Fiber, renowned for its breathability, flexibility, and durability, emerges as an optimal substrate for wearable devices, seamlessly integrating technology into clothing. Among the myriad applications, color-changing fibers stand out as an interface bridging humans and computers, promising advancements in communications, navigation, healthcare, and the Internet of Things (IoT).

Drawing inspiration from photochromic and polymer optical fibers, researchers from Huazhong University of Science and Technology and Nanjing University have engineered a groundbreaking multicolored, uniformly luminescent, photochromic fiber. Utilizing a mass-producible thermal-drawing method, the scientists achieved versatility in designing fiber structures, heralding a new era in wearable technology.

Unlike commercial light-emitting fibers plagued by transmission losses and artificial defects, the newly devised photochromic fiber ensures uniform brightness in light transmission, thanks to independent waveguides meticulously integrated within the fibers. By employing polymethyl methacrylate (PMMA) for the light-guiding inner layer and incorporating fluorescent composite material in the outer layer, the coaxial structure facilitates total internal reflection, harnessing the wavelength conversion effect to achieve comprehensive light emission.

The ingenious design enables precise control over color modulation within a single fiber by segmentally adjusting the brightness of coupled core layers, capitalizing on the saturable absorption effect to mitigate excessive light leakage. Through optimization of fiber structure and RGB color mixing principles, the researchers expanded the color spectrum, encapsulating multiple light-guiding core layers and fluorescent materials with different hues, thus enhancing color regulation and optimization capabilities.

To safeguard functional materials and ensure durability, stable thermoplastic polymer material is seamlessly integrated into the fiber’s exterior, providing sealing and protection.

“These fibers offer seamless integration into daily wear through conventional sewing and knitting techniques, offering a revolutionary pathway to flexible, wearable, interactive interfaces,” the researchers commented. “This breakthrough not only addresses privacy concerns but also paves the way for transformative applications in smart cities, smart homes, human-computer interfaces, and health monitoring.”

The industrial thermal drawing process allows for the preparation of up to 100 meters of luminescent fibers, overcoming the limitations of traditional methods with extended cycle times and high costs. The method is poised to meet the burgeoning demand for photochromic fibers within the textile industry, fueling innovation in wearable technology.

By Impact Lab