Photothermal Surface Plasmon Resonance and Interband Transition-Enhanced Nanocomposite Hydrogel Actuators with Hand-Like Dynamic Manipulation

Hydrogel actuators represent a powerful tool due to their ability to capture, move, and be manipulated, which has applications in diverse fields. The development of hydrogel actuators capable of localized movement, where only a part of the whole system moves, wireless remote control, and flexible shape-changing is critical and challenging to fulfill their potential. Here, photothermal hydrogel actuators are designed and fabricated to accomplish a precise hand-like manipulation of encapsulating and finger-like one-by-one bending by light. A thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) active layer and a non-thermoresponsive poly(acrylamide) passive layer are combined to generate a thermal-expansion coefficient mismatch among the interface and this energy eventually transforms into a bending motion. As an energy transformation agent, the gold nanoparticles doped in the PNIPAm hydrogel absorb the light energy and transform it into thermalenergy effectively as a result of a surface plasmon resonance electron-phonon process and intrinsic interband transitions. The resulting nanocomposite actuators exhibit flexible, reversible motions and local hand-like finger flexion driven by either flood illumination or local irradiation. The developed programmable actuators are expected to be an attractive candidate for the next generation of smart soft robots.