Green-Orange Bi-Color Switchable Mechanoluminescent Fiber of Okra-Like Structure for Visual Signaling

Mechanoluminescence, a phenomenon to emits light under stress stimulation without requiring an electric field or power consumption, is potentially applicable in smart wearable stress-to-light sensitive devices. These current wearable light-emitting device lacks the ability to visually represent stress changes in an intuitive manner. In this study, analogous to the arrangement and cross-sectional structure of okra seeds, a mechanoluminescent fiber is developed to monitor stress changes via dual-color emissions, in which orange occurs under pressure and green occurs under tension. This fiber exhibits high luminescence response in the experimental measurement range of <12.7 kPa stress and <10% tension strain. With sufficient strength and flexibility, the fiber can be seamlessly integrated into fabrics, preserving breathability and moisture permeability while adapting to complex body deformations. It can be easily activated by human motion, thus opening up hopeful avenues for human motion tracking, interactive textiles, intelligent warning systems, and haptic command interfaces.