C-lignin-enabled multifunctional hydrogels for flexible wearable sensors

Manufacturing ionic conductive hydrogels (ICHs) integrating excellent mechanical properties, high ionic conductivity, antifreezing performance, and adhesion in an environmentally friendly manner is crucial for engineering and smart electronics applications. However, it is challenging to reconcile the paradox of the abovementioned functionalities. In this study, we first prepared an anionic C-lignin sulfonate, which can couple with cationic poly(imidazolium-acrylamide), thus inducing electrostatic interactions between their polymeric skeletons and forming a macroscopically homogeneous covalent network with in situ phase separation. The C-lignin-enabled ICHs exhibit exceptional stretchability (∼600 % strain), high toughness (∼323 kJ m^-3), a modulus comparable to human skins (∼40.30 kPa), excellent conductivity (∼7.4 mS cm^-1), and strong adhesion. Furthermore, the ICHs demonstrated excellent antifreezing performance, maintaining nearly unchanged mechanical properties and adhesion, along with acceptable ionic conductivity at -30 °C. The ICHs can be assembled as strain sensors with a wide working strain range of 3 % to 300 % and high sensitivity (GF = 1.52), enabling precise monitoring of various human movements. This study offers a promising strategy for sustainable biopolymer C-lignin- enabled ICH materials, highlighting the interaction and balance between opposing elements.