Fig. 3

Adhesion properties of multifunctional hydrogels. A Schematic illustration depicting the potential adhesion mechanism between the hydrogel and the skin’s epidermis. B Photographs demonstrating the robust skin adhesion of the hydrogel. No residues or skin irritation were observed even after 10 cycles of repeated adhering-stripping processes. C Adhesion strength of the PT-DA/PAA hydrogels as a function of PT-DA concentrations against porcine skin. D Adhesion strength of the multifunctional PPGP (PT-DA/PAA/rGO-PDA) hydrogel as a function of rGO-PDA concentrations (with PT-DA concentration fixed at 2 wt%). E Adhesion strengths of the multifunctional hydrogels (PT-DA content: 2 wt%, rGO-PDA content: 0.05 wt%) on various substrates, and F their cyclic adhesion performance. G Photographs showing the adhesion capability of the multifunctional PPGP hydrogel on a wide range of substrates with varying surface roughness and wettability. H Photographs illustrate the PPGP hydrogel’s strong attachment to finger skin without interfacial detachment even during significant stretching (300% strain). I A comparison of skin adhesion strength and strain sensitivity (GF) between the PPGP hydrogel and previous hydrogels. The data were analyzed using one-way ANOVA and Tukey’s multiple comparison test (n = 7, ***p < 0.001)