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This paper presents rapid photothermal actuation of light-addressable, arrayed hydrogel columns in a macroporous silicon membrane. Au nanorods are incorporated into thermo-responsive p-NIPAAm hydrogel to utilize surface plasmon-induced local heating by near-infrared light. By measuring optical transmission through the fabricated membrane structure with Au nanorod embedded hydrogel, we have demonstrated that photothermal actuation of hydrogel can be done in two-dimensional, pixel-like configuration with high spatial and temporal resolutions. Benefiting from the hydrogel volume confinement within micron-sized pores, we have achieved sub-second response time of hydrogel photothermal actuation and its repeatable photothermal actuation on highly localized illuminated area. Considering that each hydrogel column is confined within each pore and different wavelength of light can be used to induce photothermal actuation of hydrogel's deswelling characteristics by modifying physical dimensions of Au nanorods, it has a potential for optically-addressable, multiplexed drug release systems with rapid response time.

We have fabricated a temperature-sensitive hydrogel through copolymerization of N-isopropylacrylamide (NIPAAm) and Acrylamide (AAm) inside a macroporous silicon structure and demonstrated fast thermal response compared to its bulk structure. The presented method allows physical arrangement of micro-sized hydrogels within a predefined arrayed structure. Static and dynamic temperature responses of the fabricated structure are successfully demonstrated through optical transmission measurement. The measured temporal response reveals that presented structure can allow fast response time of the implemented hydrogels. Furthermore, spatial thermo-distribution pattern can be observed through pixel-like, arrayed macropores, which indicates a potential for addressing individual or single-channel hydrogel sensors or actuators through temperature stimulation.

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