Size-dependent planar colloidal crystals guided by alternating electric field

The authors demonstrate that two-dimensional crystals can be assembled from suspensions of colloidal spheres subjected to an alternating electric field on the surface of electrodes. The order parameters of monolayer colloidal crystals, which are extracted from the translational correlation function g(r) and bond-orientational correlation function g(6)(r), are employed to quantitatively characterize the ordering of the colloidal assemblies. This method has been applied on colloidal spheres of various sizes ranging from 450 nm to 5.0 mu m. In particular, high-quality crystals of spheres sized differently are controlled by different domains of frequency. This technique could be a rational method to assemble micro- or submicron colloidal spheres. (c) 2007 American Institute of Physics.