(4cy) Multiscale Design of Fluids and Interfaces for Sustainable Water-Energy Solutions

Research Interests: The confinement of fluids within nanomaterials such as graphene nanocapillaries and carbon nanotubes induces fundamental changes in their behavior, unlocking unique properties with immense potential for sustainable separation technologies. However, translating promising atomic-level interactions into predictable, measurable macroscopic properties, like the water permeability, ion selectivity, and chemical reactivity, remains a critical bottleneck. My proposed research directly addresses this challenge by developing a multiscale design strategy that integrates quantum chemical and classical molecular dynamics simulations, continuum models, and machine learning techniques. Through the three focused research thrusts discussed below, I aim to significantly advance both our fundamental understanding of fluid-nanomaterial interactions and their practical application in discovering sustainable water-energy solutions.

Thrust 1 will focus on chemical separations, where I will utilize molecular dynamics simulations with polarizable force fields and analytical models to describe polar fluids (e.g., water and organic solvents) in contact with graphitic nanomaterials. This approach will allow us to develop design rules for membrane separations, including azeotropic mixtures which are otherwise extremely energy intensive to separate using distillation techniques. Thrust 2 will prioritize machine-learning (ML) potentials developed using a physics-based approach and trained on polarizable and ab initio molecular dynamics (MD) simulations. This approach seeks to combine the accuracy of ML approaches with theoretical frameworks which satisfy physical constraints and laws. Circumventing the black-box nature of existing ML models, the proposed approach will enable high-throughput identification of the next-generation of two-dimensional (2D) and one-dimensional (1D) nanomaterials for water purification. Lastly, Thrust 3 will utilize ML approaches and multiscale modeling to describe chemical reactions under confinement. Specifically, I will investigate the confined environments of 2D and 1D nanomaterials as nanoreactors to investigate important classes of chemical reactions, including nucleophilic substitution and elimination reactions. This will not only contribute to the goals of sustainable chemistry through the design of more efficient reaction pathways, but also enable the direct study of solvent effects and nanotube-mediated stabilization of transition states, which are unattainable in bulk solutions. Finally, while each of the three thrusts has distinct goals and applications, the computational approaches developed in the context of the proposed modeling framework are designed to be cross-cutting, offering synergistic benefits across all the three thrust areas. Moreover, leveraging my doctoral and postdoctoral expertise in modeling fluid-nanomaterial interactions, my research will integrate the predictive power of ML with the explanatory power of theoretical models, enabling multiscale modeling from the quantum to the macroscopic levels.

Past Research Experience: My Ph.D. research at MIT, supervised by Professor Daniel Blankschtein, addressed a critical gap in our understanding of electronic polarization effects at nanomaterial interfaces. These effects which are many-body in nature arise from the electric fields exerted by polar molecules like water and charged species such as salt ions at nanomaterial interfaces. Prior to my work, most classical MD simulation studies employed pair-wise additive potentials, such as the Lennard-Jones potential, to model the interactions of fluids at nanomaterial interfaces. My Ph.D. research highlighted the significant impact of polarization effects on interfacial phenomena, including wetting¹ and free energy of ion adsorption^2,3 at graphitic interfaces. This was followed by a collaborative study with Professor Aleksandr Noy’s group at the Lawrence Livermore National Laboratory (LLNL), where we demonstrated a 3-order of magnitude breakdown of the well-known Nernst-Einstein (NE) relation inside 0.8 nm diameter carbon nanotubes (CNTs).⁴ In this combined experimental and computational work featured as a cover image in Nature Nanotechnology, my simulations played a key role in 1) first showing that the significant ion-CNT polarization energy can overcome the dehydration penalty, enabling cations such as the potassium (K⁺) ion to enter the interior of narrow CNTs, and 2) provide direct evidence of ion-water cluster formation – a phenomenon causing the breakdown of the NE relation. Additionally, I collaborated with Professors Martin Bazant and Michael Strano at MIT, publishing several manuscripts contributing to the continuum modeling of electric double layers at charged interfaces and providing thermodynamic insights on graphene membranes and carbon nanotubes. Following my Ph.D., my postdoctoral research at MIT has enabled me to not only expand my technical skills but also see fruitful validation of my simulations/theory in collaboration with experimentalists. To this end, I have collaborated with the group of Professor Noy from LLNL to model water and ion transport through metallic and semiconducting carbon nanotubes;⁵ with the group of Professor YuHuang Wang from the University of Maryland, College Park, on sonication-free surfactant-based stabilization of individual carbon nanotubes in water;⁶ and with the group of Professor Michael Strano from MIT on investigating laser-induced phase transitions of water inside carbon nanotubes (manuscript in preparation). For the latter project, I developed a novel algorithm for grand canonical molecular simulations in a hybrid statistical mechanical ensemble, allowing us to investigate capillary phase transitions under non-isothermal conditions, which is different from the adsorption isotherms at constant temperature traditionally used to characterize fluids under confinement. These projects pursued during my Ph.D. and postdoctoral tenures at MIT have laid a strong foundation to undertake the multiscale challenges outlined in my proposed research.

References:

(1) Misra, R. P.; Blankschtein, D. Insights on the Role of Many-Body Polarization Effects in the Wetting of Graphitic Surfaces by Water. The Journal of Physical Chemistry C 2017, 121 (50), 28166-28179.

(2) Misra, R. P.; Blankschtein, D. Ion Adsorption at Solid/Water Interfaces: Establishing the Coupled Nature of Ion-Solid and Water-Solid Interactions. J Phys Chem C 2021, 125 (4), 2666-2679.

(3) Misra, R. P.; Blankschtein, D. Uncovering a Universal Molecular Mechanism of Salt Ion Adsorption at Solid/Water Interfaces. Langmuir 2021, 37 (2), 722-733.

(4) Li,^† Z.; Misra,^† R. P.; Li, Y.; Yao, Y.-C.; Zhao, S.; Zhang, Y.; Chen, Y.; Blankschtein, D.; Noy, A. Breakdown of the Nernst–Einstein relation in carbon nanotube porins. Nature Nanotechnology 2023, 18 (2), 177-183.

(5) Li,^† Y.; Li,^† Z.; Misra,^† R. P.; Liang,^† C.; Gillen, A. J.; Zhao, S.; Abdullah, J.; Laurence, T.; Fagan, J. A.; Aluru, N.; Blankschtein, D.; Noy, A. Molecular transport enhancement in pure metallic carbon nanotube porins. In Press, Nature Materials 2024 (doi: https://doi.org/10.1038/s41563-024-01925-w).

(6) Wang,^† P.; Misra,^† R. P.; Zhang, C.; Blankschtein, D.; Wang, Y. Surfactant-Aided Stabilization of Individual Carbon Nanotubes in Water around the Critical Micelle Concentration. Langmuir 2024, 40 (1), 159-169.

^†Equal contribution

Teaching Interests: My teaching philosophy is rooted in the simple understanding that knowledge, unlike the fleeting nature of human life, can be a lasting gift to humanity. The enduring legacy of scholars like Newton and Einstein, whose theories continue to inspire and guide us, exemplifies this principle. This has also fueled my passion for an academic career dedicated to the generation and sharing of knowledge. As a Chemical Engineering professor, I will prioritize 1) building a solid foundation in the core concepts through pedagogical explanations, physical intuition and real-world examples, 2) fostering interdisciplinary connections by highlighting how chemical engineering intersects with other disciplines (e.g., materials science, nanotechnology), 3) promoting active learning through hands-on experiences like computer simulations and design projects, 4) encouraging critical thinking and collaborative spirit in homework assignments, and 5) integrating current research findings into course materials, assignments, and discussions to spark curiosity and inspire students to pursue their own research questions. At MIT, I have had the great pleasure of serving as a teaching assistant in Fluid Mechanics (10.301) and Introduction to Interfacial Phenomena (10.43), which combined with my research expertise in molecular simulations and computational methods, have equipped me to teach a broad range of undergraduate and graduate courses in Chemical Engineering. I will be especially interested in teaching thermodynamics, statistical mechanics, computational methods, and transport phenomena. Further, I envision developing a graduate-level course titled, “Computational Approaches in Interfacial Phenomena and Nanofluidics”, which would directly build upon my educational background and previous research experience on modeling fluids at nanomaterial interfaces and under confinement. Finally, I am committed to actively engaging students at all levels by developing and leading workshops for undergraduate and high school students, creating new online courses on platforms like edX, and leveraging my teaching and research materials to create accessible and engaging learning experiences.