Mussel-Mimicking Multifunctional Carboxymethyl Cellulose-Based Conductive Hydrogel as a Wearable Strain Sensor for Underwater Applications

Conductive hydrogels have been increasingly designed as wearable strain sensors due to their significant potential in human motion monitoring and health detection applications. However, the integration of multiple desirable characteristics within a single hydrogel system remains challenging. Furthermore, environmental factors such as humidity and low temperatures often compromise hydrogel sensor functionality, substantially limiting their practical applications and value. In this study, we developed a mussel-inspired multifunctional CACa conductive hydrogel through in situ polymerization by incorporating polyacrylamide (PAM), tannic acid (TA), carboxymethyl cellulose (CMC), and aminated carbon nanotubes (NH2–CNTs) into a unified gel network. By optimizing the CMC mass fraction and subsequent cross-linking via calcium chloride (CaCl2) solution immersion, the resulting hydrogel demonstrates exceptional stretchability, self-adhesion, moisturizing/antifreezing capabilities, conductivity, and underwater adhesion. As a self-adhesive wearable strain sensor, CACa hydrogel can directly adhere to human skin without external assistance. It exhibits high sensitivity and rapid response to various physiological signals, including finger flexion, wrist rotation, elbow movement, and throat vibration during speech. Remarkably, this flexible electronic material maintains functionality even under subzero temperatures and aqueous environments. The hydrogel’s underwater adhesion enables effective motion signal detection and information transmission in submerged conditions. This work provides insights for developing advanced wearable sensors and underwater monitoring devices, significantly expanding the potential applications of multifunctional conductive hydrogels.