Optically Instrumented Insole for Gait Plantar and Shear Force Monitoring

In this work, a fiber Bragg gratings (FBGs) based sensing insole, capable of simultaneously measure plantar force (PF) and shear force (SF) is proposed. The insole has four measuring points, strategically located for a full gait analysis. Each sensing point contains a sensor-cell which consists of a polylactic acid (PLA) structure, covered by an epoxy resin layer, and crossed by one optical fiber with two FBGs, FBG1 and FBG2, respectively. Due to the specific design of the system, the FBG1 is sensitive to both forces (with higher sensitivity to the PF), while the FBG2 is designed to detect only the SF. The instrumented insole was tested during static and gait exercises, and the results, obtained for the PF and SF monitoring, were according to those theoretically expected.