Biocompatible, self-wrinkled, antifreezing and stretchable hydrogel-based wearable sensor with PEDOT:sulfonated lignin as conductive materials

Gel-based strain sensors have great potential in the fields of motion detection and real-time healthcare. Nevertheless, the relatively low strain sensitivity and inferior anti-freezing property limit the utilization of these sensors. In this work, a novel multifunctional organohydrogel sensor was developed based on a poly (acrylic acid) (PAA) skeleton with poly (3,4-ethylenedioxythiophene): sulfonated lignin (PEDOT:SL) as the conductive material and a water/glycerol binary solvent as the dispersion medium. The conductive, self-wrinkled, soft and elastic properties endue the organohydrogel sensor with a superior gauge factor (GF) of up to 7 (strain: 100%), while the freezing tolerance of the water/glycerol solvent endows the organohydrogel with an excellent anti-freezing property. The organohydrogel sensor senses not only the movement of limbs, but also a weak pulse and throat vibrations. Moreover, physiological signals such as those used for electrocardiography (ECG) and electromyography (EMG) can be readily detected. In addition, the cell culture test shows that the organohydrogel is nontoxic, and the animal experiments demonstrate that the organohydrogel can protect skin from frostbite. Overall, this work presents a new concept to use lignin for conductive PEDOT polymerization and integrates the fabrication of conductive organohydrogel materials for precise strain sensing.