Environment-friendly photolithography using poly(N-isopropylacrylamide)-based thermoresponsive photoresists

We report a novel approach for the temperature-triggered development of water-soluble photoresists based on photocleavable poly(N-isopropylacrylamide) copolymers. These copolymers are soluble in an aqueous environment below their Lower Critical Solution Temperature (LCST). Upon UV irradiation, the photocleavable groups are deprotected resulting in an increased LCST. Thus, the illuminated parts of spin-coated copolymer layers dissolve at higher temperatures than the surrounding areas, leading to pattern development. The photoresist can finally be completely removed at low temperature. We demonstrate the applicability of this novel photolithographic approach by the patterning of fluorescent proteins.