Skin-Adherent, Cellulose-Based Photonic Patch for Visual Strain Mapping

Electronic skin (E-skin), mimicking the multisensory response of human skin, is increasingly utilized in diverse applications such as health monitoring and sensory skins. Here, inspired by the diverse adhesion and responsive structural color phenomena in biological interfaces, we present a cellulose-based, skin-adherent photonic E-skin (CSPE) for dual-mode visual and electrical strain sensing. The CSPE combines a cellulose nanocrystal (CNC)-based conductive, tough photonic hydrogel with a bridging chitosan interlayer that binds the photonic gel and skin together. Endowed with the ionically crosslinked double-network hydrogel as the mechanochromic dissipative matrix and pH-responsive chitosan for topological interpenetration, the CSPE exhibits anisotropic adhesion, ensuring good skin adhesion and preventing unwanted attachments on the opposite surface. Additionally, the photonic hydrogel with vivid structural colors provides quantitative feedback of mechanical stimulation via color mapping and electromechanical changes, enabling precise tracking of human movements. This proposed skin-adherent photonic skin can widen the practical value of bionic electronic skins.