Micro- and nanoxerography in liquids - controlling pattern definition

This article reports on directed self-assembly of particles onto locally charged surfaces via a xerography-like process. Particles are deposited in a parallel approach based on electrostatic fields generated by local surface charges in thin-film electret layers on a p-doped silicon support. Charge patterns are created with an atomic force microscope in lithography mode by applying voltage pulses between a conductive tip and the sample. Subsequently, the sample is developed in a water-in-oil emulsion, where the electrostatic field guides particle loaded water droplets through a nonpolar solvent to the previously defined patterns. Deposition characteristics onto poly (methyl methacrylate) and poly (tetrafluoro ethylene) substrates are examined for SiO2 and latex particles. Pattern resolution and definition are found to depend on the balance of Coulomb and dipolar forces. Not only the amount of charge deposited and charge pattern geometry influence this force balance, but also the material of the electret layer. (c) 2005 Elsevier B.V. All rights reserved.