Photopatterned Tribo‐Mechanoluminescent Hydrogel for Self‐Powered Multimodal Sensing and Underwater Optical SOS Signaling

ABSTRACT Operating flexible sensors in diverse environments, especially underwater with limited power and communication, remains a significant challenge. Herein, we present a photopatterned tribo‐mechanoluminescent (TML) hydrogel that integrates stress‐induced luminescence and triboelectricity into a single, multifunctional platform. The device is fabricated in one step using a customized photomask, which simultaneously structures the hydrogel electrode and embeds colorful, predefined luminescent patterns. Upon mechanical stimulation, the device generates a synchronous electrical output as a triboelectric nanogenerator (TENG) with an open‐circuit voltage of 82 V, while also providing an instantaneous visual optical response, enabling dual‐mode sensing without an external power supply. We quantitatively investigated the correlation between light emission intensity and applied force, as well as UV exposure conditions. Leveraging these dual outputs, the TML hydrogel achieves excellent performance in multimodal motion monitoring and, more importantly, serves as a self‐powered underwater distress beacon. The visual SOS pattern offers a clear optical signal for rescue identification, while the synchronous electrical pulses can be transmitted to remote receivers via connecting cables. This work provides a new strategy for designing intelligent, self‐powered systems for emergency rescue and human–machine interaction in austere environments.