Fabrication of poly(dimethylsiloxane) concave microlens arrays by selective wetting and replica moulding

This Letter describes a novel approach in fabricating poly(dimethylsiloxane) (PDMS) concave microlens arrays (MLAs) by using a combination of microcontact printing (μCP), selective wetting/dewetting and replica moulding. μCP is used to generate a chemical pattern utilising hexadecanethiol (HDT) as an ink on gold substrate. When polyethylene glycol (PEG) is dip-coated on the chemical pattern, the PEG solution selectively dewets the HDT patterned regions and wets the remaining bare gold regions, resulting in the formation of a PEG dot array. Then, PDMS concave MLAs were fabricated by replica moulding of the PEG dot array. The fabricated microlenses have a diameter of 39.9 μm and a sag height of 2.9 μm as were revealed by a scanning electron microscope and atomic force microscopy. This method provides a simple and low-cost approach to prepare large-area PDMS concave MLAs, which has potential application in many optoelectronic devices.