Stable, Strain-Sensitive Conductive Hydrogel with Antifreezing Capability, Remoldability, and Reusability.

Conductive hydrogels have important potential in biosensors, bioactuators, and health recording electrodes, but they are often troubled by sensitivity, operating temperature range, and whether they can be recycled or not. In this paper, conductive hydrogels poly(vinyl alcohol)/glycerol/polyaniline (PGA) were prepared by organic combination of low-cost poly(vinyl alcohol) (PVA), polyaniline (PANi), and glycerin. First, the effects of PVA, glycerol, and aniline/phytic acid solution concentration on the mechanical properties, electrical properties, and frost resistance of the PGA gel were discussed. Second, the interaction energies of PVA, PANi, phytic acid, glycerol, and water molecules were analyzed by Materials Studio. Then, a simple biosensor fabricated using the PGA gel realized the detection of the conventional motion signal of the human body. The conductive gel has high sensitivity (GF = 2.14), fast response time (230 ms), and can be circulated several times (∼540 cycles). Furthermore, the PGA conductive gel can maintain good electrical conductivity (0.32 S/m) and mechanical properties even at -20 °C. Also, the gel can be recovered by injection heating, cooling, and cyclic freeze-thaw three-step method. It is believed that the PGA conductive gel would be used as a novel multifunctional material at subzero temperatures in various fields, such as flexible electrode, sensors, and wearable devices.