Color‐Resolved Stress Sensing Visualization Based on Ratiometric Mechanoluminescence: A Universal Strategy via Radiative Energy Transfer

ABSTRACT Ratiometric mchanoluminescence (ML) methods have been recognized as a superior alternative for stress sensing over absolute‐intensity based ones in terms of sensing stability as well as visualization. This study proposes a universal strategy to realize the ratiometric ML for visual stress sensing by coupling UV ML materials with commercial LED phosphors, where the radiative energy transfer affords the multi‐color ML and the distinct excitation power‐intensity relationship for various LED phosphors enables the stress‐dependent ML color variation. As a proof of concept, a newly‐developed UV ML material, Sr 2 Al 2 SiO 7 :Ce 3+ , is incorporated with various commercial LED phosphors (e.g., CaAlSiN 3 :Eu 2+ , K 2 SiF 6 :Mn 4+ ) to fabricate a series of flexible ML composites. The resulting devices exhibit pronounced color variations upon increasing mechanical stress, allowing for visual stress distribution imaging based on color evolution. This work not only introduces a novel UV ML material, Sr 2 Al 2 SiO 7 :Ce 3 + , as an efficient mechanical‐to‐optical transducer, but also establishes a generalizable platform for designing flexible, color‐tunable ML composites using the vast repository of existing commercial phosphors.