Mechanoluminescence (ML) is a type of luminescence that can convert the mechanics into light. Because of its unique characteristics, such as mechanics visualization and spatial resolution, ML provides novel thoughts to deal with the critical problems in mechanics sensing. To grasp and master the essence of ML and guide its future design and applications, it is required to understand the intrinsic physical process.

In a study published in Nano Energy, Prof. WANG Zhaofeng’s group at the Lanzhou Institute of Chemical Physics of the Chinese Academy of Sciences reported a novel non-piezoelectrical ML system, Sr₃Al₂O₅Cl₂:Ln (SAOCL; Ln=Eu²⁺, Tb³⁺, Ce³⁺). These materials have high crystal symmetry with no ML in the form of powders or the composite with hard epoxy resin. However, intense ML with tri-color can be obtained when the materials were embedded into polydimethylsiloxane (PDMS).

The ML of SAOCL/PDMS is trap-independent with unique temperature-modulated self-recoverable activity, which suggests that there should be self-activation during ML, namely, the electrons in the structure could be self-activated to the excited levels under mechanics stimuli.

To further make clear the mechanics-excitation processes, the researchers proposed an interfacial triboelectrification-induced electron bombardment model by analyzing the thermoluminescence, triboelectricity and matrix effects. The consistency between the ML and cathodoluminescence provides direct evidence for the above mechanism.

Besides, the ML of SAOCL/PDMS exhibits thermal stability that the conventional ML materials do not possess. By utilizing the trap-independent, self-recoverable and thermally stable behavior of the ML of SAOCL/PDMS, the researchers developed two types of advanced devices in terms of the visualized temperature sensing and the multi-mode information storage.

This work showed a deep understanding of the non-piezoelectrical ML from fundamentals to applications.