.” 

Science misconduct can take the form of plagiarism, falsification, or fabrication of data. Much of Bik’s work has focused on inappropriate image duplication, in which authors use the same image or data set multiple times to represent different experiments or results, often altering or repositioning elements using image-editing software. While most of her work is focused on the biomedical field, Bik showed several concerning examples from materials science publications where, for example, the same x-ray diffraction pattern appeared to be used to represent different materials compositions or a micrograph was clearly a composite image of the same few nanoparticles repeated over and over again.

Bik shared results of a study where she scanned more than 20,000 biomedical papers by eye and identified duplicated images in 4% of them, about half of which appeared to be cases of misconduct. Disappointingly, reporting these papers to the journals in which they appear does little to solve the problem. Of hundreds of papers Bik has reported, only about a third get retracted or corrected, and in most cases the journal takes no action. And even when journals do act, they tend to do so slowly, often allowing fraudulent papers to remain in the scientific literature for five or more years in the meantime.

Disillusioned by this response, Bik now posts her concerns to the website PubPeer.com rather than reporting to the individual journals. She encouraged the audience to install the freely available PubPeer extension that identifies papers that have received comments from the community, so researchers can avoid building their own work on problematic data.

The individual researchers who commit misconduct are typically driven by desperate situations, Bik noted, saying that behind every misconduct case is a sad story. Researchers may be subject to unrealistic requirements or expectations of their employers, or they could be junior researchers working under a bullying professor who demands results. Bik is more critical of the journals that allow papers to pass through peer review without apparent scrutiny and institutions that impose strict mandates on the number of publications needed for career advancement.

Bik is also critical of papermills that sell fake articles written by ghostwriters using fabricated data. She showed an example of an identical data set appearing in several very different papers. Another approach used by papermills is synonymized plagiarism, in which an article is copied verbatim but every word or phrase is replaced by a synonym, resulting in bizarre but comprehensible prose.

The rise of advanced computing and artificial intelligence complicates matters. Computer programs can more rigorously scour publications to identify duplicated images and problematic data, but their results are prone to false positives and need to be validated by humans. Meanwhile, AI is getting increasingly good at creating fake pictures and will almost certainly be capable of generating images for research articles that won’t be easily detected by journals or reviewers.

Bik presented several measures to help prevent misconduct in scientific literature. We should continue the trend toward open science, where researchers share full data sets and not just the snippets that appear in articles. Culturally, we should reduce our emphasis on publications as measures of research productivity and focus on mentoring students and junior researchers in good research methods. Reports of misconduct should be resolved quickly by journals and not allowed to remain in the literature, and strong consequences should be imposed on those who commit misconduct. Journals should also take greater responsibility for checking the papers they publish. Finally, the people who report misconduct need to be protected from retaliation, as the work is a necessary part of the self-correcting scientific process. 

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

Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Xinliang Feng, Technische Universität Dresden

Advances in Organic 2D Crystals—From On-Water Surface Chemistry to Functional Applications.

Written by Vineeth Venugopal

In his Symposium X presentation,  Xinliang Feng of the Technische Universität Dresden spoke about inorganic two-dimensional (2D) crystals such as dichalcogenides, boron nitride, black phosphorus, metal oxides, and nitrides beyond graphene. He noted that there has been much less development in organic 2D crystalline materials, including the bottom-up organic/polymer synthesis of graphene nanoribbons, 2D metalorganic frameworks, and 2D polymers/supramolecular polymers, as well as the supramolecular approach to 2D organic nanostructures. 

Organic two-dimensional soft matter are 2D nanostructures that can be easily deformed by thermal stresses or thermal fluctuations at about room temperature. They include graphene oxide, 2D supramolecular organic nanoarchitectures, from surface synthesis, amphiphile, colloids, biomembrane, and liquid crystal. Organic 2D materials can include synthetic graphene, 2D polymers/supramolecular polymers, single/ few layer 2D COFs/MOFs, and crystalline polymer nanosheets, for example. These have applications, for example, in energy storage, photo/electro catalysis, sensors, superconductivity, topological insulators, and spintronics. 

Recently, Feng’s research group observed fractional edge excitations in nanographene spin chains. This has led to work on G-nanostructures and organic 2D materials such as 2D polymers and conjugated polymers. 

One of the central chemical challenges is to realize a controlled polymerization in two distinct dimensions under thermodynamic/kinetic control in solution and at the surface/interface. In this talk, Feng presented his group’s recent efforts in bottom-up synthetic approaches toward novel organic 2D crystals with structural control at the atomic/molecular level. On-water surface synthesis provides a powerful synthetic platform by exploiting surface confinement and enhanced chemical reactivity and selectivity. 

Feng presented a surfactant-monolayer-assisted interfacial synthesis (SMAIS) method that is highly efficient to promote programmable assembly of precursor monomers on the water surface and subsequent 2D polymerization in a controlled manner. Two-dimensional conjugated polymers and coordination polymers belong to such materials classes. The unique 2D crystal structures with possible tailoring of conjugated building blocks and conjugation lengths, tunable pore sizes and thicknesses, as well as impressive electronic structures, make them highly promising for a range of applications in electronics, optoelectronics, and spintronics. Other physicochemical phenomena and application potential of organic 2D crystals, such as in membranes, were also discussed.

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

Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Suman Datta, Georgia Institute of Technology

Plenty of Room at the Top and Bottom

Written by Alison Hatt

In Thursday’s Symposium X symposium, Suman Datta took the audience through two decades of his work on transistor technologies and highlighted some formidable challenges currently on the horizon. His talk was titled, “Plenty of room at the top and bottom,” and he stressed that early-career scientists entering the field today will still find ample research opportunities for decades to come. “No matter what you hear in the press about things coming to an end,” he said, “the semiconductor industry is actually pretty healthy.”

When Datta’s career was starting in the early 2000s, the semiconductor industry was in the era of “geometric scaling,” continually reducing the dimensions and operating voltages of transistors in order to improve performance and fit ever more transistors on a chip. In his early work at Intel, Datta and colleagues brought transistor dimensions down almost to single-digit nanometer scales, developing a 10 nm silicon transistor using spacer lithography. The device pushed the boundary of what was possible at the time but had major technological problems, including direct tunneling of current through the very thin gate oxide, which meant the transistor effectively couldn’t be shut off.

The team (and the broader field) realized they needed to find other ways to scale the technology and started pursuing new approaches to improving transistor performance, resulting in three key innovations. First they developed innovative ways to introduce strain into the transistors to change the effective mobility and velocity of carriers in the channel. Next they replaced the silicon dioxide with high-k transition metal oxides to overcome reductions in mobility caused by phonon scattering. Finally they changed the planar transistor geometry to a non-planar configuration, referred to as tri-gate or FinFET.

As he described each of these innovations, Datta noted a recurring theme whereby the solution to one challenge would often bring other unexpected benefits through a kind of technological serendipity.

Today the industry is in a mode Datta described as “hyper scaling,” where dimensions of transistors are on the order of Angstroms. He described efforts needed to fabricate the increasingly complex geometries involved and the challenges of thermal management when delivering power to billions of transistors in a single chip.

While advances in transistor performance continue to grow our logic capabilities, Datta noted that we’re now coming up against a memory bottleneck. Conventional computers make data locally available to logic cores by moving it from off-chip DRAM into a local cache (SRAM) that can be accessed with very high internal bandwidth. However, applications like training neural networks require enormous amounts of data that can’t fit in a local cache, creating a bottleneck in how fast the data can be accessed on off-chip memory. Datta discussed his work developing embedded on-chip DRAM, stacking up cache memory directly on the chip instead, which comes with a plethora of technological challenges. He also discussed efforts to reduce data-shuttling needs by performing some logic in the memory itself, again highlighting areas rich with research challenges for young researchers.

Datta identified a list of needs to maintain compute performance gains in the coming decades: accelerated development of materials with tailored properties; monolithic three-dimensional technologies for logic, memory, power delivery, and thermal management; design automation to help assemble mix-and-match technologies; and co-optimization of devices, circuits, systems, and applications for maximal use of hardware resources.

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

Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Jennifer A. Hollingsworth, Los Alamos National Laboratory

From Flask to Devices—The Making of Exceptionally Functional Colloidal Quantum Dot Emitters

Written by Don Monroe

In her Symposium X talk, Jennifer Hollingsworth discussed designing and making nanocrystal quantum dots that could potentially address the demanding requirements of quantum information technology.

The optical transitions in semiconducting quantum dots are shifted to higher energies by quantum confinement of their electrons and holes. Their optical properties can therefore be tuned by changing their size, typically a few nanometers in diameter. Colloidal synthesis techniques, such as successive ionic layer adsorption and reaction (SILAR) provide “angstrom-level control over size,” notably for CdSe. Quantum dots have many applications involving photon conversion, emission, and photocarrier generation.

For quantum computing, defect states like the “NV” center in diamond feature coupled spin and visible-light degrees of freedom that could be useful for quantum information processing. Hollingsworth asked whether an “artificial NV center” might be made through chemistry, with the spin degree of freedom of a metal-containing molecule coupled to the polarized emission of a separately optimized quantum dot. The strict requirements for the quantum dot are challenging however, including on-demand, tunable emission of near-infrared “telecom” wavelengths with high purity, brightness, and directionality. The devices will also need to be integrated with devices, and indistinguishability of the photons is “probably the most challenging factor that we face,” Hollingsworth said.

CdSe nanoparticles coated with a thin CdS shell historically had problems with “blinking” (going dark and recovering) and “bleaching” (getting progressively dimmer). Hollingsworth attributed these issues to two mechanisms: non-radiative Auger recombination that imparts the energy to a nearby electron instead of a photon and trapping of photoexcited carriers in surface states. More than a decade ago, she and others dramatically reduced these effects using thick CdS shells, 15-20 nm in thickness, to make “giant quantum dots.”

A second important design tool is the band offsets between the core and shell. “Type I” offsets confine both the electrons and holes to the core, while “Type II” only confines one carrier. A related approach uses a graded transition between core and shell rather than an abrupt one. With these new design parameters, Hollingsworth and her colleagues have explored an entire family of giant quantum dots. The improved stability opened a range of applications, such as long-term single-molecule tracking.

She also studied the differences between the “very tedious” monolayer-by-monolayer SILAR method and an alternate “continuous injection” method. Although both methods avoid blinking and bleaching, there are other important differences, where she traced different numbers of stacking fault, chemical terminations, and alloying. An even better hybrid method starts with SILAR but ends with continuous injection and a long anneal. “We have achieved on-demand single-photon sources,” Hollingsworth said.

CdSe quantum dots are limited to the visible, but giant quantum dots with a PbS core emit at room temperature in the near-infrared telecom bands around 1.3 micron and 1.5 micron, which is desirable for optically transmitting quantum information.

Hollingsworth also described advances in the brightness toward the roughly 10⁹ photons per second needed for quantum information. One approach exploits the localized surface plasmon resonance of a nearby conductive particle to enhance the spontaneous emission rates. However, the popular noble-metal particles do not support these resonances in the infrared, so researchers are looking at other materials, including tunably doped semiconductors and the spinel magnetite_.

Unfortunately, this plasmonic technique enhances the nonradiative rates as well as the radiative rates, Hollingsworth said. To enhance only the radiative rate, she collaborated with Maiken Mikkelsen’s group at Duke University to couple quantum dots to nanopatch antennas, reducing the radiative lifetime from microseconds to nanoseconds—yielding nearly a thousandfold brightness increase—or even shorter.

She also collaborated with Ronen Rapaport of the Hebrew University of Jerusalem, using dip-pen lithography to place quantum dots in the center of a bullseye antenna. These techniques enhance the brightness and produce directed emission that enhances collection efficiencies.

Hollingsworth sees paths forward in achieving better photon purity and device integration. To achieve the longer-term challenge of indistinguishable photons, she said, “we need to combine strategies of synthesis and integration.”

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

Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Jian Cao, Northwestern University

Physics-based AI-assisted Property Control in Metal Additive Manufacturing

Written by Sophia Chen

During Tuesday’s Symposium X, mechanical engineer Jian Cao of Northwestern University described research efforts to incorporate machine learning and simulation to improve the technology’s consistency in a talk titled “Physics-based AI-assisted Property Control in Metal Additive Manufacturing.”

In metal additive manufacturing, machines build a metal component layer by layer out of metallic powder or wire and fuse the layers using heat from lasers, electron beams, or other sources. The technology, popularly known as metal 3D printing, dates back to the 1990s, when engineers first used the 3D printed components for rapid prototyping and testing.

Today, engineers use the technology to create components for aerospace, biomedical, and automobile applications. In the last decade or so, metal 3D printing has begun to play a role in final production. However, scalability poses an issue, as the printed components lack consistency. One prototype may have vastly different mechanical properties than another ostensibly identical component.

Cao’s group studies how machine learning and physics simulations could help the metal additive manufacturing process be more consistent. Her talk centered on “how mechanics and AI work together for manufacturing process, design, modeling, and control,” she said. The physics and AI-based modeling predicts how the powder or wire melts and cools, which in turn determines the component’s mechanical properties. Based on those predictions, the researchers can adjust the manufacturing process to achieve the mechanical properties they want.

For example, Cao’s group recently devised a process that used both machine learning and physics to reduce the number of holes that form between metal layer. The holes constitute an undesirable property known as porosity that weakens the material. One way to control the material’s porosity is to make the melt pool—the area of the component that the laser melts—as consistently as possible.

The physics-based strategy involved numerically simulating the melt pool. Porosity is related to the geometry of the melt pool, Cao explained. To accurately simulate melt pools, the researchers first conducted high-speed x-ray imaging of the 3D printing process at the Advanced Photon Source at Argonne National Laboratory in Illinois. Specifically, they studied a metal 3D printing process known as directed energy deposition. In their setup, focused heat from a laser melts metal powder.

Cao’s team studied how the laser scanning speed, the rate of deposition, among other variables, affected the printed component’s porosity. To study these variables more efficiently, they developed a high-throughput setup that could easily adjust the parameters of the 3D printing process. Using these x-ray images, they characterized the geometry of the melt pool and the pores that formed. In addition, they simulated the depth of the melt pool. The researchers found that by controlling the laser’s intensity, they could produce a melt pool with more consistent depth, and thus control the porosity.

They then took samples out of the materials produced in this process and correlated the material’s mechanical properties with how it cooled, also known as its thermal history. This was the AI part of the process, as they used a purely data-driven algorithm known as a random forest without incorporating any physics knowledge. Using this information, the researchers created a type of AI model called a neural network which they combined with a physics model that could control the material’s thermal history.

In the future, the field needs to work on bridging designers with manufacturers, said Cao.  In particular, she highlighted the need for databases between the two groups. “Materials science has been doing pretty well to generate common databases,” she said. “On the manufacturing side, not really. This is something that we need to catch up.”

In addition, the field needs to continue developing new techniques to measure and characterize the process, an area Cao refers to as functional metrology. They need new ways of determining what kinds of flaws are permissible, beyond studying the melt pool geometry and the texture of the surface.

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

Symposium X—MRS/The Kavli Foundation Frontiers of Materials

Xiaoqing Pan, University of California, Irvine

Probing the emergent properties and dynamics of interfaces by electron microscopy

Written by Vineeth Venugopal

In his Symposium X presentation, Xiaoqing Pan of the University of California, Irvine, talked about his extensive research on the study of functional materials systems using the electron microscope. The electron microscope as a characterization tool has undergone rapid development in the last two decades with specialized aberration correction devices approaching sub-angstrom resolutions. It is being used to study the dynamic behavior of materials, their electronic properties, and phonon characteristics, among other modalities. 

Pan spoke at length about his work on using the electron microscope to study the properties of ferroelectric devices. “Ferroelectrics are materials with spontaneous polarization,” he said. A good example is bismuth ferrite or BiFeO₃, which, like all ferroelectrics, has multiple microscopic regions of polarization called domains. The polarization in each domain is in the same direction but that of adjacent domains can be at an angle to each other. In the case of BiFeO₃, adjacent domains can be at 71, 180, or 109 degrees and they appear as neatly demarcated stripes in a microscopic image. The surfaces of these domains attract charge which is retained as the so-called “bound charge.” Different functionalities of the electron microscope have been used to extract complementary information about ferroelectric domains and thus have helped in our understanding of the origin of ferroelectricity. 

Using the electron microscope, Pan and his colleagues have been able to measure ferroelectric polarization and map its spatial distribution with atomic resolution. This has allowed correlating the dipole moment of BiFeO₃ with the real time atomic displacements of oxygen in the material. They have also been able to probe the dynamics of domain nucleation and polarization switching at the atomic scale as well as to image the local charge density in real space. This has led to the real time observation of the pinning of ferroelectric domains at dislocations in the crystal lattice.

In other systems such as strontium titanate, the electron microscope has revealed the surface is conductive at microscopic scales even though there is no overall macroscopic conduction. By using charge density imaging techniques, the momentum space can be mapped by an electron probe which shows the presence of polarization vortices in several of these materials due to local heterogeneity and bound charges. The probe in a four-dimensional scanning transmission electron microscope interacts with the local charge directly which enables the quantitative analysis of charge transport and local dipole moment. 

In addition, Pan has used the electron microscope to study long and medium wave phonons in the crystal system which is useful in the study of thermal conductivity of materials. In SiGe quantum dot superlattices, the electron beam has been used as a source of phonon that can be used to study the stepwell phonon emission spectra. He pointed out that a more stable low temperature sample holder will be very useful for the future of electron microscopy studies by allowing far more measurements than we are able to do today. 

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

Plenary & Featured Talks available online through June 30, 2022

Today is the last day of the 2022 MRS Spring Meeting & Exhibit. A great benefit of the hybrid design is that some of the talks are available on the virtual platform through June 30, 2022. This includes the Plenary and Featured Talks - which means all of the presentations given in Symposium X: Frontiers of Materials Research!

As a preview to the Symposium X speakers, here are two of the interviews done with MRS-TV.

"From Atom to System—Tera-Scale Energy Transition with Better Batteries” – Symposium X speaker Y. Shirley Meng

 

The Light Stuff: Enabling Sustainable, Product-Selective Photocatalysts with Plasmonics – Symposium X speaker Jennifer Dionne of Stanford University

Blogger: Judy Meiksin

The Rise of 2D Halide Perovskites – Symposium X speaker Aditya Mohite of Rice University

Two-dimensional halide perovskites (2D-HaP) are a sub-class of 3D perovskites, which have emerged as a new class of solution-processed organic-inorganic (hybrid) low-dimensional semiconductors. 2022 MRS Spring Meeting Symposium X speaker Aditya Mohite discusses his work on 2D-HaPs ranging from the fundamental light-induced structural behaviors, and solvation dynamics to control homogeneity of layer thickness, novel photo-physical behaviors, charge transport and their role in a high-efficiency optoelectronic device, with technologically relevant durability. Mohite's presentation can be viewed online through June 30, 2022.

 

 

Symposium X—Frontiers of Materials Research

Benjamin C.K. Tee, National University of Singapore

AI Skins for Good

Written by Don Monroe

In his Symposium X presentation, Benjamin C.K. Tee of the National University of Singapore discussed applications of sensor devices that use soft materials, including electromechanical sensors, self-healing devices, stretchable electronics, and neuro-inspired devices.

The widespread adoption of artificial intelligence (AI) is driven by the recent explosion in the amount of data available, much of which comes from sensors, Tee said. Thus, making sensors more ubiquitous, versatile, and robust can provide data for an even wider range of applications for the benefit of humankind.

Materials science and engineering are critical for enabling these novel devices, and there have been many good devices and systems proposed, Tee said. The resulting electronic skin integrates and processes many sensory inputs in parallel,” he noted. He emphasized the importance of a multi-disciplinary approach that extends beyond device design to include a systems perspective, including AI and even biological science.

The human sense of touch augments vision for many tasks, such as manipulating objects and navigating the world. Skin-like structures incorporating force-sensitive devices could therefore be very powerful in robotics, for example grasping delicate items, and, Tee said, perhaps other applications that we haven’t thought of yet. In one example, he described a heads-up display for a surgeon (or trainee) that tracks in real time the forces on a scalpel from healthy or tumor tissue.

Traditional electronic materials have stiffnesses of many gigapascals, much greater than that of skin, which is of order megapascals, or of tissues such as brains, below a kilopascal. “One of the biggest challenges to developing soft, flexible materials that can perform functions is the ability of human skin to maintain functionality and robustness despite mechanical strain,” Tee said. “Generally, you can stretch 10–15%.”

He showed one enabling technology in which helical metal wires embedded in elastomer suffer no change in conductivity even with very large strain. His team has developed a platform that accurately predicts the behavior of well-characterized materials in novel devices.

Unfortunately, soft materials tend to be viscoelastic, resulting in large hysteresis in force sensing. Although machine learning can partially compensate for this behavior, Tee said, “Despite the best AI, you need good sensors to get good accuracy,” as illustrated by an improved, almost hysteresis-free device his team developed.

Large-area electronic-skin systems also struggle to convey the information from many sensors. “It can be quite impractical to do this with normal wires,” Tee said. To address this issue, his team developed ACES, or asynchronous coded E-skins, which multiplexes the outputs of many sensors, with orders of magnitude faster response times—almost 10 megahertz instead of around a kilohertz. “Such systems might make it more scalable,” Tee noted.

Another powerful communication strategy is the use of action potentials like those used in human brains. This biology-inspired strategy allows more efficient transmission of sensory data. Indeed, companies including Intel have developed “neuromorphic” chips that perform powerful computations with much less power than traditional graphics processing units.

Large arrays of sensors also need to be robust against failures of individual devices. Tee showed an example system design that has multiple wires for each device to provide redundancy, as well as reconfigurability.

At the device level of robustness, he described research on self-healing materials, which can repair themselves even under water. In addition to being more convenient, such long-lived devices could reduce the significant environmental impact of electronic waste.

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

AI Skins for Good – MRS Symposium X Speaker Benjamin C.K. Tee

Benjamin C.K. Tee of the National University of Singapore discusses his group’s materials design and strain optimization techniques to develop electronic materials with stretchability, sensitivity and self-healing properties. Such materials and technologies can be tremendously useful in distributed conformable electronic skins, neuro-prosthetic devices and robots in the increasingly digitally augmented future for the benefit of humankind. Tee's talk is scheduled for May 24, 8:00 am (EDT).