Fabrication of microstructures using shrinkable polystyrene films

Abstract This paper demonstrates the combination of reactive ion etching (RIE) and shrinkable polystyrene (PS) films to reduce the feature size of microstructures and to generate microstructures with high aspect ratios on both planar and curved surfaces. A shrinkable PS film is patterned with relief structures using RIE through a physical mask. The patterned surface is heated and shrinks. After shrinking, the size of microstructures decreases by a factor of four to five, and their height increases by a factor of ∼ 20. Thermal shrinkage results in a 100-fold increase in the aspect ratio of the patterned microstructures in the PS film. Microstructures as high as ∼ 126 μm with aspect ratio of ∼9.5 have been generated. The smallest structures fabricated using this strategy are rectangular pits ∼ 1.4 μm × 1.7 μm in size. Fabrication of microstructures on curved surfaces has been demonstrated by folding a patterned PS film and allowing it to shrink in place.