Ca2+-coordinated CMC enhanced PVA/PAM hydrogels for wearable strain sensors

Poly(vinyl alcohol) (PVA)/polyacrylamide (PAM) double-network hydrogels have attracted extensive attention due to their excellent comprehensive performance. However, it remains a challenge for traditional PVA/PAM double-network hydrogels to integrate excellent mechanical properties with low mechanical hysteresis. Herein, Ca 2+ -coordinated carboxymethyl cellulose (CMC) was introduced into PVA/PAM hydrogels to prepare Ca 2+ -coordinated CMC enhanced PVA/PAM hydrogels (Ca 2+ -CMC-PVA/PAM) with a “sacrificial network” formed by dynamic metal coordination bonds between calcium ions and carboxymethyl cellulose. Under the synergistic effect of multiple networks, metal coordination, and hydrogen bonding, the Ca 2+ -CMC-PVA/PAM hydrogel achieved excellent tensile strength (142.8 kPa), elongation at break (805.1%), and toughness (0.585 MJ/m 3 ). In addition, the Ca 2+ -CMC-PVA/PAM hydrogel also possesses high sensitivity (GF = 1.87), fast response (200 ms), and fatigue resistance. At the same time, encapsulating it on human joints enables real-time detection of human motion, and its application can be extended to the field of encrypted communication by using Morse code for real-time information transmission. This work proposes a new design strategy for multifunctional hydrogel sensors, enabling seamless integration and precise interaction between biological tissues and electronics.