Design of an optical fiber embedded smart artificial tendon for deformation monitoring

Abstract

Advances in materials development provide new insights on smart structures as the ones presented in this work, which consists of multifunctional artificial tendons with structural applications and the ability of measuring deformations. The tendons are produced using Flexible UV cured and Polyurethane (heat-cured) resins. Silica optical fibers were applied as intensity variation sensors to measure the deformations in the tendons. The optical fibers have an additional capability to provide a reinforcement to the bioinspired tendon structure. The mechanical capabilities of the tendons are also analyzed, with the PU tendon reaching 30% strain and withstanding stresses up to 1.0 MPa without suffering damage. The tendons are also subject in dynamic tests, where they present sensitivity to the strain rate. Using linear regressions, intensity variation rates into the 2 ∼ 2.6 × 10⁴ a.u. × s⁻¹ range are estimated with determination coefficient (R²) higher than 0.9. Similarly, in the static bending test, the variation of the power as a function of the flexion can also be approximated by a linear behavior with a R² of 0.97. Thus, the proposed approach resulted in an optical fiber-embedded biomimetic artificial tendon that can perform not only the structural behavior, but also can measure the deformations in the structure, which are important data for the control of robotic devices.