Elastic stretchable optical fibers

Abstract

The utilization of soft materials in the design of optical systems provides opportunities for imparting these optical systems with completely unprecedented properties. This will enhance performance of systems, such as optical fibers, and enable new application scenarios. Here, we report the design, manufacture and characterization of elastic stretchable optical fibers. Analogous to conventional optical fibers, the elastic fibers consist of a high index core, made from a polystyrene-polyisoprene triblock copolymer, and a low refractive index cladding, formed by a fluorinated thermoplastic elastomer. The fibers are manufactured by co-extrusion of their constituent materials. They can be stretched to 300% strain repeatedly. Axial deformation of the fibers results in a variation of their light guiding properties. The fibers' attenuation coefficient was determined to be 0.021 ± 0.003 dB/mm, which is 2 orders of magnitude higher than for standard optical glass fibers. The high attenuation coefficient is likely due to scattering of light by air inclusions incorporated during manufacturing at the core-cladding interface. The fibers elastic modulus is 960 ± 280 kPA and their yield strength lies in the range of 2150 ± 480 kPA. The variation in intensity of guided light as a function of strain applied axially to the fibers was measured with a customized optical setup. Our experiments show that elastic optical fibers have properties that make them desirable as mechanical sensors and components in a range of other applications, provided current manufacturing shortcomings are addressed. The fibers could be used for light delivery to individual pixels of flexible deformable displays. They could be incorporated into clothing for delivery of light for display purposes or textile-integrated photonic circuits to create functional textiles. Because the fibers can stretch, the textiles or displays will be able to undergo deformation without damage or loss in performance.