Trap‐Controlled, Recoverable, and Persistent Mechanoluminescence for Collision Early‐Warning and Mechanics Displaying Applications

Abstract The structural nondestructive, recoverable, and persistent mechanoluminescence (ML) is particularly required for mechanics‐driven displaying, imaging, and visualization applications. Inspired by the luminescent physics of the long afterglow materials, this work reports the ML of SrMg ₂ (PO ₄ ) ₂ :Eu ²⁺ by incorporating the powders into a flexible polydimethylsiloxane (PDMS). The results suggest that the ML from the SrMg ₂ (PO ₄ ) ₂ :Eu ²⁺ /PDMS is recoverable with a linear responsiveness to the applied stress/strain. Moreover, the SrMg ₂ (PO ₄ ) ₂ :Eu ²⁺ /PDMS exhibits ML afterglow (persistent ML), which could continuously emit luminescence after removing the mechanics stimulus source. The discussions from the matrix effects, the trap structure evolutions, and the piezoelectricity properties suggest that the piezoelectric field‐assisted trap‐controlled processes shall be responsible for the ML and the persistent ML, which can be further improved by co‐doping Ho ³⁺ . Based on the recoverable and persistent ML, two types of attractive applications in terms of the intelligent collision early‐warning system and the flexible displaying paper are developed, respectively. This work not only achieves the recoverable and persistent ML for representative applications, but also provides deep insight into the physical process, which should be valuable to guide future research.