(717e) Low-Dimensional Dynamic Models of Colloidal Cluster Assembly Using Tunable Electric Fields

Thyagarajan, R. - Presenter, University of Massachusetts Amherst
Maroudas, D., University of Massachusetts Amherst
Bevan, M. A., Johns Hopkins University
Ford, D., University of Massachusetts Amherst

Electric fields can be used to facilitate the assembly of small numbers (10-1000) of colloidal particles into ordered structures that may be employed as photonic crystals and other meta-materials. Control of such assembly processes in real time would be enhanced by the availability of low-dimensional dynamic models that accurately capture the particle-level physics. In this paper we describe the building of such models for a specific system: 210 silica particles of micron size in aqueous solution under the influence of a quadrupole field with adjustable voltage. We use a combination of Monte Carlo umbrella sampling and diffusion maps (DMaps) to identify the slow, low-dimensional manifolds in this system. The DMap coordinates are correlated against set of candidate order parameters (OPs) to identify a suitable choice of observables. We build Fokker-Planck (Smoluchowski) models in the chosen OPs and generate free energy and diffusivity landscapes at various voltage levels. Strategies for incorporating this information into real-time process control algorithms are also discussed.