Direct formation of high aspect ratio multiple tilted micropillar array in liquid phase PDMS by proton beam writing

Abstract

High aspect ratio (HAR), straight and tilted micropillars were fabricated in PDMS polymer by proton beam writing (PBW) method. The polymer was applied as a negative tone resist material, in its liquid and high viscosity form. The microstructures were created by irradiating the polymer with 2MeV focused proton beam, by which, the irradiated area became cross-linked and solid. The formed micropillars had very smooth side walls and they were stable against the capillary and adhesion forces, above a certain applied proton fluence. The rate of the solidification strongly depends on the deposited ion fluence. Furthermore, some physicochemical properties, such as elastic modulus also significantly change due to ion irradiation induced processes. This liquid PDMS resist with PBW makes the possibility to create high aspect ratio, straight or even tilted micropillar arrays with tunable properties, which can be useful in many potential applications, like lab-on-a-chip devices, high surface required applications, catalysis, biomedical applications, cell separation, and directional adhesive surfaces.