RUI: Self-Organization and Memory in Disordered Materials

Non-Technical Abstract

Many materials and systems are driven repeatedly: buildings and bridges are repeatedly loaded and unloaded, temperatures change between day and night, and many skills are learned only through recurring practice. After many such repetitions, a system may have formed a specific 'memory' of the driving that will directly influence its future behavior. The principal investigator and students perform experiments on two physical systems that are very likely to form memories in this way: a two-dimensional version of a solid material, and the boundary between wet and dry regions on a rough, flat surface. The goal of this project is to develop new ideas about memory formation generally, both as a way to program the behavior of matter, and as a way to compare and contrast materials at a fundamental level. The project involves undergraduate students who carry out most of the experiments and the computer analysis of the resulting large data sets, developing in-demand skills and gaining experience working at the research frontier. This project also creates additional laboratory experiences, public outreach opportunities, and professional development opportunities for a broader array of Cal Poly students.

Technical Abstract

This project studies how disordered systems and materials self-organize and evolve under repeated cyclic driving, and may form memories of that driving. The project involves experiments on two systems: a sheared 2D disordered solid formed by colloidal particles adsorbed at an oil-water interface; and the interface between two fluids (e.g. water and air) inside a roughened channel, in which the pinned contact line evolves as fluid is injected and withdrawn. In both experiments the PI and students apply many cycles of driving, making microscopic and mechanical observations to test how these systems are changed and programmed by the driving. The main goal is to test and develop the idea that there exist generic classes of memory behavior. Specifically, the two experimental systems feature comparable yielding and depinning transitions, and so are an opportunity to connect common physics to a common class of memory. The PI's main goal is a deeper understanding of how processing and environment can program the structure and behavior of matter. Undergraduate students play an integral role in experiments and analysis, and as part of this project the PI creates additional laboratory experiences, public outreach opportunities, and professional development opportunities for a broader array of Cal Poly students.