An ambient-stable and stretchable ionic skin with multimodal sensation
Skin serves as physical and hygroscopic barriers to protect the inner body, and also contains sensory receptors to perceive environmental and mechanical stimuli. To recapitulate these salient features, hydrogel-based artificial skins have been developed. However, existing designs are constrained by limited functionality, low stability, and requirement of external power. Herein, a novel artificial ionic skin (AIskin)-an analog of the diode based on controlled ion mobility-is demonstrated with high toughness, stretchability, ambient stability and transparency. The AIskin consists of a bilayer of oppositely-charged, double-network hydrogel, and converts mechanical stimuli and humidity into signals of resistance, capacitance, open-circuit voltage (OCV), and short-circuit current (SCC), among which the OCV- and SCC-based sensing signals are self-generated. Its multimodal sensation maintains in a wide range of relative humidity (13%~85%). It is demonstrated for wearable strain-humidity sensing, human-machine interaction and walking energy harvesting. This work will open new avenues toward next-generation, skin-inspired wearable electronics.