High-aspect ratio polymeric pillar arrays formed via electrohydrodynamic patterning

This paper describes a method to increase the aspect ratio of polymeric pillar arrays formed by electrohydrodynamic instabilities. Pillar arrays form spontaneously across a narrow capacitor gap when an electric field is applied normal to a thin, fluidic film. This simple technique is appealing because of its ability to rapidly form arrays of small structures in an inexpensive manner. The columnar structures formed using this technique have low-aspect ratios, which are non-ideal for patterning applications. Theory suggests that stretching the structures post-formation is one of the only ways to increase the aspect ratio of the pillars. We developed a tool to physically stretch these structures to increase their aspect ratio from ∼0.1 to ∼0.5. The capabilities and limits of this stretching technique have been discussed.