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

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.