Pressures monitored by 3D printed capacitive pressure sensor embedded on prosthetic upper-limb socket; a case study

Abstract

The comfort fit of a limb prosthetic socket is one of the most important considerations for developing the socket for an amputee. The pressure at the touchpoint, which is the interface between the residual limb with natural skin and the prosthetic limb socket with a polymeric material, should be monitored precisely when fabricating the comfort fit. Even a small volume or shape discrepancy between the residual limb and prosthetic limb sock causes several problems in the residual limb, such as skin breakage, tissue irritation, and associated pain. Volume variations of the residual limb due to squeezing by a prosthetic limb sock result in pressure changes that can be detected using a pressure sensor. In this study, the interface pressures between the residual limb and prosthetic upper-limb socket were obtained using a 3D printed capacitive pressure sensor. An upper-limb prosthetic socket and capacitive pressure sensor were fabricated using a dual nozzle 3D Fused Deposition Modelling technique. Polylactic acid, polylactic acid-carbon black compound, and polyurethane were used as the personalized upperlimb socket and sensing electrode, and substrate material, respectively. The as-fabricated sensors were embedded into the sock wall, and their sensing properties were characterized. For a case study, the sensor-embedded sockets were worn on an amputee's residual upper-limb to characterize empirically the contact pressure occurring at the interfaces. A weight was attached to the end of the limb socket to examine the effects of weight on the local pressures acting on the residual upper limb. The observed interface pressures and pressure distribution at the interface can provide valuable information to clinicians and developers that can guide fit improvements.