Temperature-tolerant flexible supercapacitor integrated with a strain sensor using an organohydrogel for wearable electronics

Due to the increased demand for wearable devices, there has been extensive research on flexible energy storage devices (e.g., batteries and supercapacitors) and bio-signal monitoring sensors. For the practical application of wearable devices, stable operation regardless of the environmental temperature is required. In this study, we report a temperature-tolerant flexible supercapacitor based on a synthesized novel organohydrogel electrolyte designed to power an integrated strain sensor for the monitoring of bio-signals. The fabricated supercapacitor exhibits a remarkable gravimetric capacitance of 123.4F g⁻¹, 147.0F g⁻¹, and 156.2F g⁻¹ at temperatures of − 20 °C, 25 °C, and 80 °C, respectively. After three repetitive cycles shifting from − 20 °C to 80 °C, the initial capacitance is almost fully recovered. In addition, after 1000 cycles of bending deformation, the capacitance remains almost the same, thus verifying the flexibility of the device. A strain sensor fabricated using the same organohydrogel exhibits a change in resistance with stretching deformation, with a gauge factor of 1.77, 1.61, and 1.50 at 25 °C, −20 °C, and 80 °C. By vertically integrating the supercapacitor and strain sensor, various bio-signals, including finger bending and swallowing are successfully detected using the stored energy of the supercapacitor. As a whole, the results highlight the potential of our proposed temperature-tolerant flexible device fabricated based on a single organohydrogel for use in wearable applications that are stable over a wide range of environmental temperatures.