Nanolignin filled conductive hydrogel with improved mechanical, anti-freezing, UV-shielding and transparent properties for strain sensing application

Herein, we innovatively synthesized an ionic conductive PVA/LNP hydrogel with integrated excellent mechanical, anti-freezing, moisturizing, transparent and UV-shielding performances via incorporating nanolignin (also called lignin nanoparticle, LNP) and aluminum chloride (AlCl3) into polyvinyl alcohol (PVA) matrix containing ethylene glycol/water (EG/H2O) binary solvent. The rigid porous network structure was well constructed by the hydrogen bond interactions among the evenly distributed LNP and PVA chains, thus providing abundant ion transport channels, which attributed to the outstanding ionic conductivity (up to 1.35 x 10(-2) S/m, at -24 degrees C) with improved mechanical strength and flexibility. The tensile strength and elongation at break of PVA/LNP hydrogel were greatly increased from 574.6 kPa and 363.7% to 1241.4 kPa and 589% at the addition of 0.35% LNP, respectively. In addition, the UV-resistance ability was 95% at 365 nm, while the transparency was 74% at 550 nm. The binary solvent of EG and H2O ensured long-term moisturizing capability (10 days) of the hydrogel at 35 degrees C and 60 RH%, as well as possessing superior anti-freezing performance over the temperature range of -62.6 to 24 degrees C. As a result, the fabricated PVA/LNP hydrogel was successfully used as strain sensor for detecting diverse human motions and electrophysiological signals.

Automated summary

In this study, an ionic conductive PVA/LNP hydrogel with excellent mechanical, anti-freezing, moisturizing, transparent, and UV-shielding performances was innovatively synthesized. The hydrogel was constructed with a rigid porous network structure through the interactions between evenly distributed LNP and PVA chains. It exhibited outstanding ionic conductivity, improved mechanical strength, and flexibility. The hydrogel also showed increased tensile strength, elongation at break, UV-resistance ability, and transparency. Moreover, the hydrogel had long-term moisturizing capability and superior anti-freezing performance. It was successfully used as a strain sensor for detecting human motions and electrophysiological signals.