Ultra-adhesive Poly(acrylic acid)-Based Hydrogel as a Flexible Sensor for Capturing Human-Motion Signal

Conductive hydrogels are widely applied in wearable sensors, soft robotics, and human-interactive devices owing to their unique physicochemical properties. Herein, we prepared an ultra-adhesive poly(acrylic acid)/Fe b /Li 2 SO 4 c hydrogel. The maximum peeling forces of the hydrogel with respect to an aluminum substrate and a titanium surface were 1380 and 1619 N·m –1, respectively. The elongation at break of the hydrogel was 2450%, and the breaking stress was 98 kPa. Owing to the synergistic effect of the −COOH–Fe 3+ complex and H bonds, the prepared hydrogels exhibited self-healing properties. Because of the presence of lithium sulfate, the hydrogel exhibited electrical conductivity (up to 0.0195 S·cm –1 ). The hydrogel could be used as a strain sensor with a gauge factor of 21.12. The high sensitivity of the hydrogel enabled it to quickly respond to changes in the speed and angle of human joint movements. Therefore, the hydrogel sensor could capture signals from low-amplitude movements such as speaking, smiling, and frowning. The simple preparation strategy for an adhesive, self-healing, frost-resistant, and conductive hydrogel reported herein can broaden the range of applications of wearable electronic devices.