(4gw) Employing Shape As a Handle for Materials Design

Over the last decade, there has been an explosive growth in our capability to synthesize nanoscale building blocks (NBBs). These NBBs possess a wide range of optical, structural, magnetic, and/or catalytic properties, suggesting that they can serve as the ideal design space for materials discovery spanning a diverse range of technologically open questions/challenges. Central to these applications is the ability to regulate the structural organization of NBBs to obtain a targeted macroscopic property, and it is here that key factors holding back their usage on an industrial scale emerge. Firstly, control over structural organization is typically system-specific, making it challenging to decouple the effect of individual NBBs from the structure into which they are assembled. In cases where anisotropic NBBs are employed, specific particle-particle orientations are additionally necessary to realize the desired physical property, yet particle level control over orientation remains elusive. Secondly, even in situations where the targeted structural organizations are attained, the system often does not possess the appropriate robustness required for the intended application. Solving such problems necessarily calls for the design of multi-functional systems.

Along this vein, a novel suite of synthetic macromolecules called shape amphiphiles (SP) has recently been developed that combines buildings blocks of varying shapes. In other words, these SPs are giant molecules constructed from linking different NBBs together. Such SPs are of particular interest as they couple physical properties from multiple classes of materials. In general, the key features of SPs are: 1). linking shaped molecules together provides access to previously unobserved assembly morphologies and 2). the type of NBBs and linkage geometry/sequence employed in SP creation are design parameters for controlling macroscopic properties, providing an unlimited set of molecular handles for use in materials engineering. Due to the potentially infinite space of ways with which NBBs can be connected together, a systematic exploration across all relevant linkage geometry, sequence, and sizes become experimentally intractable. As a result, the current open challenge lies in defining strategies aimed at figuring out which combinations of NBBs can exhibit the structural and physical properties relevant for applications in optical, electronic, catalytic, and/or biological materials. Such a question readily falls within the playground of computational and inverse design.

Here, we propose a framework inspired by nature for creating complex proteins and biological molecular machines from the 20 basic amino acids. Nature achieves this level of precision via the order with which it strings together the various amino acids (AA). Analogously, our library of monomeric NBBs can be viewed as the synthetic counterpart to the 20 amino acids. Similar to the primary sequence of a protein, we simply seek to leverage how to combine NBBs together to produce SP designs with relevant properties. Much of the current experimental work focus at the level of NBB dimerization due to a lack of guidance on ways to further generalize SPs connections to more than two building blocks species: that is, trimers, tetramers and beyond. In fact, there already exist synthetic techniques that enable the creation of chains of NBBs up to several microns in length. But, lacking the ability to control chain folding, these polymeric NBBs are limited to simple rod-like assemblies. Once we elucidate proper understanding of SP assembly across different degrees of NBB polymerization, we can leverage such knowledge to create nano-machines via directed folding of NBB chains, much like how nature creates biological machines using polymeric chains of AAs. Our goal seeks to develop a framework for modeling the structure-property relationships for systems of linked NBBs ranging from dimer to polymeric chains that can then be used for the inverse design of multi-functional materials and synthetic molecular machines.

Teaching Interest

My primary philosophy in regard to teaching revolves about the central idea of helping students acquire a fundamental understanding of the materials while simultaneously providing them with ways to develop the relevant skills required to become an effective professional or researcher in their respective field. With regard to lecturing, I believe that this will be best achieved through a combination of step-by-step explanations of key concepts -- grounded with real-world examples -- and "lab" sessions where students are asked to apply concepts towards a more complex problem in a guided environment. In terms of mentoring, I believe that each graduate student necessitates his or her own uniquely tailored mentoring strategy that requires periodic adjustments to fit the current needs. As a result, my approach will be more flexible, by design, in order to account for their individual needs. I believe weekly one-on-one meetings with students to discuss both research results and direction will not only provide a good way to learn about each student’s strengths, but also serve to highlight areas that could benefit from more guidance. Ultimately, my goal aims to help students build the proper fundamentals groundwork through helping them understand materials at a fundamental level and then training them to be proficient with the skills necessary to apply that fundamental knowledge to real-world problems.

Publications

1). Babji Srinivasan, Thi Vo, Yugang Zhang, Oleg Gang, Sanat Kumar, Venkat Venkatasubramanian. “Designing DNAgrafted particles that self-assemble into desired crystalline structures using the genetic algorithm.” PNAS, 2013, 110.

2). Thi Vo, Venkat Venkatasubramanian, Sanat Kumar, Babji Srinivasan, Suchetan Pal, Yugang Zhang, Oleg Gang. “Stoichiometric control of DNA-grafted colloid self-assembly.” PNAS, 2015, 112.

3). Yugang Zhang, Suchetan Pal, Babji Srinivasan, Thi Vo, Sanat Kumar, Oleg Gang. “Selective transformations between nanoparticle superlattices via the reprogramming of DNA-mediated interactions.” Nature Materials, 2015, 14.

4). Fang Lu, Thi Vo, Yugang Zhang, Alex Frenkel, Kevin G. Yager, Sanat Kumar, Oleg Gang. “Unusual Packing of Soft-Shelled Nanocubes,” Science Advances, 2019, 5. [co-first author]

5). Thi Vo and Sharon Glotzer. “Principle of corresponding states for hard polyhedron fluids,” Molecular Physics, 2019, 117.

6). Katherine C. Elbert, Thi Vo, Nadia M. Krook, William Zygmunt, Jungmi Park, Kevin G. Yager, Russell J. Composto, Sharon C. Glotzer. “Dendrimer ligand directed nanoplate assembly,” ACS Nano, 2019, 13. [co-first author]

7). Ye Tian, Julien Lhermitte, Lin Bai, Thi Vo, Huolin Xin, Ruipeng Li, Masafumi Fukuto, Kevin Yager, Sanat Kumar, Oleg Gang. “Ordered three-dimensional nanomaterials using DNA-prescribed and valence-controlled material voxels,” Nature Materials, 2020, 19.

8). Vyas Ramasubramani, Thi Vo, Joshua A. Anderson, Sharon C. Glotzer. “A mean-field approach to simulation anisotropic particles,” Journal of Chemical Physics, 2020, 153.

9). Katherine, C. Elbert, William Zygmunt, Thi Vo, Corbin M. Vera, Daniel J. Rosen, Nadia M. Krook, Sharon C. Glotzer, Christopher B. Murray. “Anisotropic nanocrystal shape and ligand design for co-Assembly through inverse design,” Science Advances, 2021, Accepted. [co-first author].