Stretchable and environment-resistant doubly crosslinked hydrogel for all-in-one supercapacitor and strain sensors

Despite their importance as components for flexible electronics, most stretchable hydrogels suffer from incomplete recovery after deformation, are prone to failure upon long-term repeated stretching, and cannot be exploited at subzero temperatures because of the freezing of their constituent water. Consequently, strategies for circumventing these drawbacks are highly sought after. This study describes the synthesis of a doubly (chemically and physically) crosslinked hydrogel from gelatin and methacrylic acid and demonstrates the suitability of this material for the fabrication of high-performance stretchable and environment-resistant supercapacitors and strain sensors. The performance of this supercapacitor (areal capacitance = 1210.2 mF cm −2  at a current density of 1 mA cm −2 , maximum energy density = 158.8 μW h cm −2 , maximum power density = 659.5 μW cm −2 ) was superior to that of most of integrated supercapacitors reported to date and was hardly affected by stretchable, low temperatures, bending, ice-cold water and strong acid/alkali solutions or long-term storage. Additionally, a strain sensor based on the above hydrogel was capable of accurately capturing human body motions when affixed to skin and recognising mouse movement (even in humid environments) after implantation into mouse legs. Our work may pave the way to high-performance stretchable and environment-resistant wearable electronics.