Programmable Photothermal Hydrogel Actuators Enabled by Adhesion

ABSTRACT Stimuli‐responsive hydrogels are promising for soft actuators, with thermoresponsive systems widely explored. Photothermal actuation, driven by light‐induced localized heating, offers new possibilities, but conventional bilayer fabrication methods remain complex and time‐consuming. Here, we present a simple, one‐step approach for constructing bilayer photothermal actuators by directly bonding conductive polymer films to thermoresponsive hydrogels via electrophoretic adhesion. A negatively charged poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS) film is adhered to a cationic poly( N ‐isopropylacrylamide) (PNIPAAm) hydrogel under an electric field, forming a robust polyion complex interface. The resulting bilayers exhibit strong adhesion in aqueous environments and achieve 90° bending within 5 s under near‐infrared (808 nm) irradiation. Photothermal heating of PEDOT/PSS elevates local temperature above PNIPAAm's lower critical solution temperature, inducing shrinkage and bending toward the hydrogel side. Actuation amplitude scales with laser intensity, and repeated cycles maintain performance without delamination. Patterned adhesion enables programmable deformation, including localized bending, S‐shaped motion, and helical twisting, demonstrating precise spatial control. This washing‐free process overcomes limitations of sequential polymerization and provides a versatile platform for reconfigurable hydrogel actuators, with potential applications in soft robotics, adaptive devices, and biomedical systems.