(634c) Electric-Field Induced Assembly of Nematic Order in Colloidal Rods

Colloidal particles with anisotropy in shape and interactions offer possibility for the assembly of colloidal crystals with unusual structure and symmetry. Field-assisted assembly is likewise a means to form structures that are difficult to access by simple self-assembly. In this work we report the use of an applied DC electric field to produce anisotropic orientational order in micron-sized Brownian colloidal rods. We report the effect of applied electric field strength on orientational order in suspensions of the rods with aspect ratio between about three and eight. The structure of these assemblies is imaged in 3-D using confocal microscopy. We use image-processing algorithms to identify the orientation and position of the all the rods in the assembled structure. We connect our results to the equilibrium isotropic-nematic transition predicted for hard rods and also discuss the observation of glassy dynamics observed at high-applied electric field strengths.