Polymer optical fiber-embedded, 3D-printed instrumented support for microclimate and human-robot interaction forces assessment

Abstract

This paper presents the fabrication, characterization and applications of a 3D-printed instrumented support for wearable devices. Intensity variation-based polymer optical fiber (POF) sensors were employed in the support instrumentation, in order to obtain a low-cost system. In the proposed instrumented support, two POFs are embedded in a 3D-printed acrylonitrile butadiene styrene (ABS) rigid structure for microclimate assessment (without the influence of the applied force). Additionally, other two POFs are embedded in a thermoplastic polyurethane (TPU) flexible structure for the force assessment, where one sensor measures the applied force in flexion cycles and the other in extension cycles. All four sensors are characterized with respect to temperature and humidity. Both force sensors are also characterized with respect to the force and their cross-sensitivities with respect to the temperature and humidity. The results show the feasibility of the proposed sensor system embedded in the 3D-printed support, where the errors for the force assessment are below 2.8 N, and for temperature and humidity the errors are about 1.1 °C and 2.5%, respectively. The feasibility of the proposed instrumented support in measuring force and microclimate variations was also verified in the application as a shank support for a lower limb exoskeleton for knee rehabilitation and on a passive orthosis for gait assistance.