Transparent Conductive Hydrogels with Water-Responsive Contractility, Repairability, and Biocompatibility for Visible Conformal Shape-Adaptive Tissue-Adherent Monitoring

The conformal integration of flexible electronic devices on curved surfaces of target objects remains challenging, particularly for soft tissues with arbitrary and changeable shapes. Herein, transparent conductive hydrogels are developed for visible conformal shape-adaptive tissue-adherent monitoring, in which the water-responsive contractility, repairability, and biocompatibility are simultaneously achieved. The hydrogel is designed with poly (ethylene glycol) (PEG)-α-cyclodextrin (α-CD)/polyethylene oxide (PEO) and polyvinyl alcohol (PVA) double-crosslinking network, in which water as a mild stimulus can disrupt the directional arrangement of crystalline and molecular chains in PEO to trigger efficient contraction, whereas the bonding between α-CD and PVA ensures sufficient in-water mechanical repeatability. Besides, a binary solvent of glycerol and water is developed to effectively repair the dehydrated hydrogel after long-term use with full recovery. Moreover, excellent biocompatibility is verified by in vitro cytotoxicity test and in vivo subcutaneous implantation experiment. The conductive hydrogel could be adhesively wrapped on soft epidermis skins and internal organs of the heart and tendons in a conformal shape-adaptive way for physiological and motion signal monitoring with visual observation of the covered tissue health status. This multifunctional hydrogel provides an innovative paradigm for developing next-generation intelligent bioelectronic devices towards broad applications in health management, clinical diagnosis and tissue engineering.