Mechano-Chemiluminescent Hydrogel for Sustained Stress Visualization Under Mechanical Equilibrium

Mechanoluminescent materials serve as stress-sensing platforms that emit light autonomously, featuring properties distinct from other mechanochromic materials for stress visualization. While these materials respond instantaneously to dynamic mechanical forces, visualization of stress distribution under static mechanical loads, where both mechanical and energetic equilibrium are established, remains a significant challenge in materials science, representing a critical issue in real-time continuous stress monitoring. Here, an unprecedented mechano-chemiluminescent hydrogel (^GOxGu-gel) is presented that introduces a conceptually new approach to stress visualization. ^GOxGu-gel contains glucose oxidase (GOx), which is inhibited by guanidinium (Gu⁺) ions in the network polymer through multivalent salt-bridge interactions. Mechanical stress on ^GOxGu-gel disrupts these multivalent interactions, liberating GOx to catalyze glucose oxidation, which generates hydrogen peroxide (H₂O₂) that then drives the luminol chemiluminescence. This novel mechanism successfully visualizes stress distribution under sustained static loads, addressing the key limitation of conventional mechanoluminescent materials. The luminescence can be repeatedly switched on/off through multiple stress cycles, with original performance recovered through simple substrate replenishment.