Optically induced electrohydrodynamic instability-based micro-patterning of fluidic thin films

Projected light patterns are used to induce electrohydrodynamic instabilities in a polymer thin film sandwiched between two electrodes. Using this optically induced electrohydrodynamic instability (OEHI) phenomenon, we have successfully demonstrated rapid, microscale patterning of polydimethylsiloxane (PDMS) pillar arrays on a thin-film hydrogenated amorphous silicon layer on top of an indium titanium oxide glass substrate. This glass substrate is the bottom electrode in a two-electrode, parallel-plate capacitor configuration with a micron-scale gap. Within this gap are a thin film of spin-coated PDMS and a thin layer of air. Primary pillar growth is first observed within 5-90 s in the dark regions of the projected patterns and pillar growth eventually spreads to the illuminated regions when the initial PDMS thickness is