Generation of sidewall patterns in microchannels via strain-recovery deformations of polystyrene

In this work we have developed a simple approach to generate micropatterns on the sidewalls of polystyrene (PS) microchannels. The PS used is a thermal shape-memory polymer. The sidewall patterns were produced based on large strain-recovery property of this polymer. During the strain recovery, a shallow, wide channel became a deep, narrow channel. In the meanwhile, micropatterns that pre-existed on the slightly sloped sidewalls of the shallow channels were transferred to approximately vertically oriented sidewalls of the deep channels. A simple mathematical relationship was proposed to determine the new orientations of the channel sidewalls after the strain recovery. This relationship was further validated by experiments. The developed approach has been successfully applied to generate Ag 50 μm × 50 μm dots, 100- and 500 μm-wide straight lines, and 150 μm-wide serpentine lines not only on the bottoms but also on the sidewalls of PS microchannels. Furthermore, the generation of a simple conductor across a channel was explored. This conductor included external wires, contact pads and Ag lines. The fabricated conductor could be potentially applied to create a 3-D electrical field inside the channel.