Coarse Grained Modeling & Control of Colloidal Assembly

Johns Hopkins University, Baltimore MD

Investigators

Abstract

The goal of the proposed project is to develop computational models of ensembles of differently shaped colloidal particles as a means to control their assembly into ordered microstructures with few defects. The proposed research may enable metamaterial applications involving micro-structured colloidal-based materials for manipulation of electromagnetic radiation. Example materials include novel reflectors, gratings, polarizers, waveguides, etc. as part of sensors, solar cells, antennas, optical computers, and cloaking devices, which all require periodic structures of different shaped particles with low defect densities. The focus of the research project will be on modeling and control of ellipsoidal and super-ellipsoidal particles to enable a rich set of microstructures. Novel methods for controlling interactions using directional and time varying inputs will be developed to enable precise control of colloidal particle assembly processes. Understanding the thermodynamics and kinetics in colloidal systems is challenging and applying feedback control adds an additional layer to engineering complex responses in such systems. The goal of the proposed research is to develop minimal physically-meaningful models of stochastic dynamics to design model-based feedback control policies for the assembly of ellipsoidal and super-ellipsoidal particles. The objective is to significantly adapt and extend prior approaches to systematically define coarse grained system coordinates that capture structural features while eliminating system symmetries. The feedback control policies will be tested experimentally with tunable kT-scale interactions to design dynamic reversible assembly of different shaped particles into ordered metamaterials. The fundamental understanding of design rules and control parameters for colloidal assembly will provide new general insights beyond what is known from trial-and-error discovery. The project will train students by integrating broad topics in colloid science, fluid dynamics, materials chemistry, advanced metrology/microfabrication, and control. Broadening participation of underrepresented groups in STEM fields will be pursued through weekly mentoring activities at a local elementary after-school program focused on engineering design. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.