Adhesive Ionohydrogels Based on Ionic Liquid/Water Binary Solvents with Freezing Tolerance for Flexible Ionotronic Devices

Abstract

Ionic hydrogels hold substantial promise as soft materials for achieving versatile wearable ionotronics due to the integrated merits of appropriate mechanical properties, excellent conductivity, and good conformability. However, overcoming freezing at subzero temperatures and hindering the evaporation of water are still huge challenges for ionic hydrogels. Herein, a dual-cross-linked ionohydrogel was designed using Al3+ to cross-link with the polymer network through dynamic metal coordination bonds in the water and ionic liquid (IL) binary solvent system, allowing for excellent mechanical properties (∼1 MPa, ∼600%), transparency (>90%), high ionic conductivity (∼12.40 mS cm–1), and robust adhesion, along with the advantages of superior antifreezing and long-term antidehydration properties. These exceptional characteristics inspired us to fabricate dual-responsive sensors, which could simultaneously detect human motion signals and a wide range change of temperatures (from −30 to 40 °C) with an impressive temperature coefficient of resistance (TCR) value (from −0.035 to −0.44 °C–1). More promisingly, benefiting from the superior interfacial adhesion between the poly(dimethylsiloxane) (PDMS) and the ionohydrogels, a triboelectric nanogenerator was assembled with a single-electrode mode that was capable of providing sustainable energy for wearable ionotronic devices even at subzero temperatures. This work opens up an effective strategy to design a multifunctional ionohydrogel, enabling various applications integrated into the single device.