Mechanically Robust Biopolymer Optical Fibers with Enhanced Performance in the Near-Infrared Region

Polymer optical fibers (POFs) are lightweight, fatigue-tolerant, and suitable for local area networks, automobiles, aerospace, smart textiles, supercomputers, and servers. However, commercially available POFs are exclusively fabricated using synthetic polymers derived from nonrenewable resources. Recently, attempts have been made to fabricate biocompatible and biopolymeric optical fibers. However, their limitations in mechanical performance, thermal stability, and optical properties foil practical applications in waveguiding. Here, we report a comprehensive study of the preparation of biopolymer optical fibers with tailored mechanical strength, thermal properties, and their short-distance applications. Specifically, we use alginate as one of the key components with methylcelluloses to promote readily scalable wet spinning at ambient conditions to fabricate 21 combinations of composite fibers. The fibers display high maximum strain (up to 58%), Young's modulus (up to 11 GPa), modulus of toughness (up to 63 MJ/m³), and a high strength (up to 195 MPa), depending on the composition and fabrication conditions. The modulus of toughness is comparable to that of glass optical fibers, while the maximum strain is nearly 15 times higher. The mechanically robust fibers with high thermal stability allow rapid humidity, touch sensing, and complex shapes such as serpentine, coil, or twisted structures without losing their light transmission properties. More importantly, the fibers display enhanced optical performance and sensitivity in the near-infrared (NIR) region, making them suitable for advanced biomedical applications. Our work suggests that biobased materials offer innovative solutions to create short-distance optical fibers from fossil fuel-free resources with novel functionalities.