Strain and temperature sensors made from fishing lines

Abstract

Soft and flexible sensors are demanded in a wide variety of wearables and soft-robotic applications. We designed and developed novel integrated strain and temperature sensors using super-coiled transparent polymer fibres as an optical waveguide by exploiting changes in macro-bending optical losses induced by strain or heat. Polymers used in this research such as nylon and fluorocarbon are shaped as super-coils. The customized optical couplings were designed that can sustain tension induced by axial strain force or thermal stress (entropic spring effect). A customized method of transmission and measurement of the optical signal transferred through a super-coiled polymeric waveguide was designed to reduce attenuation losses. Transmitted optical signals were recorded in the range of −65 dBm to −45 dBm. Changes in the measured transmitted optical signal were recorded and compared for transparent mono-filament nylon fibre fishing line and fluorocarbon fibre fishing line. The trends of the measured parameters registered during the testing period showed a variation of ∼2%, good linearity and repeatability, however with minor hysteresis in the range of for nylon and the range of for fluorocarbon. Limited optical characteristics of these materials were compensated and substituted by high sensitivity introduced by a small macro-bend radius. These sensing devices combine high sensitivity with large comparative strain and a wide range of temperatures. Polymers used in this research exhibit the potential for use in SCP waveguide-based soft robotic sensors. Measured reaction times validate the potential of these sensors in measurements of moderate or slow speed processes. These sensing devices also combine a simple manufacturing process that uses abundant and cost-effective materials with a wide array of potential applications.