Dynamic Pathways & Feedback Control of Topological Defects on Topographical Surfaces

Johns Hopkins University, Baltimore MD

Investigators

Abstract

The goal of this project is to develop models to predict and describe the behavior for groups of particles, called colloidal assemblies, on curved surfaces. The behavior of interest is how the colloidal assemblies form different groupings and configurations called microstructures. By understanding the dynamics of how particle scale microstructures emerge on curved and deformable surfaces, real-time control will be developed for assembling particle-based surface structures with important and novel multifunctional properties. Practically, the aim is to assemble different shaped particles on different surface topographies to create synthetic materials that mimic natural materials as well as unnatural metasurfaces. Improving the control of these assemblies and resulting properties is expected to lead to techniques for fabricating these materials at a larger scale. Particle microstructures on curved surfaces will be targeted that exhibit novel properties (e.g., optical, electromagnetic, mechanical, wetting, etc.) essential to emerging technologies (e.g., optical coatings, solar cells, biomaterials, soft robotics, flexible electronics, responsive composites, etc.). To achieve these goals, microscopy and computer experiments will be used to understand and control mechanisms of non-equilibrium assembly of liquid crystal and crystal structures on curved surfaces including the role of curvature mediated packing defects. Broader impact activities will include educating a diverse and inclusive multidisciplinary workforce as well as outreach to underrepresented groups in Baltimore through classroom and laboratory modules involving microscopy and computational research visuals. The research plan includes a systematic series of connected aims to both gain fundamental understanding of dynamic pathways for assembly of different shaped particles on curved surfaces, and to enable feedback control of rapid microstructure evolution toward target states. In addition, the project aims are designed to address a central scientific hypothesis that different shaped particles on curved surfaces have different interactions, states, defects, and stochastic assembly, relaxation, and reconfiguration dynamics compared to particles on flat surfaces. In brief, the project aims are to: (1) obtain accurate high-dimensional particle scale dynamic simulations by matching potentials and diffusivities to microscopy experiments in a model material system with tunable potentials, (2) develop coarse-grained reaction coordinate based dynamic models, with pathway and rate information, for stochastic microstructure evolution in transient assembly processes including topological defect relaxation, and (3) implement feedback control with optimal control policies to achieve in minimum time low-defect target microstructures of different shaped particles in liquid crystalline and crystalline states on varying surface topographies. Achieving these aims will enable us to develop generalizable first principles models to control dynamic reversible assembly of different shaped particles into technologically useful ordered microstructures on curved surfaces. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.