(6ll) Multiscale Framework to Engineer Non-Equilibrium Responses at Complex Materials Interfaces

Materials design is at the forefront of many pioneering technological advancements. One notable direction has been to leverage unique behavior that arises at the interface of dissimilar constituents or phases, e.g., nanomaterials, complex fluids, and soft condensed materials. The additional interactions at these interfaces typically induce molecular restructuring that deviates from the characteristic order found in bulk counterparts. Intriguingly, such subtle microscopic changes tend to propagate to functionally-relevant macroscopic responses. The exploration of this idea is the central theme of my research program.

I seek to investigate fundamental molecular driving forces at materials interfaces that can be leveraged to address global challenges in energy, sustainability, and healthcare. In particular, my research group will focus on systems that are inherently out-of-equilibrium, and elucidate structure-kinetic-function relationships in order to engineer the dynamical behavior at these interfaces. My strategic approach will be to systematically study collective molecular behavior using the multiscale computational expertise that I have developed throughout my graduate and postdoctoral training. The primary benefit of such an approach is the ability to isolate individual factors through creative simulation design, which would otherwise be untenable in experimental systems. Relatedly, methodological developments will be pursued to address problem-specific challenges, as exemplified throughout my research career. My long-term goal is to establish foundational practices for materials development based on non-equilibrium strategies and computationally-guided design. To this end, I will initially focus on the following four programs:

Program 1: Plastic Crystal Electrolytes for Alkali-Metal Batteries

Program 2: Nanoporous Electrode Materials for Capacitive Deionization

Program 3: S-Layer Proteins for Programmable 2D Nanoporous Assemblies

Program 4: Virus-Inspired Nanocarriers for Drug Delivery

Research Background:

Throughout my scientific career, I have been fascinated by the ability of materials to adopt versatile macroscopic responses on the basis of microscopic changes at interfaces. This foundational paradigm has led to fundamental structure-function relationships that have rapidly accelerated technological innovation and represents an important example of fundamental science meeting engineering principles. The study of material responses at interfaces has been a consistent theme throughout my research to date. For example, my graduate work identified new means to influence collective ion and electrode charge reorganization for supercapacitor applications by engineering interfacial chemistry^1-5 and confinement^6-7 using carbon nanomaterials. My postdoctoral work identified mechanistic principles of protein self-assembly, membrane remodeling, and RNA scaffolding that collectively regulate viral morphogenesis.^8-9 An integral aspect of these past studies was the development and use of hierarchical (or multiscale) computer simulations that rigorously bridge insights from quantum mechanical (QM), molecular, and coarse-grained (CG) resolutions to connect with experiments. For instance, representing electrode polarization classically (from QM data) was critical for my work in supercapacitors.^1-7 I have also advanced new methodologies for CG modeling based on both experimental data and statistical mechanics.^8-12 Importantly, the transfer of information between scales allows these models to directly interrogate the importance of identified microscopic behavior on collective macroscopic properties. During my research career, I intend to utilize the versatility afforded by my training in these multiscale techniques and continue to advance frontiers in computational methods.

Successful Proposals: Ruth L. Kirschstein National Research Service Award (NIH F32)

Postdoctoral Project: “Multiscale Simulations of HIV-1 Assembly, Budding, and Maturation” under the supervision of Gregory A. Voth, Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago

PhD Dissertation: “First-Principles Investigation of Carbon-Based Nanomaterials for Supercapacitor” under the supervision of Gyeong S. Hwang, McKetta Department of Chemical Engineering, The University of Texas at Austin

Teaching Interests:

Throughout my training, my mentors have been invaluable for my growth as an independent scientist and engineer. As a faculty member, I eagerly look forward to my responsibility as a mentor for the next generation of young scientists. My core teaching philosophy can be described by the following three principles. My foremost goal is to instill a passion for learning by fostering both the curiosity and the confidence to be inquisitive without fearing failure. To this end, I have enjoyed preparing activities that enable students from local schools (from elementary to high school levels) to interact with interesting concepts from my research, e.g., seeing “self-assembly” in action. My second goal is to create tangible connections between what students learn in academic settings and real-world problems. For this reason, I firmly believe in the value of immersive, project-based learning as a supplement to lectures. Not only do these projects translate engineering skills toward problem solving, but also establish communication and collaborative skills. In fact, one of my undergraduate courses followed this model and eventually inspired me to pursue computational research. My third aim is to create an environment for my students to question underlying assumptions and to develop physical intuitions. As a teaching assistant, I have found that one of the best forums for this discourse emerges from thought-experiment challenges through rigorous debate within small student clusters. Finally, I am encouraged by the increasing ubiquity of molecular visualization tools and online educational platforms, and I will strive to translate concepts from my own research into accessible, interactive, and transparent form factors to engage future scientists.

While I am prepared to teach any core chemical engineering course, I am most interested in thermodynamics, statistical mechanics, or numerical methods. I am also looking forward to developing new courses based on my core competencies, such as a broad introduction to the growing field of computational molecular sciences.

Selected Publications:

1. Paek, E.; Pak, A. J.; Kweon, K. E.; Hwang, G. S., On the Origin of the Enhanced Supercapacitor Performance of Nitrogen-Doped Graphene. J Phys Chem C 2013, 117, 5610-5616.
2. Pak, A. J.; Paek, E.; Hwang, G. S., Tailoring the Performance of Graphene-Based Supercapacitors using Topological Defects: A Theoretical Assessment. Carbon 2014, 68, 734-741.
3. Pak, A. J.; Paek, E.; Hwang, G. S., Impact of Graphene Edges on Enhancing the Performance of Electrochemical Double Layer Capacitors. J Phys Chem C 2014, 118, 21770-21777.
4. Paek, E.; Pak, A. J.; Hwang, G. S., Large Capacitance Enhancement Induced by Metal-Doping in Graphene-based Supercapacitors: A First-Principles-Based Assessment. ACS Appl Mater Interfaces 2014, 6, 12168-12176.
5. Pak, A. J.; Hwang, G. S., On the Importance of Regulating Hydroxyl Coverage on the Basal Plane of Graphene Oxide for Supercapacitors. ChemElectroChem 2016, 3, 741-748.
6. Pak, A. J.; Hwang, G. S., Charging Rate Dependence of Ion Migration and Stagnation in Ionic-Liquid-Filled Carbon Nanopores. J Phys Chem C 2016, 120, 24560-24567.
7. Pak, A. J.; Hwang, G. S., Molecular Insights into the Complex Relationship between Capacitance and Pore Morphology in Nanoporous Carbon-based Supercapacitors. ACS Appl Mater Interfaces 2016, 8, 34659-34667.
8. Pak, A. J.; Grime, J. M. A.; Sengupta, P.; Chen, A. K.; Durumeric, A. E. P.; Srivastava, A.; Yeager, M.; Briggs, J. A. G.; Lippincott-Schwartz, J.; Voth, G. A., Immature HIV-1 Lattice Assembly Dynamics are Regulated by Scaffolding from Nucleic Acid and the Plasma Membrane. Proc Natl Acad Sci USA 2017, 114, E10056.
9. Pak, A. J.; Grime, J. M. A.; Yu, A.; Voth, G. A., Off-Pathway Assembly: A Broad-Spectrum Mechanism of Action for Drugs That Undermine Controlled HIV-1 Viral Capsid Formation. J Am Chem Soc 2019, 141, 10214-10224.
10. Pak, A. J.; Dannenhoffer-Lafage, T.; Madsen, J. J.; Voth, G. A., Systematic Coarse-Grained Lipid Force Fields with Semiexplicit Solvation via Virtual Sites. J Chem Theory Comput 2019, 15, 2087-2100.
11. Jin, J.; Pak, A. J.; Voth, G. A., Understanding Missing Entropy in Coarse-Grained Systems: Addressing Issues of Representability and Transferability. J Phys Chem Lett 2019, 10, 4549-4557.
12. 12. Pak, A. J.; Voth, G. A., Advances in Coarse-Grained Modeling of Macromolecular Complexes. Curr Opin Struct Biol 2018, 52, 119-126.