MSE Seminar: Gregory Grason (UMass Amherst)
Geometrically-programmable assembly of self-limiting material structures
Living systems make a variety of functional and remarkably adaptive material structures via assembly of highly complex, nanoscale protein “building blocks”. Many of these assembled architectures, from viral capsid shells to multi-filament extracellular protein fibers, have well-defined and finite sizes, and moreover, their functional properties (e.g. transport mediation, mechanics) rely on specific control of that finite size. Notably this class “self-limiting” assembly is distinct from almost all types of synthetic self-assembled materials, which often target well-defined and complex local structures, such as crystals, but exhibit unregulated, if not unlimited, dimensions at the large scale. In this talk, I discuss recent progress in understanding and engineering self-limiting assemblies, in which the equilibrium dimensions of complex material structure are encoded in complex building blocks from which they assemble. This is motivated both by aspirational examples of finite-size, functional assemblies in biology, but also new classes of programmable particles that incorporate many key features of protein-like assembly (e.g. lock-and-key type “specific” interactions and geometrically-defined subunit shapes). I will discuss combined experimental and theoretical studies of a basic mechanism of self-closing, curvature-controlled assembly of a range of bioinspired capsules, tubules and bicontinuous structures, which reveal fundamental trade-offs between design economy and selectivity of target structures. Finally, I will highlight ongoing efforts to understand and realize size-control through new mechanisms of frustration-controlled assembly, in which finite dimensions of self-assembled structures can be programmed via “engineered misfits” between self-assembled subunits.
Bio:
Greg Grason is a professor of polymer science and engineering at University of Massachusetts Amherst, where he is also an adjunct professor of physics. He received a Ph.D. in physics from the University of Pennsylvania in 2005. Following a postdoctoral position in the Department of Physics and Astronomy at UCLA, he joined the faculty of UMass in 2007. His research investigates the role of geometric frustration in soft matter and polymeric assemblies through the combined lens of condensed matter theory, statistical physics and geometry. Recent efforts have focused on complex morphology and response in filamentous assemblies and membranes, hierarchical order in block copolymer assemblies, physics of frustrated, soft matter and programmable self-assembly. He is an Editorial Board Member of the New Journal of Physics and Giant and was elected Research Fellow of the Alfred P. Sloan Foundation (2011) and Fellow of the American Physical Society (2019).