Hydrogen-bonded network enables semi-interpenetrating ionic conductive hydrogels with high stretchability and excellent fatigue resistance for capacitive/resistive bimodal sensors

The construction of ionic conductive hydrogels with complex deformation tolerance and excellent fatigue resistance is highly demanded yet challenging. Herein, a semi-interpenetrating ionic conductive hydrogel (SICH) is fabricated by a hydrogel-network constrained polymerization of 1-butyl-3-vinylimidazole tetrafluoroborate and acrylic acid in polyethylene oxide aqueous solution. Ascribing to the formation of a dense intermolecular hydrogen-bonded network, the SICH is capable of being stretched up to ~300%, compressed to ~85%, and recovered immediately when the external force is fully released. The SICH can readily work as a high deformation-tolerant ionic conductor for capacitive/resistive bimodal ionic sensors. The ionic sensor not only showed a wide response range to dynamic pressures (0–8 kPa) and excellent cycling stability (500 cycles) in a capacitive mode, but also demonstrated high sensitivity (gauge factor of ~1.1), excellent linear response (0–300% strain) and fast response time (80 ms) in a resistive mode. As a demonstration, a wearable bimodal SICH ionic sensor was assembled, showing high sensitivity, linearity, wide response range and great durability in detecting complex human motions including speaking and various joint bending.