Stretchable Optical Fibers: Threads for Strain-Sensitive Textiles

Soft, stretchable, sewable, and strain-sensitive optical fibers are reported. Intrinsically stretchable optical waveguides capable of >100% strain are formed by coating a commercially available elastic urethane fiber (Stretch Magic) with a silicone cladding having a lower refractive index. These 1-2 mm diameter fibers can be attached to textiles using a sewing machine. Because the attaching threads create microbends in the fiber, the sewn fibers are prestrained for monotonic intensity-versus-strain behavior. Installed in a stretchable piece of athletic tape, they detect strains originating from changing muscle shapes during weight-bearing activity.