Programming electronic skin with diverse skin-like properties

Abstract

Simulating the comprehensive functions of native skin—and not simply the perception of external physical stimuli—by electronic skin (e-skin) has gathered increasing attention in the development of wearable devices and human-interactive technology. Here, we report an anti-bacterial, color-variable, ultraviolet (UV)-sensitive, shape-adaptive, and immunoregulatory e-skin based on a single- and dual-network switchable hydrogel composed of a covalent network of polyacrylamide (PAAm) and a coordinated network of xanthan gum (Xg)/iron ions [Fe(III)]. In the presence of sodium lactate and UV exposure, Fe(III) could be reduced to Fe(II), which de-coordinated the Xg/Fe(III) network. During this reduction process, the e-skin realized three functions of real skin: (i) UV triggered a color change with detectable resistance alterations; (ii) reactive oxygen species (ROS) were dramatically produced to defend against pathogens; and (iii) the piezoresistant hydrogel became highly stretchable to perceive all-scale human motions. Moreover, the shear-thinning properties of Xg in the precursor solution allowed the e-skin to be printable, and the anti-inflammatory functions of de-coordinated Xg were beneficial for wound healing. In summary, this newly-developed e-skin can achieve the perception of UV and human motions. It has promising applications for irregularly-shaped body surfaces and infected wounds.