(741b) Feedback Controlled Colloidal Crystal Assembly Via Electric Field and Depletion Mediated Interactions

The ability to assemble nano- and micro-sized components into ordered structures can serve as a basis for the scalable manufacture of meta-materials. However, a robust approach is not available to control the assembly of such structures due to the complexity of such processes and lack of available models. In this talk, we demonstrate the use of depletion and electric field mediated interactions in conjunction with free energy landscape (FEL) models to manipulate colloidal microstructures from fluid to crystal configurations. Externally applied electric fields and depletion induced via poly(N-isopropylacrylamide) (PNIPAM) hydrogel nanoparticles are used to tune kT-scale colloidal attraction via open- and closed-loop feedback control. The degree of colloidal crystallization is monitored using real-time particle tracking and order parameter computation. FELs are constructed using equilibrium (i.e. Boltzmann inversion) and non-equilibrium (i.e. fitting Smoluchowski equation coefficients) analyses of colloidal assembly trajectories. Our ability to directly measure and tune colloidal interactions, as well as model how these interactions affect dynamic colloidal microstructures, allows us to perform feedback control to manipulate the assembly, disassembly, and repair of colloidal crystals. These results provide a basis to produce perfect single colloidal crystals that can be translated to scalable manufacturing approaches.