Synergy between Defects and Lattice Distortion Drives Self-Powered Elastico-Near-Infrared Mechanoluminescence in Cr3+-Doped Spinel Oxides.

Abstract

Elastico-mechanoluminescence (ML) enables unique force-to-light transduction for applications in human-machine interaction and smart sensing, yet traditional trap-controlled models fail to explain self-powered ML phenomena. Here, a Cr³⁺-doped spinel oxide exhibiting autonomous near-infrared (NIR) ML is reported, where self-powered emission originates from synergistic interactions between local lattice distortions and multi-defect networks. Theoretical calculations reveal that Cr³⁺ doping activates nearest-neighbor sites to generate mid-gap states, facilitating stress-driven electron tunneling to luminescent centers without external excitation. The material shows narrowband NIR emission (711 nm) from the spin-forbidden transition, with linear ML intensity response to mechanical stress and negligible persistent luminescence. Proof-of-concept demonstrations in bright-field anti-counterfeiting (NIR QR-code imaging) and biomedical tissue penetration (10 mm pork) validate its practical utility. This work establishes a defect-distortion coupling mechanism for self-powered NIR-ML, providing a theoretical framework to guide the design of next-generation autonomous optomechanical materials for energy-efficient sensing and bio-imaging.