Bioinspired optical fiber sensor for simultaneous shear and vertical forces monitoring

This work reports the development of a bioinspired sensor capable of measuring vertical and shear (tangential) forces. The sensor is composed of two materials, the polylactide (PLA) and epoxy resin, combined with a photosensitive optical fiber with two fiber Bragg gratings (FBG1 and FBG2). The FBG1 was placed in a cavity filled with epoxy resin, while FBG2 was between the cavity and the shear wall that undergoes shear force. This FBGs' encapsulation allowed one of them to be affected by vertical and shear forces (FBG1), while FBG2 was only affected by shear force. The calibration and performance tests were carried out with the aid of an electronic tri-axial force sensor. From these tests, sensitivities of K1V= 0.02±2.35x10^-4 nm/N; K1S= 0.13±3.25x10^-3 nm/N; K2V= -2.88x10^-4±6.72x10^-5 nm/N and K_2S= -1.77±0.03 nm/N to each type of force, for FBG1 and FBG2, respectively, were achieved. The obtained results demonstrated the reliability of the developed solution, with a significant improvement of its sensitivity to shear force, and a low production complexity, when compared to other previously reported optical sensors.