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 state). 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 ploy (vinyl alcohol) (PVA) chains and poly [N, N dimethyl (methylacryylethyl) ammonium propane sulfonate] (PDMAPS)/polyacrylamide (PAM) block copolymer chains provide abundant hydrogen bonds and cation-anion dipole interactions; meantime, dimethyl sulfoxide and CaCl2 are added to further improve the mechanical properties, and to facilitate the conductivity and anti-freezing property. By systematically optimizing the multi-intercations among these components, the organohydrogel reaches high tensile strength (2.7 MPa), high stretchability (630%), considerable ionic conductivity (2.4 mS cm-1 at RT). More importantly, it achieves remarkable stability in a wide temperature range of -40~80℃. Then, the organohydrogel sensors in resistive- and triboelectric nanogenerator (TENG)-mode are demonstrated for strain/temperature sensing, and non-contact distance/materials sensing, respectively, suggesting their great potentials in flexible electronics in the future.