Highly Sensitive and Stable Flexible Sensors Based on Antifreezing and Self-Healing Double-Network Composite Hydrogels for Human Motion Monitoring

Hydrogels exhibit ideal flexibility and biocompatibility, which have attracted the attention of many researchers in the field of flexible electronics. However, the challenge exists to endow hydrogel flexible sensors with higher strength, stretchability, excellent self-healing efficiency, and wide application temperature range. Herein, a stretchable, conductive, antifreeze, and self-healing hydrogel was prepared by implanting polyaniline (PANI)-coated cellulose nanocrystals (CNCs) and betaine into a gellan gum (GG)/poly(acrylic acid) (PAA) hybrid double network. Surprisingly, the fracture stress of the hydrogel could reach 1.51 MPa and the self-healing efficiency improved from 74.5 to 90.1%, which was attributed to the incorporation of CNCs-PANI. Meanwhile, the self-healing efficiency of the hydrogel could reach 72.8% within 7 h at −30 °C due to the introduction of the antifreeze agent betaine. The assembled hydrogel strain sensor possessed high sensitivity (GF = 4.6) within a large strain range and output a stable signal even at low temperatures. Overall, the developed flexible sensors are able to accurately capture various human motion signals over a broad temperature range.