Colloidal Interactions, Structure, and Dynamics on Curvature Landscapes

About This Grant

Non-technical abstract: The vast majority of surfaces of any origin (biological, geological, synthetic) are not flat, smooth, and rigid but instead are generally curved, rough, and deformable, particularly for soft materials. Particle micro-structures formed on such curved surfaces through coating technologies can be used to control many of their interfacial material properties (optical, mechanical, thermal, porosity, etc.). However, particles pack differently on curved surfaces than flat surfaces, which can affect the resulting micro-structures and their ultimate properties in important applications such as two- and three- dimensional printing, optical coatings, flexible electronics, energy capture and storage, and membranes for chemical separations. This project will use optical microscopy and computer experiments to investigate how different shaped particles interact and move around on curved surfaces as part of assembling different surface microstructures with technologically useful properties. The intellectual merit of this project will result from new basic understanding of how different shaped particles assemble into a variety of micro-structures on various curved surface shapes (spherical, cylindrical, wavy). Broader impacts of this project will include educating a multidisciplinary workforce as well as outreach to pre-college level students through classroom and laboratory modules involving microscopy and computational research visuals. Technical abstract: The overall goal of this project is to understand the connection between interactions, structures, and dynamics for spherical and ellipsoidal colloidal particles on curved surfaces. A central hypothesis of the project is that topological defects due to geometric frustration will significantly alter mechanisms relating colloidal interactions, structure, and dynamics on curved surfaces compared to flat surfaces. To understand how near-equilibrium colloidal microstructure and dynamics depend on tunable potentials, particle shape, and curvature landscape features, the proposed project will involve closely coupled optical microscopy and computer simulation experiments. The proposed research plan has systematic interconnected aims with step-wise increasing complexity, including measuring and modelling: (aim1) interactions of spherical and ellipsoidal colloidal particles on curved surfaces vs. particle aspect ratio, surface coverage, and substrate curvature, (aim2) interfacial particle structures on curved surfaces including spatial density variations, order parameter profiles, and topological defect type and spatial arrangements, (aim3) translational and rotational self-diffusion and defect dynamics within curvature dependent states including dynamical heterogeneity relative to topological defects. Achieving these aims and overall goal will provide fundamental understanding of how curvature dependent particle scale mechanisms link interactions, microstructural states, topological defects, and diffusive dynamics at near equilibrium conditions, which will provide a basis for future studies of transient microstructure evolution and ultimately formal design and control of such processes. 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.