Numerical studies of electrically induced pattern formation by coupling liquid dielectrophoresis and two-phase flow

Abstract

Electrically induced patterning process, as a novel micro- or nano-structuring approach for fabrication of various micro- or nano-systems, is usually implemented by applying a voltage to an electrode pair consisting of a patterned or non-patterned template and a polymer-coated substrate separated in parallel by an air gap, followed by photo- or thermo-curing of the fluidic and dielectric polymer. The analyses performed so far to characterize this patterning process have been based on linear thermodynamics for a thermally instable thin film perturbed by an electrostatically induced hydraulic pressure. For mathematical simplicity, these analyses were formulated only for a flat template and a flat film surface with infinite planar area, demonstrating the tendency of initial pattern growth on the polymer film, but being unable to visualize the dynamic evolution of micro- or nano-structure growth throughout the patterning process for a real-life template in practical applications. This paper attempts to provide another insight into this patterning process from a viewpoint of liquid dielectrophoresis (L-DEP), by presenting an approach for numerical simulation of the patterning process based on a coupling of L-DEP and two-phase flow theories. First, a numerical analysis has been made for the electrocoalescence of a water droplet with bottom water in silicone oil to benchmark effectiveness of the proposed numerical approach against published experimental observations. More numerical results have then been provided to show effects of some process variables on the evolution of the polymer micro- or nano-structures for this patterning process.