Notch-insensitive, underwater adhesive, and self-healing ionic skins

Ionic skins (I-skins) mimic the sensing function of natural skin based on ionic conduction have essential applications in wearable sensors for human motion detections. However, the fragile, low electrical sensitivity, lack of adhesive and self-healing performances still limits their practical applications and service life. Herein, we reported an ionic skin which was fabricated by the ionic liquid, acrylic acid and Fe3+ through the one-pot method. The polyacrylic acid network is cross-linked by intermolecular hydrogen bonds and the complexation of Fe3+, where the ionic liquid can bind through reversible electrostatic interactions. Such design endows the resultant hydrogel with superior tensile properties (tensile strength 341 kPa, strain at break 2042%), good notch insensitivity, air/underwater dual adhesive property for the surface of various solid materials (including glass, iron, copper and aluminum) and excellent healability (self-healing efficiency as high as 80.5% at room temperature). In addition, the I-skin exhibits ultra-high electrical sensitivity (GF = 13.12) and an extensive strain monitoring range (5%–300%). Not only can it be used as expression and human motion detector, but also can realize “information programming”. The rich application scenarios and functions prove its potential to be used as wearable sensors.