Bioinspired MXene-Polymer Actuators with “Two-Way Traffic” and Positive Feedback Loops

The development of soft actuators capable of large, reversible deformation under multiple stimuli is crucial for next-generation intelligent and bioinspired systems. However, most reported multistimulus actuators rely on the simple superposition of independent driving mechanisms, lacking true coupling or synergy. Here, we report a biomimetic “two-way traffic” MXene–polymer actuator that achieves bidirectional, ultra-wide deformation through a synergistic light–moisture feedback mechanism. Inspired by the brick–mortar structure of nacre, a tannic acid (TA)/polyvinyl alcohol (PVA)/carbon nanofiber (CNF)/MXene composite film is fabricated and combined with a PTFE layer to construct a TPCM actuator with tunable mechanical strength (tensile strength up to 132.05 MPa, modulus 121.31 MPa). Under alternating light and humidity stimulation, photothermal heating and moisture absorption cooperatively modulate hydrogen bonding and polymer chain mobility, generating a positive feedback loop that amplifies actuation. The actuator exhibits bidirectional bending angles up to 261° (light) and 273° (humidity)—significantly exceeding deformation limits of single-stimulus systems. Leveraging this mechanism, bionic crawling robots, claw-like grippers, and water-lily-inspired structures are realized, and a soft optical shutters model is demonstrated. This work introduces a new paradigm for synergistically coupled multi-stimuli actuators, offering a general strategy for designing adaptive, high-performance MXene-based soft robotic systems.