Multi-mode mechanoluminescence of fluoride glass ceramics from rigid to flexible media toward multi-scene mechanical sensors

The smart mechanical sensing technology based on mechanoluminescence (ML) has potential applications in the fields of wearable mechanical sensors and remote detection of human health due to its characteristics of non-contact, visualization, and remote signal transmission. Herein, a new strategy for multi-mode ML in a rigid and flexible medium by embedding fluoride nanocrystals (CaF2: Tb3+) in amorphous media was proposed and the intrinsic physical mechanism of energy conversion was clarified. For the rigid transparent CaF2: Tb3+ glass ceramics (GCs), without being fabricated with any special medium, recoverable trap-controlled ML can be generated under friction after X-ray pre-irradiation. Furthermore, the ML composite device fabricated using CaF2: Tb3+ GC powder and flexible stretchable polydimethylsiloxane (PDMS) can achieve self-recovery ML under multimode mechanical stimulation due to the induction of inorganic-organic interface triboelectrification. Finally, rigid accurate stress detection at non-stressed point positions is designed based on the remote transmission of a ML signal owing to the unique optical waveguide effect of GCs, and a flexible mechanical-sensing optical skin for real-time monitoring of human health status is realized by using the CaF2: Tb3+ GC powder/PDMS composite device. This work opens up a new avenue for the realization of multi-scene stress detection based on a rigid/flexible ML material. First time dual-mode mechanoluminescence in fluoride glass ceramics, transitioning from rigid to flexible media for versatile mechanical sensing.