(565g) The Response of an Anisotropic Colloid to a Nearby DC Electrode

For nearly thirty years, the directed assembly of colloidal particles proximate to an electrode has been studied in an effort to design a bottom-up process for the synthesis of two-dimensional colloidal crystals. More recently, work in this area has shifted from studying isotropic particles (with directionally independent properties) to studying the response of anisotropic particles (with directionally dependent properties). In principle, colloidal assemblies fabricated from anisotropic particles will have more complex microstructure than those fabricated from isotropic particles, which tend to form only close-packed arrays. This presentation will focus on the specific case of a geometrically anisotropic dielectric particle with non-uniform zeta potential responding to a nearby dc electrode. A numerical solution was obtained for the electric and flow fields in the proximity of the particle. Equilibrium charge electroosmotic (ECEO) flow is generated along the surface of the particle at these conditions, with the strength and direction of the flow depending on the magnitude and sign of the particle’s zeta potential. Results from the numerical solution indicated that the ECEO flow field and the accompanying interparticle interactions were anisotropic. In addition, a net lateral force acted on the particle perpendicular to the dc electric field, which is very similar to induced charge phenomena experienced by a metallo-dielectric Janus particle in response to an electric field. The origin of this force is the asymmetry of the ECEO flow field, which can be tuned by tailoring the shape and surface chemistry of the particle.