Two-Dimensional Pre-Assembled Multi-Scale Brownian Soft Matter

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Nontechnical Abstract:Some pure materials are highly uniform and have essentially the same structure and properties from very small to very large length scales. However, other materials, including biological tissues, have different structures and properties at different length scales from microscopic to macroscopic; these are 'multi-scale' materials. One of the most important current challenges in physical science involves developing rules that describe increasingly complex multi-scale materials which begin to approach the extremely high level of complexity found in biology. This project focuses on creating and studying the behavior of highly contollable synthetic multi-scale materials that contain moving shape-designed particulate components dispersed in a liquid. Optical lithography, which is the key technology for mass-producing computer chips, enables the top-down production of human-designed, pre-configured, multi-scale materials composed of mobile tile-like particles that have interesting shapes and arrangements at different length scales in two dimensions. Beyond revealing physical rules that govern the dynamics and structures of mobile constituents and coupling between different length scales in such multi-scale materials using optical microscopy, this project benefits K-12 students, including underrepresented minority students, in the Los Angeles area by introducing them to the basic concepts of lithography through age-appropriate educational modules that are deployed in conjunction with educators-in-training at UCLA's Center X.Technical Abstract:The recent advent of lithographically pre-assembled monolayers of mobile shape-designed colloidal tiles, made using optical stepper lithography, provides a new and powerful experimental route for making two-dimensional dynamic systems having controllable multi-scale complexity. This project takes advantage of lithographically pre-assembled monolayers to explore both equilibrium and non-equilibrium multi-scale materials, including quasi-crystals and hierarchical crystals-of-crystals, that have controlled symmetries and topologies spanning a wide range of length scales. Time-lapse optical video microscopy experiments of these systems yield spatio-temporal kinetics and dynamics down to the tile scale, thereby yielding measurements of the fluctuations and evolution of shape-designed monolayer systems both as a consequence of entropic Brownian excitations and also as a consequence of active driving. From particle tracking analysis of these videos, quantitative insight into multi-scale complex systems of crowded shapes serves as a starting point for understanding more complex forms of active and biological matter.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.