Synergistically crosslinked P(NIPAM-AM)/TA-Fe3+/CS composite hydrogel enabling NIR-driven actuation and resistive self‑sensing

P(NIPAM-AM)/CS/TA-Fe 3+ hydrogel integrates NIR actuation and self-sensing. • Optimized network enables a 4.7 s fast response and 104° maximum bending. • TA-Fe 3+ coordination offers a high photothermal conversion efficiency of 27.76%. • Linear resistance-strain mapping predicts bending angles with ≤ 2.67% error. • The dual-function material allows real-time feedback for closed-loop control. Conventional hydrogel actuators often suffer from single functionality and a lack of real-time state feedback, restricting their potential in closed-loop control and intelligent applications. To address this, we designed a synergistically crosslinked composite hydrogel based on poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-AM)), tannic acid-iron ion (TA-Fe 3+ ) complexes, and chitosan (CS). This hydrogel integrates near‑infrared (NIR)‑driven actuation with resistive self‑sensing and exhibits excellent shape programming and multidirectional actuation capabilities. By systematically optimizing the composition, the hydrogel with 0.1 mL of CS solution achieves a rapid response time of only 4.7 s and a maximum bending angle of 104°. Furthermore, at an Fe 3+ content of 120 mg, the hydrogel demonstrates a high photothermal conversion efficiency of 27.76% and an initial conductivity of 2.549 (Ω·m) −1 . It exhibits excellent self-sensing characteristics, with a bending gauge factor of 0.019 and high angle-sensing accuracy with an error of ≤ 2.67%. This work provides a simple and efficient strategy for developing intelligent soft materials that integrate actuation and sensing. Download: Download high-res image (220KB) Download: Download full-size image