Ultrasensitive Mechanoluminescence of Pr³⁺-Doped Perovskite Oxide for 3D Strain Sensing and Visualization

Owing to the unique mechano-optical response, mechanoluminescence (ML) materials possess dynamic, sensitive, visual, and recoverable strain sensing capabilities. However, the dilemma of lacking outstanding ML materials with high detection precision under micro deformations still exists, thereby hindering advanced applications in multi-angle and multidimensional scenarios. Herein, a novel Pr³⁺-doped perovskite oxide (NaTaO₃:Pr³⁺)-based composite elastic thin film is developed, which achieves ultrasensitive ML responses to both microscale compressive and tensile strains. Compared with the record of LiTaO₃:Tb³⁺, the corresponding deformation detection limit has been improved by five times, reaching 0.01%, which is comparable to the performance of the widely used piezoresistive and capacitive sensors. The results reveal that the ML originates from the interaction between adjacent defects and the varying local piezoelectric fields near Pr_NaO₉ and Pr_TaO₆ polyhedra. Most notably, the strain and ML demonstrate identical distributions on a 3D-printed model coated with NaTaO₃:Pr³⁺ thin film even under micro deformation less than 0.4%, highlighting the significant potential of NaTaO₃:Pr³⁺ for advanced 3D microstrain sensing applications. This work provides convincing insights into the investigation of ML mechanisms through local trap and piezoelectricity analyses, along with an exemplificative application in advanced strain sensing and visualization at microscopic and multidimensional scales.