Ultrastretchable\nand Stable Strain Sensors Based on\nAntifreezing and Self-Healing Ionic Organohydrogels for Human Motion\nMonitoring

Abstract

Ionic hydrogels, a class of intrinsically\nstretchable and conductive\nmaterials, are widely used in soft electronics. However, the easy\nfreezing and drying of water-based hydrogels significantly limit their\nlong-term stability. Here, a facile solvent-replacement strategy is\ndeveloped to fabricate ethylene glycol (Eg)/glycerol (Gl)-water binary\nantifreezing and antidrying organohydrogels for ultrastretchable and\nsensitive strain sensing within a wide temperature range. Because\nof the ready formation of strong hydrogen bonds between Eg/Gl and\nwater molecules, the organohydrogels gain exceptional freezing and\ndrying tolerance with retained deformability, conductivity, and self-healing\nability even stay at extreme temperature for a long time. Thus, the\nfabricated strain sensor displays a gauge factor of 6, which is much\nhigher than previously reported values for hydrogel-based strain sensors.\nFurthermore, the strain sensor exhibits a relatively wide strain range\n(0.5–950%) even at −18 °C. Various human motions\nwith different strain levels are monitored by the strain sensor with\ngood stability and repeatability from −18 to 25 °C. The\norganohydrogels maintained the strain sensing capability when exposed\nto ambient air for nine months. This work provides new insight into\nthe fabrication of stable, ultrastretchable, and ultrasensitive strain\nsensors using chemically modified organohydrogel for emerging wearable\nelectronics.