Robust conductive skin hydrogel e-skin constructed by top–down strategy for motion-monitoring

The construction of biomass-based conductive hydrogel e-skins with high mechanical properties is the research hotspot and difficulty in the field of biomass materials. Traditional collagen-based conductive hydrogels, constructed by the typical “bottom–up” strategy, normally have the incompatible problem between high mechanical property and high collagen content, and the extraction of collagen is often necessary. To solve these problems, inspired by the high mechanical properties and high collagen content of animal skins, this work proposed a “top–down” construction strategy, in which the extraction of collagen was unnecessary and the skin collagen skeleton (SCS) with the 3D network structure woven by natural collagen fibers in goatskin was preserved and used as the basic framework of hydrogel. Following a four-step route, namely, pretreatment → soaking in AgNPs (silver nanoparticles) solution → soaking in the mixed solution containing HEA (2-hydroxyethyl methacrylate) and AlCl₃ → polymerization, this work successfully achieved the fabrication of a new skin-based conductive hydrogel e-skin with high mechanical properties (tensile strength of 2.97 MPa, toughness of 6.23 MJ·m⁻³ and breaking elongation of 428%) by using goatskin as raw material. The developed skin hydrogel (called PH@Ag) possessed a unique structure with the collagen fibers encapsulated by PHEA, and exhibited satisfactory adhesion, considerable antibacterial property, cytocompatibility, conductivity (3.06 S·m⁻¹) and sensing sensitivity (the maximum gauge factor of 5.51). The PH@Ag e-skin could serve as strain sensors to accurately monitor and recognize all kinds of human motions such as swallowing, frowning, walking, and so on, and thus is anticipated to have considerable application prospect in many fields including flexible wearable electronic devices, health and motion monitoring.

Graphical abstract