Authors: N. Wu, L.F. Pease III and W.B. Russel
Affilation: Princeton University, United States
Pages: 743 - 746
Keywords: electrohydrodynamic patterning, instability
A polymer melt sandwiched with a gap fluid between two planner electrodes can self assemble into ordered microstructures under the influence of an electric field. Motivated by the variety of patterns observed in experiments, we perform a weakly nonlinear analysis to demonstrate that second and third order interactions among fastest growing Fourier modes favor hexagonal patterns under a featureless mask, in agreement with observations. Furthermore, two-dimensional simulations reveal that either hexagonally ordered pillars or holes can form in a bilayer system depending on the dielectric contrast, viscosity ratio, and relative thickness of the two layers. We construct a parametric map that distinguishes the conditions under which arrays of pillars and holes can form. We convert insights gained from these theoretical and numerical studies into the design of a “smart mask” to produce large scale alignment of ordered patterns over regions much greater in extent than their natural domain size. In this realization, narrow ridges that intersect to form regular patterns produce conformal square or triangular packings of pillars that preserve registry from one domain to the next. This first step toward engineering of electrohydrodynamic patterning over large areas facilitates various applications of this technology.