F.EN08: Scientific Basis for Nuclear Waste Management

Dennis Grödler, University of Cologne

Nanostructured Uranium Oxide Thin Films Developed by Molecular Precursors Using Chemical Vapor Deposition

Written by Emma Perry

UF6 is a waste product of the enrichment stage in nuclear fuel fabrication. It reacts with water to create hydrofluoric acid so it has to be managed very carefully. It is not profitable to convert UF6 into UO2 for nuclear fuel but perhaps it is for something else. For example, uranium dioxide is known to be a very good catalyst and to have semiconducting properties. In an experiment using alpha- Fe2O3 and U3O8 layers to enhance photoelectrical chemical properties of bare hematite, it was found that the heterojunction between U3O8 and Fe2O3 enhances the properties more than either layer separately. In order to create uranium oxide based catalysts and semiconductors it is necessary to make uranium oxide thin films.

Thin films can be made from chemical vapor deposition but first a precursor is needed that is stable in air, is volatile, is not toxic and has a defined decomposition.  Beta-ketonamines have been successful in the chemical vapor deposition of other compounds and can make a complex through simple salt metathesis. By experimenting with the ratios of reactants and catalysts it was possible to isolate a heteroleptic U(IV) complex. However, these were not volatile. Therefore a homeoleptic U(IV) complex was formed that is volatile and is stable in air.

F.MT03: Frontiers of Imaging and Spectroscopy in Electron Microscopy

Katherine Jungjohann, Sandia National Laboratories

Mapping Structure and Composition of Intact Li-Metal Anodes after Cycling

Written by Emma Perry

By using cryogenic focused ion beam and ultrashort pulse laser ablation it has been possible to observe the cross section of an intact lithium battery for the first time. A lithium coin cell battery is comprised of lithium, a separator, copper, and a liquid electrolyte. A solid-electrolyte interphase forms on top of the lithium. The characterization can distinguish between these regions and has proven to be extremely advantageous since the whole battery is involved in the processes that ultimately limit the lifetime of the battery. It is now thought that the solid electrolyte interphase disfiguration of the separators provides a pathway for lithium plating through the separator gradually reducing the amount of lithium in the electrode.

The wide range in length scales from 1 mm to 500 nm is what makes this technique so special. Katherine Jungjohann recommends intact characterization for understanding electrochemical variations in battery performance and invites users to apply the facilities at Sandia National Laboratories.

Symposium F.SM08: Regenerative Engineering and Synthetic Biology

Christopher Chen, Boston University

Engineering Vasculature Using Physical and Structural Cues

Written by Jessalyn Low Hui Ying

The establishment of perfusable vascular networks in three-dimensional tissue constructs is critical for the viability of cells and tissues in tissue engineering. In this talk, Christopher Chen presents his research team’s work on how physical and structural cues can be used to engineering such vascular networks.

Chen first explains that using a lab-on-a-chip model consisting of a cylindrical channel lined with endothelium, different growth factors and angiogenic factors can be introduced. This allowed the researchers to understand angiogenesis sprouting needed to form a capillary bed. As expected, it was observed that the rate of angiogenesis sprouting increases with decreasing matrix stiffness. Interestingly, however, if stiffness is too low, cells are scattered and a vascular network cannot be formed, attributed to decreased myosin activity.

With this understanding, the researchers then studied the capillary bed that forms after sprouting is completed. For this, they took inspiration from vasculogenesis – the process of vascular network formation during early development, and built a vasculogenesis-on-a-chip model. When endothelial cells were scattered in the gel, they were able to form an interconnected network, but were not perfusable. Perfusion of this network occurred only upon the addition of stromal fibroblasts. Chen explains that the presence of these fibroblasts, however, may cause fibrosis. Therefore, to engineer the removal of stromal fibroblasts, the researchers took inspiration from synthetic biology to add a split caspase construct. Upon dimerization, the caspase cascade is activated and apoptosis of stromal fibroblasts occurs. It was shown that with this process, fibroblasts were greatly reduced, but network remained intact and perfusion could still occur.

Chen then moved on to explain how this knowledge can be translated to achieving better perfused vascular networks in vivo. While the introduction of proangiogenic factors drives vascular network formation, the capillary bed is dense and disorganized, leading to a lack of perfusion and clotting off. Therefore, the researchers designed a pre-patterned network so as to guide incoming vascular networks and provide more structure. They found that by implanting endothelial networks built in vitro, the implanted structure gets interconnected with host vasculature and can be perfused. In fact, studies showed that when implanted into the ischemic zone of the heart, anastomosis between vasculature of well-perfused and ischemic areas occurred. Heart function was increased, further showing the potential of using these vascular network constructs to guide tissue formation and improve outcomes of tissue-engineered implants.

Symposium F.GI01: Special Symposium on Materials Approaches for Tackling COVID-19

Panelists: Burak Ozdoganlar, Carnegie Mellon University; Susan Daniel, Cornell University; Merlin Bruening, University of Notre Dame

Live Panel Discussion III: Fundamentals/Therapeutics

Written by Jessalyn Low Hui Ying

Three panelists presented key research contributing to therapeutic strategies for fighting the ongoing COVID-19 pandemic. While in different areas, one unifying factor is that their materials research projects were done during this pandemic and notably builds on the prior body of knowledge and research done in their respective research groups. In the live panel discussion of this session, besides addressing keynote-specific questions, much insightful discussion was raised on how COVID-19 has influenced the way research is done and public perception of science.

One key recurring idea in this panel discussion is how fighting COVID-19 is a multidisciplinary problem that requires much interdisciplinary collaboration between clinicians, biologists, materials engineers, computer scientists, and many other specialists. This is especially so as to achieve engineering solutions in a quick amount of time like in the case of pandemics, as well as to drive conversations and seek inspiration on how one’s expertise can be leveraged for achieving solutions for COVID-19. For example, Burak Ozdoganlar shared how their lab has been developing their microneedle array technology prior to COVID-19, but not for the delivery of vaccines. After building a collaboration with the Center for Vaccine Research at the University of Pittsburgh, conversation was generated on how their microneedle array technology can be used to deliver live attenuated viruses, which started the transition into research work for COVID-19. Susan Daniel also mentions how biology exhibits a strong structural-functional relationship and raises the possibility of using artificial intelligence to establish such relationships instead of achieving them empirically.

However, it is not only such scientific and technical collaborations that are important. Merlin Bruening points out that to realize the potentials of translational research, collaboration with industry and companies is essential to commercializing technology developed in academia. This is especially so to bring out technology rapidly, given the timescale of COVID-19. To this end, session co-chair Kaitlyn Sadtler highlights the importance of science communication to explain discipline-specific work to people from other fields, which also ties into public trust in science.

In fact, this pandemic has brought about many opportunities. COVID-19 has shown how researchers can be creative and adapt their research for advancing knowledge and technology in this pandemic, such as in therapeutics, diagnostic tools, and personal protective equipment. More importantly, researchers have built the body of work essential for preparedness for future pandemics, should this happen. Research and implementation, however, is a long-drawn preposition, as Ozdoganlar points out. He notes that for this, sustained good amounts of funding is critical for researchers to continue progressing with this work even when the COVID-19 pandemic subsides, to deliver something that is clinically relevant.

The panel discussion also raised insights on how COVID-19 has influenced the public perception of science and demonstrated how science is important in managing this pandemic. Bruening raises the fact that it is basic science and the fundamental discoveries in the past 20 years or so that has led to many scientific advances today like in therapeutics for tackling COVID-19. Besides this, Daniel also highlights how COVID-19 has drawn importance to the need for managing public health, other than personalized medicine which has been a huge focus pre-COVID-19. This underlies the fact that people and communities are deeply interconnected, leading to session co-chair Elizabeth Wayne pointing out, too, the importance of sociocultural dynamics in fighting COVID-19.

Kaitlyn Sadtler of the National Institutes of Health and Elizabeth Wayne of Carnegie Mellon University co-chaired this session, which can be viewed online through December 31st. Following are reports on each panelist prior to the discussion.

Burak Ozdoganlar, Carnegie Mellon University

Microneedles Arrays for Effective and Efficient Mass Vaccinations

An effective vaccination strategy, especially in the wake of COVID-19, should involve a potent vaccine and an efficient delivery system. Traditional vaccine delivery approaches via intramuscular or subcutaneous routes have many disadvantages, in particular requiring high doses. The skin, however, has a robust immune network that can be leveraged for vaccine delivery. In this talk, Burak Ozdoganlar presents an intradermal delivery strategy using dissolvable microneedle arrays (MNAs) developed by his research group.

MNAs involve hundreds of microsized needles fabricated in a patch form, and for dissolvable MNAs, these needles are formed from a mixture of dissolvable sugar-based material and biocargo. The fabrication of dissolvable MNAs involves a diamond micromilling process to achieve precise geometries and with high reproducibility. Upon insertion into the skin, the MNAs dissolve and deliver the biocargo into the skin, a process which takes only 10-15 minutes. These dissolvable MNAs for intradermal delivery of biologics host many advantages over traditional techniques (Mantoux technique), including being dose-sparing, reproducible, and pain-free. In vivo and ex vivo studies demonstrated the successful delivery of siRNAs and adeno-associated virus (AAV) vectors using this technology. Ozdoganlar mentions that there are, however, certain drawbacks that may affect the scalability of using dissolvable MNAs for clinical vaccination, in particular sterilization, which could affect the viability of vaccines; regulation challenges, whereby new FDA approval must be attained for each vaccine; and interference of dissolvable materials with presentation of vaccines.  

Ozdoganlar therefore next presents in his talk a novel next-generation system – hybrid MNAs. Here, the microneedle tips remain dissolvable, but cannulas are non-dissolvable. Instead, these cannulas connect to a reservoir of vaccines which allow for the continued delivery of vaccines from the backside upon dissolution of the tips when inserted. Having the vaccines in a reservoir provides many advantages, including being able to deliver any type of vaccine like live attenuated viruses, co-delivery of adjuvants, and non-influence of sterilization on vaccine bioactivity. In short, these hybrid MNAs retain all advantages yet addresses problems of dissolvable MNAs. This brings about immense potential for achieving a scalable and effective vaccine delivery system for global immunization programs.

Susan Daniel, Cornell University

Insight from the Physical Sciences on Coronavirus Host Entry and Therapeutic Interventions

For coronaviruses (CoV), the fusion of the virus and host cell membrane is mediated by the spike protein (S). Particularly, the fusion peptide (FP) within S interacts with the host cell membrane and plays a key role for viral genome transfer. Therefore, if the FP interaction with host membrane is inhibited, it may bring about significant advances in developing therapies against coronaviruses such as SARS-CoV-2, as in the case of COVID-19. In this talk, Susan Daniel presents her research team’s work on understanding the impact of calcium binding on CoV infection.

Daniel explains in this talk that the idea behind this was observing how the FP sequence is highly conserved across different coronavirus types like SARS-CoV and SARS-CoV-2, and in this sequence, runs of charged residues are present, which led the researchers to hypothesize whether calcium ions (Ca2+), which are fusiogens in other cellular processes, interact with charged residues of FP. In fact, cell infectivity studies using SARS-CoV showed that infectivity increased with Ca2+. To gain physical insight into this mechanism, various biophysical studies were done. Results showed that Ca2+ promotes the structural organization and alpha-helix stability of FP, which increases FP membrane insertion and lipid ordering of the host membrane. This is a precursor for membrane fusion to occur, associated with increased infectivity. In fact, isothermal calorimetry studies showed that Ca2+ interact directly with FP and knockout studies show that the charged residues of FP are indeed critical for calcium binding and infection.

With such knowledge that Ca increases CoV infection, the researchers tested if calcium channel blockers, typically used for treating cardiac disorders, can similarly limit SARS-CoV-2 infection. In vitro studies showed that some did successfully limit infection. Daniel explains that more studies are still needed, but these preliminary results indicate the potential for repurposing calcium channel blockers for the treatment of COVID-19.  

Merlin Bruening, University of Notre Dame

Membrane Based Affinity Capture to Quantify Antibodies to COVID-19

Antibody detection and quantification are essential for the management of viruses, especially in the case of pandemics where many clinical and public health decisions need to be made. In this talk, Merlin Bruening presents a porous membrane system that can be used to quantify antibodies which can be used for COVID-19.  

Bruening first explains the working principle behind this. These membranes are functionalized through a layer-by-layer deposition function to deposit polyacrylic acid (PAA) which contains carboxyl (COOH) groups. These can then be used to immobilize affinity molecules and consequently capture the antibodies of interest when serum is passed through the membrane. After rinsing, the elute can then be quantified to determine the antibody concentration. This is because when the researchers used a peptide mimotope to bind the monoclonal antibody Avastin, the elute was pure and showed high specificity. Fluorescence quantification of eluted Avastin gave a linear calibration curve and showed high recovery of Avastin, which indicates that this membrane-based affinity capture technique can be used for rapid absolute quantification of antibodies.

Bruening also further presents two different membrane-based designs that leverage on the same principle, but with a simpler design for antibody quantification. The first design is achieved via spotting the affinity molecules at the center of the membrane, then passing through fluorescence-labeled secondary antibodies after first passing through the serum with antibodies. In this way, the antibody concentration, which is proportional to fluorescence signal, can be analyzed directly from the membrane without a need for elution. The second design he talked about also uses fluorescence-labeled secondary antibodies, but this time, the entire 96-well plate is modified with the membrane at the bottom. In this way, no membrane holder is needed.

Bruening ends his talk showing how this membrane system can be used for the detection of monoclonal antibodies against COVID-19. To this end, they immobilized SARS-CoV-2 receptor-binding domain (RBD) proteins via amide bonds to the membrane and results showed that the absolute concentration of SARS-CoV-2 monoclonal antibodies could be quantified from conjugated fluorescence-labeled secondary antibodies. These studies highlight how this membrane system can enable rapid antibody quantification, even at the µg to ng/mL level.   

For more MRS Meeting Scene coverage of materials approaches for attacking COVID-19, see:

Personal protective equipment in the lab

Vaccination without injection – microneedle array skin patch to the rescue!

The role of calcium ions in coronavirus infection

Screening and Management of COVID-19 with Paper-Based Nanoparticle Tests

Towards the Design of a Novel Antimicrobial/Antiviral Filtration System

Plenary Session Featuring The Fred Kavli Distinguished Lectureship in Materials Science

Dario-gilDarío Gil, IBM T. J. Watson Research Center
Scaling the Scientific Method to Enter the Era of Accelerated Materials Discovery

“Right now is the most exciting time in computing in probably the last 60 years,” said Darío Gil, director of research at IBM T. J. Watson Research Center, “where we are witnessing the convergence of different ways to represent and process information.”

Gil is referring to the convergence of bits, neurons, and qubits enabled by the “cloud” programming environment with the help of artificial intelligence (AI) that changes the way problems can be solved. It is ushering us into the era of accelerated discovery. This is particularly critical for addressing global problems such as the current pandemic and climate change. 

To put this in perspective, Gil said the discovery of a new material—from the design concept to commercialization—takes about a decade, using capital of USD$10 million to USD$100 million. IBM wants to cut this effort by 90 percent.

Gil said, “We envision in the future inserting this technology [of quantum computing] to work in tandem with the AI-enriched simulation step of materials discovery loop.”

As our society is getting more and more digitalized, materials discovery in the field of semiconductors needs to accelerate significantly. IBM is aware that all of the materials going into computer chips must be as sustainable as possible. Gil focused his talk on the R&D of photoresists. Photoresists are a light-sensitive material used for forming semiconductor patterning.

Currently, photoresists carry potential toxic risks, so the research community needs to search for new photoacid generators (PAG). Gil showed step-by-step the advantages of using, first, the deep search method, which can complete complex queries on a photoacid generator—38 million edges (connections between entities or nodes that hold information that can also hold information)—in 0.1 s. This process led researchers to a PAG that was used for other applications but never tested for extreme ultra-violet (EUV) lithography.

AI-enriched simulation was then used to augment the material dataset with predicted properties. Generative modeling—a new capability in AI—accepted the information on materials properties and design constraints and filled in the gaps by generating 1000 PAG cation candidates with targeted properties. The next step is autonomous chemical synthesis in order to reduce trial and error and increase reliability and achieve scalability. This is where Cloud-based AI-driven autonomous laboratories become useful and IBM was able to show, on November 19, 2020, the first PAG material formed through this process.

Quantum computing works in tandem with AI, offering another revolution in discovery acceleration. A classical computer can be used for solving easy problems. However, for hard problems such as simulating materials, classical computers can provide only an approximation. “But there’s another technology that alters the equation between what’s possible to solve and what will be possible to solve,” said Gil, “and that is the world of quantum computers.”

IBM uses superconducting qubits, and has made its quantum computing accessible worldwide from the Cloud. In a nutshell, researchers write their programs which they send to the quantum computer that converts the 0s and 1s into microwave pulses that travel to the quantum processor. “We perform superposition, entanglement, and interference operations to perform the computation,” Gil said, then send the information back. Gil said that over 360 billion quantum circuits have been executed by quantum computers to date over the past four years with over 260k users. 

The Kavli Foundation is dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research and supporting scientists and their work.

Symposium F.EN08: Scientific Basis for Nuclear Waste Management

Daniel Gregg, Australian Nuclear S&T Org

Hot isostatic pressing of Synroc-C - the effect of Ti-metal additions

Written by Emma Perry

Daniel Gregg began this live session with a touching tribute to a valued member of this symposia for a number of decades, Eric ‘Lou’ Vance,

‘Although he was a world renowned scientist and authority on the development of waste forms for nuclear waste, Lou kept a relatively low profile, mainly because of his humble and unassuming nature but Lou’s career was absolutely stellar’

(see on demand talk F.EN.08.01.01). Many talks in the symposia drew on Lou’s work studying iodine incorporation into waste forms. In this talk Daniel Gregg updates us with the latest progress regarding Synroc-C, a material Lou Vance pioneered and continued to work on until he died in March last year.

Synroc is a multiphase ceramic composite waste form containing perovskite, hollandite, zircolite, and rutile designed to immobilize highly active waste produced in reprocessing spent nuclear fuel. The synroc durability can be increases by increasing the reducing the conditions in fabrication. It was hypothesized that titanium could facilitate this by absorbing oxygen.

In these experiments an ordinary synroc waste form is compared to those containing 4% and 8% titanium metal. When there is no titanium, Cs2MoO4 is observed to crystallize and dissolve in leaching tests. When 8% is added zirconolite and hollandite destabilize. But 4% titanium appears to be just right. At this percentage, there is no longer an interaction between the cannister and the waste form and the durability is greatly improved.

Symposium F.SM04: Degradable and Self-Healing Electronic Materials for Biological Interfaces

Carmel Majidi, Carnegie Mellon University

Pushing the Limits of Elasticity in Soft-Matter Electronics

Written by Jessalyn Low Hui Ying

Soft-matter electronics, used to interface with the human body, should be soft, elastic, and highly deformable, such that they remain electrically functional when stretched while returning to their natural length when unloaded. To achieve such soft electronic architectures, Carmel Majidi and his colleagues use liquid metallic alloys like eutectic gallium indium (EGaIn). This alloy has high conductivity and low viscosity; therefore, it can be incorporated into microfluidic channels to achieve highly stretchable circuity.

In Majidi’s laboratory, the soft-matter electronic circuits were achieved by patterning thin films of conductive poly(dimethylsiloxane) (cPDMS) with a deposited layer of liquid-phase EGaIn alloy using UV laser micromachining. The advantage of this method is that UV laser micromachining allows very fine circuit traces, down to 4.5 µm, making it optically transparent. When this circuit was bent and stretched, it still exhibited full digital circuit functionalities.

Microelectronic chips can then be incorporated into the laser-patterned liquid metal (LM) circuits. However, this has a problem of mechanical failure due to delamination between the microelectronic chips and surrounding soft materials. Therefore, another approach that Majidi’s lab has been taking more recently is to embed these liquid metal droplets into a soft polymer matrix, to form a liquid metal embedded elastomer (LMEE). Depending on the choice of polymer, the LMEE will exhibit different properties. This LMEE was demonstrated to exhibit many desirable properties - high elasticity, as metallic inclusions can be deformed together with the surrounding elastomer matrix, and enhanced fracture toughness, due to microstructure heterogeneity. LMEE could also support high elastic strain limits of above 600% strain while maintaining the electrical resistance. Using this architecture, the researchers also further demonstrated the fabrication of LM embedded polymer composites that exhibit electrically and mechanically self-healing properties, highlighting its potential uses for soft-matter electronics.

Symposium F.EN08: Scientific Basis for Nuclear Waste Management

Rebecca Lunn, University of Strathclyde

Development and Application of Colloidal Silica-based Grouts for Waste Containment

Written by Emma Perry

A radioactive leak in a Magnox Swarf Silo presents an interesting materials problem.

In this talk Rebecca Lunn shows us how her colloidal silica-based grout could save the day. Injected from outside of the silo, the viscosity of these grouts can be controlled with the correct dose of electrolyte accelerator. This way the grouts are viscous enough to flow into a crack and then they set at just the right time to seal it. Modeling of the injection and setting has been verified with tank injection tests.

It is important that the grouting is durable and that it will not mobilize radionuclides in the surrounding concrete and soil. Sorption experiments have shown that grouting causes a net increase in adsorption by providing a large amount of silica surface area for outer sphere Sr and Cs surface complexation.

Symposium F.SM05: Brain-Inspired Information Processing—From Novel Material Concepts for Neuromorphic Computing to Sensing, Manipulation and Local Processing of Biological Signals

Charles Collier, Oak Ridge National Laboratory

Memory and Learning in Biomolecular Soft Materials

Written by Jessalyn Low Hui Ying

Neuromorphic elements to mimic sensory neural pathways traditionally use solid-state devices. However, this has key differences from the natural sensory nervous system, in particular that the brain is not a solid-state device and that communication is ionic, not electronic. In this talk, Charles Collier presents about how his research laboratory develops lipid and polymer bilayer based synaptic mimics that connects pre- and post-synaptic neurons. “Lipid bilayer membranes mimic the architecture, mechanism and functionalities of natural synaptic functions,” says Collier.

To form these lipid bilayer membrane structures, a droplet interface bilayer (DIB) method is used, which is based on the self-assembly of lipids at the oil/water interface. When the droplets come into contact, they form interfacial bilayers that mimic that in cell membranes. It was demonstrated that when doped with alamethicin, a voltage-dependent pore-forming peptide, the DIB system is able to exhibit memristive and memcapacitive behaviors. Collier also mentions that the DIB system exhibits short-term synaptic plasticity (STP) in conductance, which is important for cellular communication, like in paired-pulse facilitation (PPF) and paired pulse depression (PPD). STP also supports signal processing functionalities like frequency filtering and gain control. This is unlike in solid-state devices which exhibit long-term synaptic plasticity. Collier further highlights that these lipid bilayer membranes are memory capacitors whereby capacitance is not a constant. The mechanism behind this is electrostriction, a phenomenon that includes electrowetting and electrocompression. In the presence of an electric field and voltage changes, structural changes particularly membrane area and thickness cause a build-up of charge in the membrane.

Besides lipid bilayer membrane structures for synaptic mimics, the research team also researches into polymer bilayer structures, which will provide the additional ability for control into properties like amphiphilicity and charge. In this polymer bilayer structure, reversible voltage-activated thresholds were needed for membrane formation. This means that bilayers were formed spontaneously at low ionicities, but at high ionicities, applied voltage is needed to provide an electrocompressive stress that overcomes repulsive disjoining pressures between droplets to form the bilayer. This switching of assembly behavior can also be used as a mechanism for short-term synaptic plasticity.

Symposium F.MT03—Frontiers of Imaging and Spectroscopy in Electron Microscopy

Charudatta Phatak, Argonne national laboratory

Frontiers in imaging functional behavior in nanoscale heterostructures using Lorentz transmission electron microscopy

Written by Emma Perry

When using TEM out of focus on a sample it is possible to see bright and dark lines that show changes in magnetic field lines indicating the presence of domain walls, vortices, or skyrmions.

By recovering the phase shift of the electron wave it is then possible to separate the contribution of the electrostatic and magnetic contributions to the phase shift. In this talk Charudatta Phatak presents how to make a map of integrated magnetic induction and links to their python GUI to help you do it (https://github.com/PyLorentz/PyLorentz). The group’s most recent work is focussing on the use of neural networks to reconstruct phase at a high spatial resolution.

The talk concludes with a study of Neel-type skyrmions created by Ga ion implantation of Pt/Co thin films. Using the described techniques the magnetic spin textures were visualized. By observing the skyrmions as a function of time it was possible to see them grow to a critical size before annihilation.

The live talk includes bonus material featuring the dependence of three-dimensional CO nanohelics curvature on dwell time and electron accelerator voltage as well as the behavior of neeltype skyrmions induced on thin Fe3GeTe2 layers as the temperature is lowered through the Curie temperature.