ZIF-8-enhanced multifunctional, high-performance nanocomposite hydrogel-based wearable strain sensor for healthcare applications

The rapid growth of strain sensors in cutting-edge applications, including wearable human-machine interfaces, electronic skins, soft robotics, and advanced healthcare, has greatly heightened the demand for high-performance hydrogels. In this report, we demonstrate a multifunctional, highly stretchable, and robust conductive hydrogel composed of polyacrylamide (AM), 2-hydroxyethyl acrylate (HEA), and lithium chloride (LiCl) reinforced by zeolite imidazolate frameworks-8 (ZIF-8) through a one-pot free radical polymerization method. The synergy of electrostatic interactions between the AM-HEA polymer chain and nanoporous ZIF-8 enhances the mechanical properties, while the abundant hydrogen bonds originating from the polarized surface of ZIF-8 also introduce multifunctionality to the nanocomposite hydrogel. Tuning the composition of ZIF-8 within the hydrogel matrix results in the attainment of outstanding properties such as excellent stretchability of 808%, high toughness of 453.5 kJm-3, and minimal hysteresis as low as 2.6%. Notably, the nanocomposite hydrogel displays strong adhesion, self-healing properties, and resilience in freezing temperatures down to - 20 degrees C. Furthermore, the as-developed strain sensor exhibits relatively high sensitivity with a gauge factor of 2.98 across a wide dynamic range, along with fast response and recovery times of 280 ms and 330 ms, respectively. The multifunctionality and electromechanical properties of ZIF-8 enhanced high-performance hydrogel hold promise for its application as a wearable, flexible, and stretchable strain sensor for detecting human physiological activities and providing vital biomechanical information for health assessment.