Toughened, self-healing and self-adhesive conductive gels with extraordinary temperature adaptability for dual-responsive sensors

Abstract

Conductive hydrogels are considered as highly promising candidates for fabricating flexible and wearable electronic devices. However, traditional hydrogels inevitably lose their inherent characteristics under extreme climatic conditions, which seriously hinders the practical application of hydrogel-based electronics. Herein, a toughened, self-healing, self-adhesive and transparent conductive gel (PAA-Zr⁴⁺/Gly/IL) with extraordinary temperature adaptability is prepared via a one-step photopolymerization of the acrylic acid (AA) monomer in Gly (glycerol)–IL ([Bmim]Cl) hybrid solvent containing Zr⁴⁺ ions. The carboxyl–Zr⁴⁺ coordination bonds and multiple hydrogen bond interactions within the gel networks contribute to the excellent mechanical properties (0.42 MPa at 1436% strain) and self-healing capability. Meanwhile, the synergistic effects of Gly and IL endow the as-prepared gel with significant temperature tolerance, which can maintain remarkable flexibility and mechanical strength even after being stored at −50, 20 and 50 °C for 30, 30 and 10 days without extra sealed packaging. Impressively, the PAA-Zr⁴⁺/Gly/IL gel-based sensors exhibit favorable sensitivity and repeatable response capability upon both mechanical and thermal stimulation. As a strain sensor, it demonstrates a wide sensing range (5–700%), prominent signal stability (1100 cycles at 300% strain) and precise human motion detection along two opposite directions. As a thermal response sensor, it can accurately and reliably sense temperature changes in a wide range from −50 to 50 °C. Noticeably, owing to the significant self-healing properties and temperature tolerance, the pristine and healed PAA-Zr⁴⁺/Gly/IL gels after long-term storage at various temperatures (−50, 20 and 50 °C) are also capable of demonstrating a recognizable and reliable signal response when detecting tensile strains and prosthetic finger bending movements in normal and harsh environments. This work provides a powerful strategy to design versatile conductive elastomers with broad and long-term temperature tolerance for future flexible and wearable electronics.