mechanoluminescence

Mechanoluminescence is the emission of light produced by mechanical stimulation of a material. The mechanical input can be pressure, friction, bending, tapping, scratching, or impact, and the light emission can arise from crystals, powders, thin films, or composites. Mechanoluminescence sits among related phenomena such as triboluminescence and piezoelectric luminescence, but it emphasizes the conversion of mechanical energy into optical energy through luminescent centers in a material.

The prevailing mechanism involves converting mechanical energy into electrical energy that excites luminescent centers. Mechanical stress can generate local electric fields via piezoelectric or triboelectric effects, which in turn promote radiative transitions in dopant ions (for example Mn2+, Eu2+, Tb3+) embedded in a host lattice. In some systems, luminescence is associated with surface states or with charge separation at crack tips during fracture. The precise mechanism depends on the material’s crystal structure, dopant, microstructure, and the mode of mechanical stimulation.

Materials commonly studied include doped phosphors such as zinc sulfide doped with manganese (ZnS:Mn) and various oxide or fluoride hosts containing rare-earth dopants. In addition to single crystals and powders, mechanoluminescent emissions have been demonstrated in composites and flexible films, enabling planar or wearable devices.

Applications under exploration encompass self-powered light sources, tactile displays, and structural health monitoring. Mechanoluminescent materials can visualize pressure fields, monitor strain, or provide interactive lighting without external electrical power. Challenges remain in achieving high brightness, cycling stability, and scalable fabrication, while ongoing research seeks to optimize hosts, dopants, and device architectures for practical use.