Light-driven flow control in the hydrogel microchannel by utilizing a metal microstructure fabricated by multiphoton photoreduction

The light-stimulated control of flow velocity in the hydrogel microchannel was demonstrated by utilizing a metal microstructure fabricated by multiphoton photoreduction. The metal microstructure was fabricated adjacent to the microchannel in a poly-N- isopropylacrylamide (PNIPAm) hydrogel. Owing to the photothermal conversion at the metal microstructure, local deformation of the microchannel and change in flow velocity was induced as a result of the volume phase transition of the supporting hydrogel around the metal microstructure. Wavelength-selective change in the flow velocity was realized by utilizing dissimilar metal microstructures, that exhibit different optical resonances. The results indicate that multiphoton photoreduction is a promising method for fabricating novel hydrogel devices having flow-controllable switches by arranging light-absorbing structures with high spatial selectivity.