Flexible photonic waveguides and textiles: Materials, fabrication techniques, and emerging applications in wearable sensing

The integration of photonics with flexible materials has led to the emergence of flexible photonic waveguides and photonic textiles, which are enabling technologies for next-generation wearable sensing systems. These systems combine optical functionality with mechanical compliance, allowing seamless interfacing with the human body and dynamic environments. This review presents a comprehensive analysis of the materials used in flexible photonic platforms, including polymers, hydrogels, elastomers, and biodegradable substances, highlighting their optical properties, mechanical behavior, and biocompatibility. Various fabrication techniques such as nanoimprinting, 3D printing, fiber drawing, and roll-to-roll processing are discussed, with an emphasis on their scalability and integration capabilities. The review also explores different waveguide architectures and the incorporation of photonic elements into textiles through weaving and embroidery. The potential of photonic textiles to serve as smart garments with sensing, display, and actuation capabilities is examined. Current challenges such as optical losses, mechanical durability, power integration, and manufacturing scalability are identified. The review concludes by outlining future directions and interdisciplinary strategies needed to overcome these limitations and realize the full potential of flexible photonic systems in real-world wearable applications.