Self-Adaptable Deep Eutectogels with High Stretchability, Low Hysteresis, and Long-Term Stability for Wearable Strain Sensors

Abstract

Hydrogels are widely used in wearable flexible sensors, but suffer from dehydration, freezing, and bacterial growth under harsh environments. Here, we present a low-hysteresis eutectogel by incorporating quaternary ammonium chitosan (QCS) into an electrostatically driven supramolecular network prepared from acrylic acid (AA) and betaine deep eutectic solvent. The addition of QCS not only forms hydrogen bonds with poly(acrylic acid) (PAA) and betaine to create a supramolecular network, but also acts as a “physical cross-linker” by “anchoring” the polymer molecular chains together. The eutectogel exhibits excellent stretchability (∼1800%), low hysteresis (<10%), strain sensitivity (GF = 7.02 at 700–900% strain), fast response (46 ms), long-term stability (>14 days) and antifreezing abilities (−30 °C). In addition, the eutectogel also demonstrates good biocompatibility, bacteriostatic ability and 3D printability. A PDES/QCS-based sensor integrating deformation and temperature sensing offers exceptional environmental adaptability. Furthermore, the eutectogel can be assembled with zinc and copper foils as a self-powered device, where the open circuit voltage of each individual device can reach around 0.8 V. Hence, this study presents an efficient material design strategy for flexible sensing materials that integrate various functions and demand high environmental stability.