The Internet-of-Things (IoT), the interconnecting of everyday devices and objects embedded with electronics, software, and sensors and enabling them to send and receive data, has accelerated the demand for development of wearable technologies that can be used to enhance or monitor the human body and respond to various environments, such as fitness trackers and smart clothing. Concomitant with IoT advancements, smart textile technologies are increasing in popularity because they offer the potential to combine real-time personal communication with convenient portability and can detect and react to environmental variations in light intensity, temperature, and pollution levels when integrated into clothing. For example, smart clothing could become warmer in order to keep the wearer warm when the environment is too cold, and vice versa. Light-emitting textiles are also getting increased attention as they can be used in high-visibility outfits for personal safety, such as for joggers in dark areas, pedestrians at night, and for attractive signaling that enables mutual recognition or new forms of communication.
Here, we integrated zinc sulfide-embedded polydimethylsiloxane into a mechanoluminescent fiber that can be used as a wearable light-emitting textile. The fiber is made robust by increasing the strength of the binding of the mechanoluminescent materials with a chemically treated cross-shaped fiber frame and employing an adhesive layer for encapsulation. This prevents irregular failure induced by the creation of defects (e.g., crevice, bubble) and stable mechanoluminescence behavior has been achieved for over one hundred thousand cycles. Further, by incorporating an encapsulating layer, the mechanoluminescent fiber is highly resistant to water and detergent. A mechanoluminescent fabric made by weaving mechanoluminescent fibers, and which is potentially adaptable to wearable light-emitting fabrics powered solely by human motions such as body movement and muscle stretching, has also been developed. From an application perspective, the mechanoluminescent fibers are promising candidates particularly for wearable displays in high-visibility outfits for personal safety because of their sensing and display functions. Battery-free, human motion-powered mechanoluminescent textile is expected to enable environmentally friendly and sustainable light, and paves the way for new approaches to wearable devices that reduce energy waste.
 S. M. Jeong, S. Song, H. –J. Seo, W. M. Choi, S. –H. Hwang, S. K. Lim, Advanced Sustainable Systems 1, 1700126 (2017).