A Cellulose Salt Gel with Mechanical Transformation and Thermal Control

Abstract Gels as compelling soft material shows its promising versatility in actuators, soft electronics, and biomedical sensors. However, most gel materials are too rigid to cope with long‐term changing scenarios and specific needs. Inspired by the switchable behavior of bio‐behavior of muscle, the study reports a thermodynamically controllable and stiffness‐transformative cellulose‐salt gel by simple thermal mixing of hydrous salt, cellulose nanofiber, and polyacrylamide. The achieved cellulosic gel with dynamic microstructure presents an amazing stiffness switchability between crystalline state and melted states of 32.38 to 0.02 MPa, as well as the regulable light transmittance between 41.59% and 93.43%. In addition, this cellulose‐salt gel has excellent thermal controllable behavior. That is, by controlling the crystallization process, the cellulose‐salt gel displays the start‐stop releasing‐energy behaviors on demand. Enabled by these outstanding properties, the study further demonstrates the promising application of cellulose‐salt gel in controllable soft‐rigid coupling thermoelectric device, showing the broader implications for wearable electronics aiming at on‐demand work.