Dynamics of the formation of polymeric microstructures induced by electrohydrodynamic instability

We perform two-dimensional simulations of an electrohydrodynamic patterning process for a mask-gap-polymer-substrate sandwich. The simulations help us identify the intrinsic pattern resulting from nonlinear interactions to be hexagonal when the mask is unpatterned, consistent with experimental observations. The dynamic evolution of the thin polymer layer under a patterned mask shows that the pillars start to form from corners, propagate along edges, and then grow inwards. This growth sequence, identical to experimental observations, creates a square pattern under a square mask, a hexagonal pattern under a triangular mask, etc. Besides the hexagonal pattern, simulations indicate the conditions under which various different patterns that have been observed in experiments should form.