Multi-crosslinked strong, tough and anti-freezing organohydrogels for flexible sensors

Hydrogels are promising sensing materials for various smart and biocompatible applications; nevertheless, it is still challenging to enhance their mechanical property and stability in wide temperature windows and under extreme conditions (such as dry and swelling states). Herein, we report a strong, tough, anti-freezing and anti-dehydration organohydrogel achieved by designing a dual-network structure with multi-crosslinking interactions. The interpenetrated poly (vinyl alcohol) (PVA) chains and poly[<i>N</i>,<i>N</i>-dimethyl(methylacrylethyl)ammonium propane sulfonate] (PDMAPS)/polyacrylamide (PAM) block copolymer chains provided abundant hydrogen bonds and cation-anion dipole interactions; besides, dimethyl sulfoxide and CaCl₂ were added to further improve the mechanical properties as well as facilitate the conductivity and anti-freezing property of the organohydrogel. By systematically optimizing the multi-interactions among these components, the organohydrogel achieved high tensile strength (2.7 MPa), high stretchability (630%), and considerable ionic conductivity (2.4 mS cm^-1 at RT). More importantly, it achieved remarkable stability in a wide temperature range of -40 to 80 °C. Moreover, organohydrogel sensors in resistive and triboelectric nanogenerator (TENG) modes were demonstrated for strain/temperature sensing and non-contact distance/material sensing, respectively, suggesting their great potentials in flexible electronics in the future.