Colloids Painted Black and White: Rotational Diffusion of MOON particles Steve Granick, Dept. of Materials Science and Engineering, University of Illinois Petroleum relevance and novelty: Colloidal particles in 4 dimensions: rotation, in addition to the classical interest in spatial position. The grand challenge is to develop molecular colloids that self-assemble by orientation-dependent interaction analogous to chemical bonds. We aim to develop molecular colloids that self-assemble by orientation-dependent interaction analogous to chemical and physical bonds. Progress this year concerns: new single-particle tracking algorithms to quantify rotational diffusion quantification of structures formed by bipolar particles, in cooperation with Monte Carlo simulations by Prof. Erik Luijten (see figure). These micron-sized particles are positive on one hemisphere, negative on the other, and overall neutral in charge. Their clusters are under investigation. Enabling idea: Newly-developed methods and algorithms for single-particle imaging.