Morphology-controlled two-dimensional elliptical hemisphere arrays fabricated by a colloidal crystal based micromolding method

In this paper, we demonstrate a facile modified micromolding method to fabricate morphology-controlled elliptical hemisphere arrays (EHAs) by using stretched poly(dimethylsiloxane) (PDMS) nanowell arrays as molds. The PDMS nanowell arrays were fabricated via casting PDMS prepolymer onto two-dimensional (2D) non-close-packed (ncp) colloidal sphere arrays. By varying the stretching direction, stretching force, size of the colloidal spheres used and other experimental conditions in the fabrication process, we can control the shape, aspect ratio and size of the resulting microstructures. Moreover, our method does not involve any costly micromanufacture technique and can be applied to a great many materials, such as oil soluble polymers (e.g. polystyrene (PS)), water soluble polymers (e.g. poly(vinyl pyrrolidone) (PVP)), cross-linked polymers (e.g. photopolymerizable resin) and a variety of composites (e.g. polymer/nanoparticle composite). The anisotropic wetting properties of these EHAs were demonstrated. Potential application of the EHAs is to provide a model for the fundamental research of anisotropic surfaces and a template or mask for the fabrication of anisotropic surface patterns for potential applications of shape-dependent optical and magnetic devices.