Pushkar Lele and Eric M. Furst. University of Delaware, Newark, DE
We use AC electric fields to drive the assembly of colloidal particles. Low frequency electric fields are known to enhance dipole-dipole interactions between particles through the double layer polarization. However, at short distances, the overlap of the double layers leads to band formation within the suspension through an anomalous rotation of the particle doublets. We work in optimum frequencies and field strengths based on our phase map for order (chaining) to disorder (bands and vortices) transition, and direct the ordering of these particles using templates generated by the holographic tweezers. Such a combination of optical and electric fields provides an exciting opportunity to create reversible patterned arrays of particles in discrete locations.