A transparent ionic conductive poly (vinyl alcohol)/poly (γ-glutamic acid)/LiCl hydrogel with long-lasting anti-freezing, water retention, self-adhesion, self-healing and self-regeneration for wearable sensors

Hydrogels have aroused increasing attention as flexible and wearable electronic devices due to their unique properties and multifunctionalities. Herein, a novel dual network ionic conductive poly (vinyl alcohol)/poly (γ-glutamic acid)/lithium chloride (LiCl) hydrogel with 25 wt% LiCl (PVA/γ-PGA/LiCl 0.25 ) exhibited high transparency (91.12 %), excellent anti-freezing (−80 °C), good water retention (maintain 88 % of the initial water content after 7 days at 25 °C, 44 % RH), high conductivity (11.29 ± 0.13 S/m), good flexibility (491.71 ± 17.47 %), self-healing (∼100 %, 4 h) and self-regeneration abilities were successfully developed. Meanwhile, the conformal adhesion between the PVA/γ-PGA/LiCl 0.25 hydrogel-based strain sensor and skin due to the formed hydrogen bonds, which was conductive to the generate accurate, stable, and recyclable electrical signals with excellent sensitivity (GF = 5.61). In view of these merits, the PVA/γ-PGA/LiCl 0.25 hydrogel-based sensors not only precisely captured human motions with high strain, but also succeeded in sensitively detecting slight movements of face and throat. Notably, the assembled triboelectric nanogenerators (TENGs) tactile sensors and capacitive pen by using PVA/γ-PGA/LiCl 0.25 hydrogels has provided the possibility for human-computer interaction. These applications indicated that the developed PVA/PGA/LiCl 0.25 hydrogel have great potential in the fields of wearable electronics for human motion detection, self-powered devices and human-computer interaction.