Highly Stretchable, Self-Healable, Freezing-Tolerant, and Transparent Polyacrylic Acid/Nanochitin Composite Hydrogel for Self-Powered Multifunctional Sensors

To fulfill the current challenges in the hydrogel applications in wearable sensors including low sensitivity, lack of self-healing ability, and non-transparency, we synthesized a polyacrylic acid/nanochitin composite hydrogel with dual cross-linking networks for highly stretchable, transparent, self-healing, and anti-freezing sensors via an eco-friendly method. Dynamic metal-coordination bonds between Al3+ and carboxyl groups and the hydrogen bonds contributed to the excellent self-healing efficiency of the hydrogel (97%). The dual cross-linking networks provide the composite hydrogel with 400 kPa tensile strength. The hydrogel-based sensors could detect multiple external stimuli, demonstrating a high gauge factor of 2.36 with the strain range of 0-500% and an ultrabroad temperature detection range (-35 to 50 °C). Significantly, the composite hydrogel demonstrates an ultrasensitive thermal response with a sensitivity of 252 %/°C during the cooling process. Moreover, the composite hydrogel was also assembled into a triboelectric nanogenerator to act as a self-powered pressure sensor. Therefore, the developed hydrogel sensors fabricated via a facile and green preparation approach hold great potential for sustainable wearable sensors in electronic skins and personal healthcare.