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

• An organohydrogel based supercapacitor with temperature tolerance was fabricated. • The supercapacitor was stable with repeated temperature changes between -20 and 80 ℃. • The capacitance was stable under bending deformations regardless of temperature. • The strain sensor with the same oragnohydrogel exhibited the temperature tolerance. • By integrating the supercapacitor and strain sensor, bio-signals were detected. 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 123.4 F g -1 , 147.0 F g -1 , and 156.2 F g -1 at temperatures of −20 ℃, 25 ℃, and 80 ℃, respectively. After three repetitive cycles shifting from −20 ℃ to 80 ℃, 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 ℃, −20 ℃, and 80 ℃. 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.