Review of state-of-the-art sensor applications using mechanoluminescence microparticles

The term mechanoluminescence (ML) refers to the light emission from various organic and inorganic materials in response to mechanical stimuli such as friction, tension, fracture, and compression. Recently, this interesting luminescence phenomenon has enabled us to explore various advanced sensor applications. In this review article, the overall ML mechanism that arises under different experimental conditions is discussed thoroughly. The recent research achievements of state-of-the-art sensors based on ML microparticles such as SrAl₂O₄:Eu,Dy (SAO), ZnS:Cu, and ZnS:Mn are then reviewed. As a new functional smart material, SAO ML microparticles can be used in possible substitutive and substantial methods for structural health monitoring (SHM) systems, owing to their relative simplicity but effectiveness in detecting arrested or propagating crack tips, and in assessing the in-situ structural state by means of fracture parameters such as stress intensity factors. The applicability of ML paint and thin films on various types of ceramics and concretes as fracture sensors is reviewed. The research on sensors based on different ML microparticles such as noncontact torque sensors based on ZnS:Cu, flexible pressure sensors and impact sensors using ZnS:Mn is also reviewed in this article. Potential applications using ML microparticles are also briefly discussed.