Photocurable pillar arrays formed via AC- and ultrasound-induced electrohydrodynamic instabilities

摘要

Application of an external electric field across thin polymeric films is known to induce the formation of arrays of cylindrical structures commonly referred to as pillars. Low viscosity photocurable materials have been shown to possess significant advantages over their polymeric counterparts both in terms of a significant reduction in the time of formation, as well as in the elimination of additional processing steps, such as heating and cooling cycles. With proper design, pillar arrays with predetermined diameter, period, location and orientation can theoretically be formed over an entire substrate surface, thus enabling their use in applications such as optics-less patterning, micro-electro-mechanical systems, and micro fluidic devices. In this paper, we present our recent work in using a low viscosity thiolene system to produce pillar arrays and attempts at inducing long range order in the resulting pillar arrays by (1) varying the nature of the external electric field in the form of a sinusoidal AC voltage (instead of the conventional DC voltage) and (2) the use of ultrasonic piezo transducers to generate regular waves in the film with simultaneous application of a potential across the film sample. Our initial results show that although both the AC voltage and the ultrasonic piezo methods are successful in producing pillar arrays, their ordering is short-ranged and does not extend throughout the entire sample area.