Integration of ZnS:Mn²⁺ Microparticles into Electrospun PVDF-Based Nanofibers for Enhanced Mechanoluminescence

Incorporating mechanoluminescent (ML) materials into piezoelectric polymer nanofibers enables the development of advanced pressure sensors and human-machine interactive devices by providing mechanical flexibility and enhancing processibility. This study demonstrates that introducing water during the electrospinning process significantly improves the piezoelectric properties of polyvinylidene fluoride (PVDF)-based polymers, attributed to the enhanced formation of piezoelectrically active β-phases. A biphasic relationship between piezoelectricity and water concentration was revealed, with an optimal water concentration of 4 wt.% for both polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). Furthermore, the inclusion of water in the electrospinning solution facilitates the integration of ZnS:Mn²⁺ mechanoluminescent microparticles into the polymer fibers, resulting in fibrous composite membranes with significantly enhanced mechano-optical responses. After thermal annealing, the fibrous membrane by electrospinning PVDF-TrFE and ZnS:Mn²⁺ microparticles with 8 wt.% water addition demonstrated the best ML performance with high light emission intensity and reduced pressure threshold down to 18 kPa. This exceptional performance can be attributed to the local electric field generated by the encapsulation of microparticles within the PVDF-TrFE fibers, which facilitates electroluminescence and subsequently boosts the overall light emission.