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Electrostatic Crystallization in Shaken Granular Systems

Stoyan K. Smoukov1, Yuriy Chegel2, and Bartosz A. Grzybowski1. (1) Chemical & Biological Engineering, Northwestern University, 2145 Sheridan Rd/TECH E136, Evanston, IL 60208, (2) Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Ave., Tech E-136, Evanston, IL 60208

Granular mixing displays complex phenomena even in the absence of strong interactions between particles. Often special care is taken to minimize such interactions in order to study the systems. Electrostatic interactions often arize due to contact electrification in agitated granular systems. They are the main reason that systems with particles < 100 microns are rarely studied. In order to understand electrostatic-based interactions in granular systems, two-dimensional crystallization is studied in a system of 1mm-sized polymer balls charging to two opposite charges. The intermediate structures are observed and the transition to crystal structures is quantified using correlation functions. Major forces acting on the particles are identified, as well as parameters for optimal crystallization.