Rewritable microrelief formation on photoresponsive hydrogel layers

The quick photoresponse of thin hydrogel layers composed of thermoresponsive poly(N-isopropylacrylamide) (pNIPAAm) with an acrylated SP chromophore incorporated in the polymer backbone were analyzed. Drastic photoinduced volume change of the hydrogel was examined, and the instant formation of microrelief on a thin hydrogel layer was demonstrated by means of micropatterned light irradiation. The hydrogel layer was irradiated with blue light to quantitatively analyze the photoinduced change in the surface profile. After the light irradiation, the thickness change of the hydrogel layer was evaluated as a function of time. Results showed that micrometer-scale microrelief with a high aspect ratio can be formed instantly on a thin hydrogel layer composed of thermoresponsive pNIPAAm and photoresponsive spirobenzopyran by irradiating with blue light. It was observed that the charge density is substantially reduced as a consequence of light irradiation.