NIR responsive and conductive PNIPAM/PANI nanocomposite hydrogels with high stretchability for self-sensing actuators

Integration of mechanical and actuation properties with sensory feedback function in soft actuators remains a challenge. Herein, a highly stretchable and electrically conductive hydrogel with fast stimuli-responsive actuating performance is prepared by in situ growth of polyaniline (PANI) nanoparticles in the Pluronic F127 diacrylate (F127DA) cross-linked poly(N-isopropyl acrylamide) (PNIPAM) hydrogel matrix. The obtained PNIPAM/PANI hydrogel exhibits high stretchability (730%) and fast deswelling properties upon heating. Taking advantage of highly efficient photothermal conversion of the embedding PANI, this hydrogel shows a significant temperature rise of ∼50 °C within 150 s and large volume shrinkage of 65% upon near-infrared (NIR) light irradiation. Accordingly, the hydrogel is explored as an underwater actuator, which has achieved programmable deformations to simulate hand-like gestures and Venus flytrap-type locomotion under local NIR irradiation. In addition, the hydrogel is able to translate the local strain into electrical signals. The light-triggered actuation, including bending, weight lifting and moving objects can be monitored by real-time resistance change. These results confirm that actuating and real-time sensory feedback could be integrated in a single homogeneous material, which make it an outstanding candidate in soft actuators and even intelligent biomimetic devices.