Ultra-stretchable, self-healing, bonding, and skin-inspired conductive triple network hydrogel for wearable strain sensors and friction nanogenerators

Hydrogel-based flexible sensors hold significant potential for applications in skin-like electronics, human motion detection, and human-machine interfaces. The development of strain-sensitive hydrogel with high stretchability, self-healing, and high conductivity is highly sought after. A hydrogel sensor with a strain-sensitive semi-interpenetrating network consisting of polyacrylamide (PAM), poly(vinyl alcohol) (PVA), and sodium alginate (SA). With environmentally benign KCl as a conductive filler, SA/PVA/PAM/KCl hydrogel has a high toughness (4.8 MJ m⁻³), high stretchability (1250 %), high tensile strength (510 kPa), excellent recoverability, and excellent self-adhesiveness toward various substrates. The hydrogel sensors present high sensitivity with good linearity in the majority of the detection range with a gauge factor (GF) over 6.78, a response time of 268 ms, and excellent durability. The ionic conductive hydrogel has shown excellent energy harvesting capability as a triboelectric nanogenerators (TENG). Multifunctional organic hydrogels provide a protocol for the design and preparation of multifunctional hydrogel for wearable electronics.