Toward Light-Responsive Hydrogel-Based Valves for Flow Regulation.

Smart hydrogels are promising materials for soft actuators in biomedical applications thanks to their varied responses to external stimuli. Light is a particularly attractive trigger for contactless stimulation of hydrogels that can induce reversible morphological changes without damaging the fragile gels. To meet the varied needs of applications in microfluidics, soft robotics, biomedicine, and other fields, there is significant demand for novel valve designs that are highly tunable, miniaturizable, and respond quickly to stimuli while maintaining their function over many activation cycles. Additionally, it is crucial to develop a more quantitative understanding of the mechanics of valve operation in response to different stimuli, especially when active hydrogels are combined with other materials in multicomponent devices. Here, stimulus-responsive valves are fabricated using active hydrogels deformed upon temperature changes and exposure to near-infrared radiation. Gold nanorods (AuNRs) acting as photothermal transducers are embedded inside cross-linked poly