Control of Microparticle Assembly
Xun Tang, Martha A. Grover
Abstract
A colloidal system is a large collection of micrometer-sized particles suspended in a liquid, and the state of the system can be measured in real time, using imaging techniques and image processing. The assembly of the particles is driven by interactions between the particles and the surrounding liquid, as well as by external fields, including electromagnetic, flow, and gravitational fields. The dynamics of the many-body system are high-dimensional, nonlinear, and stochastic. However, low-order models are derived in some cases, often using physics-based order parameters, to facilitate studying the system dynamics. With an understanding of the system dynamics, and by manipulating the aforementioned interactions, one can control the assembly process in real time using open-loop and closed-loop feedback control. Theoretical studies and experimental demonstrations of colloidal self-assembly control have been reported, with methods ranging from heuristic rules to model-based optimal feedback control.