Skin-Adaptive and Visually Switchable Adhesive Hydrogels for 3D Printing with On-Demand Detachability

Functional hydrogels with on-demand detachability and a visually intelligible adhesion switch hold significant promise for wound healing, biomedical diagnostics, and wearable sensors. Conventional hydrogels offer desirable properties such as flexibility, biocompatibility, and tissue-like mechanical properties. However, developing multifunctional hydrogels that integrate skin-conformable adhesion, controllable detachment, visual adhesion switching via tunable transparency, body-temperature responsiveness, and excellent biocompatibility remains challenging. Inspired by octopus suckers and leveraging hydrogen-bond-driven adhesion between monomers, we fabricated a hydrogel with suction-cup-like structures using vat photopolymerization-based 3D printing. The resulting hydrogel exhibits strong, reversible adhesion, with adhesive strength varying with temperature. Simultaneously, its tunable optical properties enable visual monitoring of adhesion through transparency changes. Specifically, the hydrogel adheres firmly to human skin at body temperature to aid wound healing. Upon recovery, it detaches cleanly by heating to 50 °C, leaving no residue and minimizing skin damage. Moreover, the hydrogel demonstrates excellent biocompatibility, with cell survival exceeding 98%, and antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus, with inhibition zones of 14 mm and 24 mm. In summary, this bioinspired 3D-printed hydrogel unites skin-adaptive adhesion, visually switchable adhesion, high biocompatibility, and on-demand detachability, offering great potential for advanced wound care, wearable electronics, and intelligent medical patches.