Self-Healing Ionic Skins with Moisture Self-Regulation Characteristics for Ultra-Long Ambient Stability

Vulnerability to mechanical damages and dehydrations limits the operations of conductive hydrogels in ambient conditions. Inspired by the self-healing and water regulation behavior of jellyfish, we designed hydrogel-based self-healable ionic skins that can self-regulate internal moisture level by exploiting the mutually cohesive interactions among water, ions, and zwitterionic polymer networks. The material can sustain in the ambient for an ultra-long period of over 16 months and exhibit high stretchability (>1650% strain) and conductivity (as high as 23.5 mS/cm). Furthermore, after incidental exposures to harsh environments, including heating at 200 °C, freezing and vacuum drying conditions, the hydrogel can self-replenish water content from the ambient moisture and regain most of its conductivity and stretchability. Meanwhile, reversible ionic and hydrogen bonds allow the material to heal from fully cut-through damages repeatedly recouping conductivity (>90%) at room temperature within one minute. Utilizing the ionic skins as building blocks, flexible transparent piezoelecret sensors have been constructed to monitor physiological signals. Additionally, a facile transfer-printing process has been introduced to fabricate a breathing sensing system with self-healable supercapacitor and humidity sensor printed directly on ionic skins. These demonstrations illustrate broad-ranging possibilities of the ionic skin in areas including energy storage devices, wearable sensors, and human-machine interfaces.