A polyvinyl alcohol microlens array with controlled curvature on discontinuous hydrophobic surface

Abstract

In this paper, a facial method was used to fabricate polyvinyl alcohol (PVA) microlens arrays (MLAs) with controllable focal lengths on discontinuous hydrophobic surfaces. To this end, a hydrophobic materials-based solution was spin-coated onto the patterned photoresist surface. After solvent evaporation, a discontinuous hydrophobic surface was obtained by removal of the photoresist. The as-obtained microhole patterned hydrophobic layer modified substrate exhibited hydrophilic and hydrophobic properties inside and outside the microholes, respectively. The scribing of PVA solution allowed its adherence to the hydrophilic area to form a droplet self-assembly due to surface tension. PVA MLAs with radii of 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm were obtained to demonstrate the suitability of the proposed method. The curvature of MLAs can be adjusted by controlling the volume of PVA solution in the microholes or changing their sizes. In sum, the proposed PVA MLAs with high optical performances, easy fabrication, and good mechanical properties look promising for future applications in image processing, light extraction, protein detection, light-emitting diodes, sensors, and displays.