Controllable assembly and disassembly of high aspect ratio micropillar arrays and their applications
Date of Issue2017
School of Materials Science and Engineering
Flexible materials PDMS has been fabricated into different kinds of structures and contributed to the materials science and engineering area. Due to its easy-to-fabricate nature, many shapes had been designed to fit the need of applications. Among them, micropillar arrays are important for many applications, including cellular mechanosensory and actuators, dry adhesives mimicking gecko’s foot structures and optical applications such as ultrathin paper whitening membranes. And as the surface area is relatively large and aspect ratio is high, the micropillars will deform under minuscule external forces such as capillary force when liquids evaporated from the micropillar surfaces. Previously researchers had developed many applications from this unique property and studied the mechanism of micropillar assembly under capillary force. However, it lacked in-depth understanding in the deformation process. In this thesis, we had systematically studied the controlling factors of micropillar array assembly, including pattern geometry, and surface chemistry. Besides, mathematic models had been built to predict the pillar assembly patterns by calculation. We studied the micropillar deformation under capillary force both theoretically and experimentally. And we created a series of assembled micropillar patterns that can trap bacteria and microparticles based on their size. Moreover, we successfully developed a hydrogel coated PDMS micropillar array structure. It was responsive to dual stimuli, mechanical stretch, and pH changes and controllably release the trapped microparticles. These devices had potential to be applied in live bacteria capture for drug screening devices, and mechanical force triggered pH-responsive controlled drug release devices.