Nanocomposite Multi-Cross-Linked Hydrogels with High Strength, High Stretchability and High Conductivity for Multifunctional Wearable Sensors

Conductive hydrogels have gained significant attention in advanced fields like wearable devices and soft robotics. However, the concurrent fabrication of wearable sensors based on hydrogels with both optimal mechanical properties and high conductivity remains a significant challenge due to the inherent brittleness of conventional hydrogels and the absence of conductive pathways within them. Addressing this challenge, this study successfully developed a nanocomposite multicross-linked hydrogel with high strength, high stretchability and high conductivity. The structure comprises a chemically cross-linked polyacrylamide (PAM) network and entangled gelatin chains induced by the Hofmeister effect. Multiple hydrogen bonds between gelatin, PAM, water molecules, carboxylated multiwalled carbon nanotubes (c-MWCNTs), and chitosan (CS) enhance the hydrogel's crosslink density and stability. The hydrogel exhibits remarkable mechanical performance, with a tensile strength of 0.83 MPa, stretchability over 1558%, and toughness of 5.04 MJ/m3, alongside excellent fatigue resistance and self-healing capabilities. The hydrogel also shows high conductivity (5.09 S/m), sensitivity (GF = 1.91), and durability (over 100 cycles), enabled by conductive pathways formed by c-MWCNTs and inorganic salt electrolytes. The prepared strain sensors show a wide range of applicability and high reliability in the field of human motion monitoring, where both large movements of joint bending (including elbow, wrist and knee) and small movements such as smiling and swallowing can be accurately monitored. Moreover, it can transmit information by analyzing electrical signal changes, suggesting innovative potential for communication applications. Thus, this nanocomposite hydrogel holds great promise for health monitoring and remote communication.