Symposium BI02—Women in Materials Science—Pioneers and a Vision for a More Inclusive Future

I am a Professor of Mat Sci, Mechanics, and Medical Engineering at Caltech, and apparently I am a bad scientist. At least that’s what my advisor told me when I was a Master’s student at Stanford. Is there anything you are bad at? Because it turns out that sometimes being told that you are bad at something can make you excel at that very thing. I finished my Ph.D. degree at Stanford and spent a couple of years working at Intel, after which I had decided that if I were a bad scientist, at the very least I should be one with a Ph.D. I was lucky enough to become a Ph.D. student at Stanford in a research group of Prof. William D. Nix, affectionately known as “the Boss.” At that time, Stanford's Materials Science department did not have a single woman faculty member.
Together with the Boss we discovered that tiny little crystals of common metals – like gold, copper, and nickel, which we know to be quite malleable – become exceptionally strong when their dimensions are reduced to ~ 200nm, or ~1000^th of your hair diameter. We coined this phenomenon a “smaller is stronger” size effect. Working with Bill Nix had a tremendous impact on my life; to this day, he is quite possibly the most influential person in my professional career – he saw me transform from being a young “bad scientist” into a decent thinker. Most importantly, he believed in me, as he did in all of his graduate students, many of whom were women. And we rose to the occasion.
At the end of my third year in graduate school, I did everything backwards: I first had two faculty interviews for professorships at Caltech and MIT, I then interviewed for a post-doc, and finally defended my Ph.D. dissertation on May 16, 2005.
I built my professorial career at Caltech in Materials Science "option" (in the Division of Engineering and Applied Sciences) to study all things nano (materials and architectures) – much because of our discovery during my Ph.D. that materials behave differently at nano-scale. In the back of my mind, I had always wondered if there was a way to somehow harness these unique properties offered by nanomaterials and proliferate them onto larger scale so that we can have materials that behave as though they were nanomaterials but they look like our regular, macroscopic objects.
Fast forward a decade – I am now an endowed, chaired professor at Caltech, having accumulated multiple national and international recognitions and awards. I run a research group with 20+ incredibly smart, talented, and motivated Ph.D. students, undergraduate students, and post-docs. In the course of my career, have graduated 29 Ph.D. students, 7 of whom are tenure-track professors at US universities (not counting post-docs). And what gets me going every morning is that I know that my work, in part, that in the world where our children will live there will be no need for hearing aids because we will be able to synthetically “write” the cochlear bone directly into the ear, where the batteries their iPhone 83’s will be able to hold charge for a year without needing re-charging, where balloons will not have to be filled up with He or any other gas but instead will be evacuated to make vacuum balloons, and where chocolate will have 100% taste, 99.9% air, and 0.01% calories. My success comes *from* being a woman, not *in spite* of being a woman. One of my key missions in life is to inspire as many young women to pursue a career in science, and especially in materials science, through mentoring, encouragement, and passing on the legacy of Bill Nix.

To reach global sustainability goals, renewable sources of hydrogen are urgently needed. Regardless of the debate over various electrochemical energy solutions and the end mix for the electrical and transportation sectors, even decarbonizing many existing chemical manufacturing processes is a large challenge directly related to existing hydrogen generation. Most industrially produced hydrogen is used for manufacturing chemicals such as ammonia, methanol, ethylene, and other hydrocarbons, and this hydrogen currently comes from fossil sources. Any effort to convert this industrial hydrogen stream to a fully renewable resource at scale will involve significant deployment of existing commercial technologies in the near term (5-10 years), while emerging technologies may play a larger role in the future.

Both liquid alkaline and proton exchange membrane-based electrolyzers have been scaled to multi-megawatt systems and are growing business segments. Both also have continued room for cost reduction and efficiency improvements, especially the PEM technology. However, fundamental understanding and process development are required to get to the targets. While most of the cell stack materials in fuel cells have been optimized for the application, electrolyzers still largely adapt existing materials for hydrogen generation. In addition, significant work has been done in developing roll to roll manufacturing methods and related quality control for PEM fuel cells, which has not yet been translated to electrolysis. Much of the learning from fuel cells can be leveraged, but needs to be applied to electrolyzer specific requirements and materials.

Collaborations will be a major element in this transition. At this stage of development, close interaction between the supply chain, electrolyzer manufacturers, and project developers all contribute to advancing towards the needed cost and performance levels. Fundamental research conducted by academia and National Labs also play a critical role. Leveraging contacts and networks built over several years in electrochemical technologies helps to bring these partners together. As a female in the field, understanding partners that value diversity and teamwork is an especially important part of this network building.

Major areas of research and development for PEM electrolysis include the polymer membrane, catalyst thrifting, automated component fabrication and assembly, and porous transport layer development. In this talk, some historical perspective on development of alkaline and PEM electrolysis will be described, with details presented on paths forward, especially in the PEM systems. Career experiences in the electrochemistry field including how to manage obstacles and opportunities from the perspective of a female scientist will also be discussed.

The compound CsH₂PO₄ (cesium dihydrogen phosphate) has emerged as a viable electrolyte for intermediate temperature electrochemical cells, devices for interconversion between electricity and value-added chemical compounds. Cesium dihydrogen phosphate is a member of the general class of materials known as solid acids or acid salts, in which polyanion groups are linked together via hydrogen bonds and monoatomic cations provide overall charge balance. Several such solid acids display a superprotonic transition, at which the material transforms to a high conductivity phase with a high degree of polyanion rotational disorder. At the transition the conductivity jumps by as much as 5 orders of magnitude and the activation energy for proton transport drops to 0.35 eV or less. In the case of CsH₂PO₄ the transition occurs at 228 °C and the conductivity reaches ~ 10^-2 S/cm at 240 °C, enabling electrochemical device operation at temperatures between 230 and 260 °C. The physical characteristics of CsH₂PO₄ imply a number of realized and potential advantages for their application in fuel cells, electrolyzers, and electrochemical hydrogen pumps relative to polymer, solid oxide, and liquid electrolyte alternatives. We present here an overview of the transport characteristics of superprotonic solid acids and the current status of electrochemical technologies based on these electrolytes.

I will share my personal perspective on the challenge and joy of being a woman in science and engineering. High energy long life rechargeable battery is considered as key enabling technology for deep de-carbonization. Energy storage in the electrochemical form is attractive because of its high efficiency and fast response time. Besides the technological importance, electrochemical devices also provide a unique platform for fundamental and applied materials research since ion movement is often accompanied by inherent complex phenomena related to phase changes, electronic structure changes and defect generation. In this seminar, I will discuss a few new perspectives for energy storage materials including new fast ion conductors, new intercalation compounds and their interfacial engineering. With recent advances in characterization tools and computational methods, we are able to explore ionic mobility, charge transfer and phase transformations in electrode materials in-operando, and map out the structure-properties relations in functional materials for next generation energy storage and conversion. Moreover, I will discuss a few future priority research directions for electrochemical energy storage.

The research-intensive STEM (science/technology/engineering/math) environment—for all its renowned innovation and productivity—has only glacially incorporated the STEM talent endemic to humankind. And science really is too important to be left just to men [1]. Besides, we have never run the control experiment to assess just how well science and society will be served by inclusion, retention, and celebration of the STEM talent endemic to humankind. In short: we need a better culture. We have four mechanistic levers to work the problem: Revolution (such as when I proposed Title IX assessments of STEM departments in 2000 [2,3] and the General Accountability Office agreed in 2004); Subversion (always in fashion); Climate Change (creating a human-centric, innovative microclimate); and Market Forces (steering the talent and the funds to healthy, productive microclimates). Our team at the U.S. Naval Research Laboratory* has created such a microclimate. A key component of our success (recognized by awards and eager collaborators) is inclusion of full-time undergraduate researchers who step away from campus to spend six-to-twelve months working with a scrum (because we love disordered materials) of Ph.D. staff and postdoctoral associates on frontier research in nanomaterials, energy storage and conversion, catalysis, and chemical threat mitigation. And we have great fun doing so.

* Rolison heads the Advanced Electrochemical Materials Section at the U.S. Naval Research Laboratory (NRL). The views are those of the author and are not necessarily those of the NRL or the U. S. Department of Defense.

[1] D.R. Rolison in L.D. Madsen: Successful Women Ceramic and Glass Scientists and Engineers: 100 Inspirational Profiles, Wiley (2016), pp. 467–472.
[2] D.R. Rolison, C&EN 2000, 78(11), 5 (13 March).
[3] D.R. Rolison, “A ‘Title IX’ challenge to academic chemistry… or… Isn’t a millennium of affirmative action for white men sufficient??” in Women in the Chemical Workforce, National Academy Press (2000), Ch. 6, pp. 74–88.

Understanding transport mechanisms in geometrically confined layered conducting inorganic membranes and solid electrolytes is paramount for next generation batteries and separation application. Ion transport is widely studied in an array of applications from batteries, to colloid science, to biological applications, and separations. Each of these applications rely on ion mobility in confined regions where the pore sizes are comparable to the Debye screening length. At these dimensions, biophysicists have observed efficient transport and selectivity mechanisms. Yet, it is still not understood how water and ions move in structural domains between 1-10 nm. Electrically tunable solid-state nanochannels may offer additional pathways for tailoring transport and controlling fundamental interactions that govern separations processes (desolvation, adsorption, selectivity, etc.). This talk intends to describe the role long-range mirostructural (tortuosity, constriction, etc.) and short-range (electric double layer, confined water) structural properties impact transport in solid electrolytes and separation membranes. To accomplish this goal, this talk will discuss a range of non-equilbrium techniques (spectroscopy, imaging, etc.) to probe solid|liquid and solid-solid interfaces in order to directly observe water and ion transport processes. The talk will also give a broader lens on women in engineering and tools to finding your community.

For the symposium subject of "Women in Materials Science", my experiences as a scientist contracting with NASA may be of interest. My first interaction with NASA was through my previous company, Ceralink Inc., in 2010. I founded Ceralink in 2000 to provide feasibility and scale up studies for energy saving processes, including the use of microwave energy. Ceralink demonstrated feasibility of microwave sintering for lunar and Martian regolith sintering through SBIR grants (Small Business Innovative Research). Ceralink's work resulted in the largest dense samples of microwave sintered lunar simulant (JSC-1A) to date. NASA is moving forward with construction on the moon and invited me to define a scope of work to lead the Microwave Sintering team. In my current role as a Professor of Ceramic Engineering at Alfred University, I am engaging undergraduate and graduate engineering students in this mission. This includes the development of synthetic lunar minerals, as well as process design for energy efficient and uniform microwave heating. I would be delighted to share some stories of getting out of my own way, accepting my position as a world expert in microwave and materials and interactions, and getting comfortable with how much I don't know and don't have to know to still be a valuable member of an amazing NASA team.

Polymer nanocomposites have been proposed as next-generation lightweight structural materials for applications ranging from aerospace to automotive and sports equipment. However, their processing often requires high temperatures for hours (or sometimes days), contributing to their energy footprint.[1] Additionally nanocomposite manufacturing techniques, such as dispersion of nanofillers in polymer solutions and resin infusion in nanoporous assemblies, often result in composite systems with heterogeneous morphologies and therefore reduced mechanical properties. We present a scalable, low-temperature nanocomposite manufacturing method called in-situ interfacial polymerization (ISIP), which is based on interfacial polycondensation of high-performance polymers in nanoporous assemblies. For example, we demonstrate that dense carbon nanotube (CNT)-polymer composites can be obtained by ISIP within CNT networks.[2] Uniform aramid-CNT composite sheets obtained by this method have a Young’s modulus of 31 GPa and a tensile strength of 776 MPa, which is a two-fold increase compared to the pristine CNT sheets. We also present how ISIP can be extended to a broad range of polymers and matrices including nanofiber mats and 3D printed lattices. A macrokinetics model describing the simultaneous fluid flow and polymerization reaction is used to predict final composite morphology and performance. We also demonstrate the implementation of ISIP as a roll-to-roll process, where the nanoporous substrate is continuously drawn through the series of liquid immersion steps to produce the final composite fiber.

We also share the personal experience of a woman in STEM and Materials Science and Engineering (MSE) from technical high school in France to graduate school in the United States. While women represent 44% of the total workforce in the US, they constitute 39% of materials scientists and chemists, and only 16% of materials engineers.[3,4] Notably, the proportion of women decreases with increasing degree level in higher education in MSE in both France and the US. We will put the underrepresentation at the highest level of the field in relation with the social psychology topic of stereotype threat: a type of social identity threat that occurs when one fears being judged in terms of a group-based stereotype.[5,6] Last, we will discuss current ongoing initiatives at MIT targeted at mitigating stereotype threat and reducing these inequalities in the laboratory and the classroom.

[1] C. A. C. Chazot and A. J. Hart, “Understanding and control of interactions between carbon nanotubes and polymers for manufacturing of high-performance composite materials,” Compos. Sci. Technol., vol. 183, p. 107795, Oct. 2019, doi: 10.1016/J.COMPSCITECH.2019.107795.
[2] C. A. C. Chazot, C. K. Jons, and A. J. Hart, “In Situ Interfacial Polymerization: A Technique for Rapid Formation of Highly Loaded Carbon Nanotube-Polymer Composites,” Adv. Funct. Mater., vol. 30, no. 52, p. 2005499, Dec. 2020, doi: 10.1002/adfm.202005499.
[3] “A Report on the Workshop on Gender Equity in Materials Science and Engineering,” College Park, Maryland, 2008. Accessed: Jun. 15, 2021. [Online]. Available: https://www.nsf.gov/mps/dmr/BroadeningPresentations/gewreport.pdf.
[4] C. Corbett and C. Hill, Solving the equation: The Variables for Women’s Success in Engineering and Computing. Washington, DC: American Association for University Women, 2015.
[5] M. C. Murphy, C. M. Steele, and J. J. Gross, “Signaling threat: How situational cues affect women in math, science, and engineering settings,” Psychol. Sci., vol. 18, no. 10, pp. 879–885, Oct. 2007, doi: 10.1111/j.1467-9280.2007.01995.x.
[6] S. J. Spencer, C. M. Steele, and D. M. Quinn, “Stereotype Threat and Women’s Math Performance,” J. Exp. Soc. Psychol., vol. 35, no. 1, pp. 4–28, Jan. 1999, doi: 10.1006/jesp.1998.1373.

Solution-processed quantum dots (QDs) are finding real-world applications in a wide-range of technologies from displays and lighting to photovoltaics and photodetectors. We take advantage of an expanded “structural toolbox” to synthesize QDs with novel and optimized photophysical properties relevant for device implementation. We use advanced heterostructuring that employs interfacial alloying, bandgap engineering, thick (“giant”) or asymmetric shell growth, etc. In this way, we have synthesized QDs for which non-radiative processes, such as blinking, Auger recombination and photobleaching, have been suppressed or even “turned off” at room temperature,^1-7 or at elevated temperatures while exposed to atmospheric oxygen.^8-9 This has required simultaneous development of new methods for evaluating correlations between synthesis, resulting nanostructure and realized functionality toward the ideal of a materials-by-design approach to the next generation of useful QDs. In this talk, I will review highlights of our work in this area, as well as some of the enabled device demonstrations. I will also discuss the integration of QDs with other functional nanomaterials for multifunctionality or emergent properties, as well as into devices, especially scanning-probe-enabled fabrication of single-photon sources.¹⁰
The journey from materials discovery to demonstrated application is long and complex, but equally so are the personal journeys of the scientists and engineers pursuing this path. In the theme of this symposium, I will conclude my presentation with some observations, concerns and aspirations for women in science made over the course of more than 20 years as a national lab technical staff member.
Krishnamurthy, S. et al. PbS/CdS Quantum Dot Room-Temperature Single-Emitter Spectroscopy Reaches the Telecom O and S Bands via an Engineered Stability. ACS Nano 2021 15, 575.
McBride, J. R. et al. Role of shell composition and morphology in achieving single-emitter photostability for green-emitting “giant” quantum dots. J. Chem. Phys. 2020, 152, 124713.
Dennis, A. M., et al. Role of Interface Chemistry in Opening New Radiative Pathways in InP/CdSe Giant Quantum Dots with Blinking-Suppressed Two-Color Emission. Adv. Funct. Mater. 2019, 29, 1809111.
Hanson, C. J. et al. Giant PbSe/CdSe/CdSe Quantum Dots: Crystal-Structure-Defined Ultrastable Near-Infrared Photoluminescence from Single Nanocrystals. J. Am. Chem. Soc. 2017, 139, 11081.
Mishra, N. et al. Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods. Nature Commun. 2017, 8, 15083.
Dennis, A. M. et al. Suppressed Blinking and Auger Recombination in Near-Infrared Type-II InP/CdS Nanocrystal Quantum Dots. Nano Lett. 2012, 12, 5545.
Ghosh, Y. et al. New Insights into the Complexities of Shell Growth and the Strong Influence of Particle Volume in Non-Blinking “Giant” Core/Shell Nanocrystal Quantum Dots. J. Am. Chem. Soc. 2012, 134, 9634.

Colloidal semiconductor nanocrystals (NCs) are typically 2-20 nm diameter fragments of the bulk solid. They are known as “artificial atoms” or quantum dots since electrons, holes, and excitons are quantum-mechanically confined and occupy discrete electronic states. The research community has celebrated >30 years of study of the synthesis, assembly, structure, properties, and applications of colloidal semiconductors NCs, and I have enjoyed the opportunity to contribute to the field in my career. Advances in wet-chemical synthetic methods enable the preparation of NCs tailorable in size, shape, composition, and surface chemistry. As colloids, these NCs are readily dispersed in solvents and deposited using solution-based methods. They can self-assemble to form glassy or crystalline NC solids or be directed to assemble to deterministically position single or countable numbers of NCs. I will focus on routes to design solid-state NC materials by manipulating the NC surface chemistry to strengthen electronic coupling, by exchanging the ligands used in synthesis for more compact chemistries, and NC doping, by introducing atoms and ions that serve as impurities or modify stoichiometry. Ultimately, I will connect NC material design to their physical properties and their application in (un)conventional electronic and optoelectronic devices. I will also give an outlook on the opportunity to exploit NCs as platforms for quantum information science, in particular as optically addressable qubits.

In bioinorganic chemistry, metal ions play important roles in the structure and function of a variety of systems. Using this as inspiration, our approach is to design materials that exploit metal coordination bonding to create materials with unique properties. Of particular interest, are materials that coordinate Fe and V ions, since once coordinated, the metal-ligand bonding in the material can be controlled with light using photochemical processes Both Fe(III) and V(V) coordination in polysaccharide materials can be used to create hydrogels. Once irradiated, photo-induced charge transfer processes change the Fe and V coordination environments in the gel, and disrupting the intermolecular forces in the material, changing the viscosity and modulus of the gels. These photoresponsive materials can be used for a variety of applications, including encapsulation and delivery of bioactive molecules or nutrients.

The design of new materials has often relied on crystal structure as a primary source for design complexity and innovation, requiring new crystal structures and new manners of constructing and synthesizing these structures. Within the photonics community, where the goal is a photonic crystal, i.e., a crystal that reflects a range of wavelengths, the literature points to a handful of targets, most commonly the diamond or inverse opal structures. Nanoparticle self-assembly, or the spontaneous emergence of order due to particle interactions, has been identified as a favorable synthesis route, as photonic nanocrystals reflect wavelengths within the visible range due to the scale-covariance of photonic band structures. Yet, the effort to self-assemble photonic crystals has been fraught with obstacles — from difficulty synthesizing diamond to the degradation of photonic band gaps based upon thermal noise within the assembly. This begs the question: if we look beyond the known set of photonic crystal structures, which other structures are worth targeting? We discuss the unexpectedly diverse range of crystallographic structures that will support a photonic band gap, as determined by more than 150,000 photonic band structure calculations. These calculations identify nearly 300 previously unstudied targets for photonic crystals—including targets achievable via colloidal self-assembly [1]. We demonstrate avenues to predict the polyhedral nanoparticles that can cleanly self-assemble these targets and the implications, both good and bad, that small changes to nanoparticle shape have on the resulting crystal’s behavior [2-4].

Finally, we discuss the topic of scientific communication, which is fundamental in encouraging underrepresented populations in STEM by deterring the imposter syndrome for those who may glean a sense of “otherness” from poorly communicated work. We will focus on two programs at the University of Michigan to connect higher education institutions with primary and secondary school educators [5],[6]. These programs facilitate and promote discourse between graduate students and K-12 STEM educators, pushing students to communicate and contextualize their research and extending access to cutting-edge science to populations typically harder to reach via other outreach efforts.

[1] R. K. Cersonsky, J. Antonaglia, B. D. Dice, S. C. Glotzer, "Unexpected Diversity of Three-Dimensional Photonic Crystals,” (2021). Nature Communications. https://www.nature.com/articles/s41467-021-22809-6
[2] R. K. Cersonsky, G. van Anders, P. M. Dodd, and S. C. Glotzer, "Relevance of Packing in Colloidal Self-Assembly," (2018). Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1720139115.
[3] R. K. Cersonsky, J. Dshemuchadse, J. Antonaglia, G. van Anders, S. C. Glotzer, "Pressure–Tunable Band Gap in an Entropic Crystal", (2018). Phys. Rev. Mat. https://doi.org/10.1103/PhysRevMaterials.2.125201.
[4] Y. Zhou, R. K. Cersonsky, S. C. Glotzer, "A New Route to the Diamond Colloidal Crystal.” In preparation.
[5] R.K. Cersonsky, LL Foster, T Ahn, RJ Hall, HL Van Der Laan, TF Scott. “Augmenting Primary and Secondary Education with Polymer Science and Engineering,” (2017). Journal of Chemical Education 94 (11), 1639-1646. https://pubs.acs.org/doi/full/10.1021/acs.jchemed.6b00805
[6] A Travitz, A Muniz, JK Beckwith, R.K. Cersonsky. “Bringing Science Education and Research together to REACT,” (2021). American Society for Engineering Education, 1-13. https://doi.org/10.18260/1-2--35030

Colloidal nanocrystals are attractive as solution-processable precursors to make conductive thin films for electronic and optoelectronic devices. However, in most cases electrons move through nanocrystal films by thermally activated hopping, behaving as insulators even when the nanocrystals themselves are metallic. We synthesize indium tin oxide transparent conducting nanocrystals to fabricate conductive thin films and show how the contact resistance between them controls the metal-insulator transition. Our results establish a “phase diagram” for electron transport, mapping conditions for hopping, thermally activated granular metallic, and classical metallic conduction.

From the perspective I now have – participating regularly in faculty recruiting, promotion, and mentorship – I have started to see experiences from my own early career in a broader context. Reflecting on these, I’ll talk briefly about the ways that prevalent stereotypes present barriers to the development and advancement of women and people from underrepresented groups in STEM.

Although semiconductor quantum dots (QDs) are excellent fluorophores for biosensing and biomedical imaging, their translation to clinical applications is stymied by toxicity concerns. While materials developed for optoelectronic applications such as displays and photovoltaics exhibit excellent photophysical properties, their elemental composition is often contraindicated for use in human subjects. The current solution to elemental toxicity is to cap the core nanoparticle in a shell, usually of zinc sulfide, to prevent the release of the offending elements into the biological environment. This sequestration approach also results in the accumulation and persistence of the nanoparticles in the liver, an outcome that would preclude FDA approval for a diagnostic contrast agent. This combination of toxic compositions and bioaccumulation is a persistent barrier to the clinical translation of semiconductor nanoparticles.

In our new approach to developing inorganic nanoparticles for biomedical imaging and in vivo biosensing applications, we have shifted our focus to consider biological interactions first and optical properties second to identify the best materials for the application. Developing inorganic nanomaterials that can be used as contrast agents in humans requires addressing issues of toxicity, bioaccumulation, and function. We are inspired by the composition of the only FDA-approved inorganic nanoparticle: iron oxide. Iron oxide nanoparticles degrade in vivo into biocompatible and bioessential elements, coincidentally treating the patient’s anemia. To develop biocompatible inorganic nanoparticles (bioNPs), we are synthesizing nanocrystals comprising bioessential elements and assessing their optical properties, degradation, and nanotoxicity. These iron- and copper-based semiconductors are often understudied with regards to both their optoelectronic properties and biocompatibility. For example, we have demonstrated that while copper indium sulfide (CIS) QDs exhibit appropriate optical properties for in vivo luminescence imaging, ZnS shell-free CIS particles degrade rapidly with high toxicity in mice. Alloying zinc into the particles (CISZ) improves their optical properties, maintains a reasonable degradation rate, and substantially reduces toxicity. In comparison, copper iron sulfide nanoparticles (chalcopyrite or bornite; abbreviated CFS) biodegrade and exhibit localized surface plasmon resonance (LSPR) in the NIR, showing promise for photoacoustic imaging and photothermal therapy applications. As we expand the compositions of the bioNPs tested, we are developing a framework to relate the degradation rate and degradation products to toxicity. This information is being used together with the optoelectronic properties of the new materials to change the way we develop semiconductor nanoparticles for in vivo applications.

Despite the current battery technology evolution, battery chemistries have not changed much in the last two decades. Highly emerged EV market evokes the demands on advanced batteries with high energy density. Among the future chemistries, lithium metal batteries have great advantages over state-of-the-art lithium ion batteries in term of energy density and cost, which bring huge opportunity for long-range and low-cost electrical vehicles in the future. However, automotive industry has critical requirements on specific characteristics of battery cells. In this talk, I will discuss the requirements for future electrical vehicle application and the impact of Li-metal batteries on automotive industry. As a women scientist working in the automotive industry, I will also describe the range of opportunities available to women in this field. Some concerns and challenges will also be discussed.

This talk will provide an overview of our multidisciplinary approach to elucidate the interfaces between living and non-living matter, and how we use this fundamental knowledge to design innovative materials and technologies with impactful applications in regenerative medicine, advanced therapeutic delivery and disease diagnostics.
We engineer simple conceptually novel biosensing approaches using designer bio-nanomaterials for ultrasensitive diagnostic assays that are simple, cost-effective and easy deploy to the point-of-care. We are exploiting the sensing capabilities of nanoparticles to engineer paper-based lateral flow immunoassays (LFIAs) for the detection of infectious diseases such as HIV [2], Ebola, tuberculosis and Covid-19, and we can integrate our assays with smartphone technology for patient self-monitoring, geographical tagging and epidemic surveillance [3]. Harnessing our knowledge of the bio-interfaces, we also engineer complex 3D architectures with spatially arranged biochemical cues and cell interfacing nanoneedles for multiplexed intracellular biosensing at sub-cellular resolution and modulation of biological processes [4].
I will also speak about the breakthroughs, innovations and aspirations that shape who we are and what we do, and how we strive to create an inclusive and stimulating environment where science and scientists flourish.

[1] P. D. Howes… M. M. Stevens. “Colloidal nanoparticles as advanced biological sensors.” Science. 2014. 346: 53-63.
[2] C. Loynachan… M. M. Stevens. “Platinum nanocatalyst amplification: redefining the gold standard for lateral flow immunoassays with ultra-broad dynamic range.” ACS Nano. 2018. 12(1): 279-288.
[3] C. S. Wood… M. M. Stevens. “Taking connected mobile-health diagnostics of infectious diseases to the field.” Nature. 2019. 566: 467-474.
[4] C. Chiappini… M. M. Stevens, E. Tasciotti. “Biodegradable silicon nanoneedles delivering nucleic acids intracellularly induce localized in vivo neovascularization.” Nature Materials. 2015. 14: 532-539.

In this talk, I will reflect on my journey working with flexible electronics from my early career to defining a new field of skin-inspired electronics. I will talk about lessons learned through this journey.

We present our research, education, outreach, and translational work to control light at the nanoscale for infectious disease diagnostics, including detecting bacteria at low concentration, screening for viral gene sequences, and visualizing in-vivo inter-cellular forces. First, we combine Raman spectroscopy and deep learning to accurately classify bacteria by both species and antibiotic resistance in a single step. We design a convolutional neural network (CNN) for spectral data and train it to identify 30 of the most common bacterial strains from single-cell Raman spectra, achieving antibiotic treatment identification accuracies exceeding 99% and species identification accuracies similar to leading mass spectrometry identification techniques. Our combined Raman-CNN system represents a proof-of-concept for rapid, culture-free identification of bacterial isolates and antibiotic resistance. Second, we describe resonant nanophotonic surfaces, known as “metasurfaces” that enable multiplexed detection of SARS-CoV-2 gene sequences. Our metasurfaces utilize guided mode resonances excited in high refractive index nanostructures. The high quality factor modes produce a large amplification of the electromagnetic field near the nanostructures that increase the response to targeted binding of nucleic acids; simultaneously, the optical signal is beam-steered for multiplexed detection. We describe how this platform can be manufactured at scale for portable, low-cost assays. Finally, we introduce a new class of in vivo optical probes to monitor biological forces with high spatial resolution. Our design is based on upconverting nanoparticles that, when excited in the near-infrared, emit light of a different color and intensity in response to nano-to-microNewton forces. The nanoparticles are sub-30nm in size, do not bleach or photoblink, and can enable deep tissue imaging with minimal tissue autofluorescence. We present the design, synthesis, and characterization of these nanoparticles both in vitro and in vivo, focusing on the forces generated by the roundworm C. elegans as it feeds and digests its bacterial food. Beyond the rigor of research, I also describe how I am reliving my childhood with my two young sons, and exploring the country as an avid cyclist and long-distance runner.

In my presentation, I will talk about my academic journey as a young Egyptian woman and the path that led me to studying and working in computational materials science. I will describe our recent work on a multiscale modeling and simulation study of a high entropy alloy (HEA) system by combining continuum level thermodynamic modeling, atomic scale quasi-random structures, and electronic structure density functional theory (DFT). The main aim of this study is to provide a framework that can aid with and potentially accelerate the exploration of the massive HEA composition space through guiding experimental efforts.

Computational phase diagrams of four subsystems of the CoCrFeNiTi HEA system were constructed using the calculation of phase diagrams (CALPHAD) method. Our efforts were focused on the single phase face-centered cubic (FCC) regions in the obtained diagrams, due to the potentially favorable properties of alloys with this structure. A thermodynamic analysis was also carried out, in which we studied the variations in the mixing enthalpies and entropies within the studied systems. From our analysis, we were able to determine the main stabilizing factor (enthalpy vs. entropy) of the single FCC phase as a function of temperature. Furthermore, we tested the possibility of changing the thermodynamic phase diagram of this alloy system upon dissolution of impurities such as carbon and oxygen.

The constructed phase diagrams were then used to guide composition selection for an alloy to study its mechanical properties using first-principles DFT calculations. The selected alloy with composition CoCrFeNi_1.75Ti_0.25 was modeled using the special quasi-random structure (SQS) approach and DFT calculations were used to determine the elastic constants matrix of this alloy composition in addition to its stress-strain response under a uniaxial load. Additionally, we analyzed the hypothesis of sluggish diffusion in HEA via computing the formation energies of all possible vacancies in the alloy. Our coupled CALPHAD-SQS-DFT approach provides a general methodology for understanding the thermodynamics and mechanics of non-equiatomic HEAs.

In addition to the technical aspects related to the HEA work, I will be sharing my experience and some aspects of my personal life, with an emphasis on the things that have helped me overcome the obstacles that women in STEM face. My interest in materials science was sparked early on when I was still an undergraduate student, which led me to volunteer as a research assistant on a project focused on synthesizing and characterizing aluminum-graphene composites. Although I started my M.Sc. thesis as an experimentalist working on studying HEAs, the Covid-19 pandemic imposed a shift of my project to a fully computational study, after which I successfully obtained my M.Sc. degree. Upon finishing my thesis and facing a delay in my PhD plans due to the Covid-19 pandemic, I worked on a research project at the interface between materials science and biochemistry in which I employed molecular dynamics simulations to study the effect of certain small molecules on the binding affinity of the SARS-CoV-2 virus to the ACE2 human enzyme.

Finally, I will conclude my presentation with a discussion of my future plans, which include obtaining a PhD degree in modeling of heterogeneous systems, as well as how my goals have been shaped by my experiences and previous research.

Women have, throughout history, played an important role in materials science. In recent times, our role has grown strongly and we have become more prominent. So things are improving, but I believe we still face many challenges, some well recognized and spoken about openly, but others that are more hidden and hence not addressed or spoken about. Based on my own experiences, I will try to address some of challenges I have faced and will discuss how I have (or have tried to) overcome them. I will move on from here to show examples of my recent work demonstrating the important role of materials science in the engineering of oxide electronic thin films for low power electronics and energy applications.

The development of liquid cells for transmission electron microscopy (TEM) has enabled breakthroughs in our ability to follow nanoscale structural, morphological, or chemical changes during materials growth and applications. Time-resolved high-resolution imaging and chemical analysis through liquids have opened the opportunity to capture nanoscale dynamic processes of materials, including reaction intermediates and the transformation pathways. In this talk, I will present a series of work in my group on liquid cell developments and in situ liquid cell TEM study of nanocrystal growth and transformations, lithium dendrite formation and suppression and using liquid cell TEM in other studies on materials dynamics. The understanding garnered accelerates the discovery of novel materials for applications in energy storage, catalysis, and other functional devices.

The Energy sector has low diversity and gender equality into its workspaces and boardrooms. Based on some statistics, only 14% of energy engineers are women. This testifies that we need to take serious steps to improve the gender diversity in the energy sector. Women at leadership positions, in boardrooms and in factory floors can be achieved in two ways: 1) male dominant hiring managers can help to promote women engineers for the leadership positions, 2) mentoring and supporting younger women generations in engineering and helping them to become more visible and confident. In my presentation, I will focus on my research about Li-ion batteries and their applications in electric vehicles and my journey as a women academic engineer being the first women tenure-track faculty hired for the engineering college in 2001, and also being the only women full-professor in the engineering college today.

At the UC Davis College of Engineering, we've launched a new commmunications platform titled Engineering an Inclusive Future: https://engineering.ucdavis.edu/engineering-inclusive-future. This new platform highlights how much we’ve done—and how much more we will be doing—to move the College of Engineering toward “inclusion excellence,” in which all members of a community are encouraged and supported to work, study and learn in a way that allows each of us to reach our full potential. For this effort, I wanted to take a chance and show not just our best work but areas where we can improve, so we’ve employed first-person storytelling from our students, faculty, staff and postdocs. We post one to two stories a month and share these on our social media channels. Sometimes these stories are less than rosy, but this transparency helps stimulate conversation and reveals a deeper need to discuss challenges faced by women and underrepresented groups across our constituencies.

In addition, I've been part of a larger effort in collaboration with colleagues at the Northern California UC campuses (Davis, Berkeley, Santa Cruz, San Francisco), as well as Berkeley Lab, titled Imagining an Anti-Racist UC: https://www.ucop.edu/human-resources/coro/2020_forms/coro_nor-cal_2020_executive_summary.pdf. This effort aims to facilitate learning, reflection and performance assessment processes with respect to anti-racism among UC supervisors/leaders. Despite being the third largest employer in California, the racial/ethnic demographics of our senior professionals and management do not reflect the racial/ethnic demographics of the UC workforce, or our state.

To address this need, we developed an Anti-Racism Learning and Reflection Tool that establishes guiding anti-racism principles and practices that can be applied uniformly across the UC system by leaders, supervisors and managers to better communicate and carry out anti-racist core values and cultivate a climate of belonging for our staff. While each UC campus has a performance review process and evaluation tool that includes consideration of diversity, equity and inclusion, these materials do not currently incorporate a focus on anti-racist principles and practices. This tool aims to support the life-long learning of managers by offering a framework for them to advance racial equity principles and practices in hiring, performance review, promotion, and workplace climates for staff. I will present this tool and share learnings from its implementation at UC Davis.