Dual-Wavelength Responsive Hydrogel Glue with Visible-Light Bonding and UV-Triggered Debonding via Ortho-Nitrobenzyl...

Removable adhesives with controllable bonding and debonding capabilities are essential for biomedical devices, temporary fixation, and recyclable materials. Here, a dual-wavelength hydrogel glue is presented that integrates visible-light polymerization (470 nm) for strong adhesion and UV-induced degradation (365 nm) for rapid debonding. The system leverages camphorquinone as a visible-light photoinitiator and ortho-nitrobenzyl poly(ethylene glycol) dimethacrylate (ONB-PEGDMA) as a UV-cleavable crosslinker, ensuring independent control over adhesion and detachment with orthogonal polymerization and degradation. The degradation rate of ONB-PEGDMA increases proportionally with light intensity, providing precise control over cleavage kinetics, with first-order rate constants of 0.155, 0.278, and 0.669 min^-1 for 20, 50, and 100 mW cm^{- 2}, respectively. The hydrogel exhibits strong adhesion (≈200 kPa) and undergoes a fourfold reduction in adhesion strength within 90 s of 365 nm irradiation at 100 mW cm^{- 2} under a constant tensile load of 10 N, enabling efficient removal. Rheological analysis confirms a significant decrease in storage modulus and crosslinking density after UV exposure, leading to network softening and structural failure. This work pioneers a phototunable hydrogel glue that bridges photopolymerization and photodegradation, offering a promising platform for next-generation adhesives with precise spatiotemporal control and with easy application, good bonding, and rapid UV-triggered debonding.