Electrokinetic concentration, patterning, and sorting of colloids with thin film heaters.

Reliable and simple techniques for rapid assembly and patterning of colloid architectures advance the discovery and implementation of such nanomaterials. This work demonstrates rapid electrokinetic two-dimensional assembly of colloidal structures guided by the geometry of thin film heaters within a parallel-plate device. This system is designed to enable either independently addressable or massively parallel colloidal assembly. A combination of electrothermal hydrodynamics, particle-electrode, and particle-particle electrokinetic interactions governs their assembly. Concentration and patterning of structures are shown with 1.0 μm polystyrene particles and sorting between 1.0 μm and 2.0 μm particles is demonstrated.