Colloidal assembly and 3D shaping by dielectrophoretic confinement.

For decades, scientists and engineers have strived to design means of assembling colloids into ordered structures. By now, the literature is quite peppered with reports of colloidal assemblies. However, the available methods can assemble only a narrow range of structures or are applicable to specific types of colloids. There are still only few generic methods that would lead to arbitrary colloidal arrays or would shape colloidal assemblies into predesigned structures. Here, we first discuss in detail how to spatially control the assembly and crystallization of colloids through the balance of dielectrophoretic and dipolar forces. Furthermore, we demonstrate how to flexibly program and shape arrays of 3D microstructures that can be permanently affixed by in situ UV polymerization and calcination by using two facing similar or distinct micro-fabricated electrodes.