Graphite-doped flexible conductive hydrogel temperature-strain sensor

Conductive hydrogels have wide use in multifunctional sensors. Nevertheless, the intrinsic features of conductive hydrogels, including the absence of sensation mechanisms with varied properties, impede their application in wearable devices. To this end, this paper fabricated a novel 3D network material, namely C/PVA/CaCl2/HK (CPCH) hydrogel, that comprises incorporation of graphite (C), calcium chloride (CaCl2), hydrolyzed keratin (HK), and the polyvinyl alcohol-based (PVA-based) hydrogel. The CPCH hydrogel and the CPCH secondary hydrogel both exhibit impressive mechanical properties. The former features a maximum stress of 2.98 MPa and a maximum strain of 588 %, while the corresponding values of the latter are 1.590 MPa and 573 %, respectively. Additionally, the result showed a maximum reflected light barrier of the CPCH hydrogel at a wavelength of 248 nm. The study found that the CPCH hydrogel holds the fingers attached to the upper surface during heating for up to 10 s, demonstrating superior heat insulation performance. The gel fraction analysis revealed that the gel makes up 57.1 % of our prepared CPCH hydrogel with a porosity of 62.5 %. Besides, we conducted a conductivity test on the proposed hydrogel, obtaining a measured conductivity value of 0.04 mS/cm. Furthermore, its practicality and feasibility have been confirmed via experiments. The results show that the CPCH conductive hydrogel can potentially be a temperature-strain sensor for wearable devices. [Display omitted] •Discovering a new type of material that can be reused.•Doping graphite can significantly enhance the mechanical properties of the material.•Doping graphite enhances the hydrogel's conductivity and flexibility, thereby improving the sensor's performance.•The temperature-strain sensor made of flexible conductive hydrogel exhibits good reliability and stability.