Flexible Matrix Composite Wafers in Smart Prosthetic Sockets for Improved Socket Comfort and Fit

Abstract Improving comfort is a paramount objective in the design process of a lower-limb prosthetic socket. A common issue with maintaining a comfortable socket fit during the day is that volume changes in the residual limb can result in regions of severe discomfort on the limb. These changes in residual limb volume can occur during both brief and long-term timescales. The objective of this research is to develop smart prosthetic sockets that can adjust for changes in the volume of the residual limb. Flexible Matrix Composites (FMCs) are high performance actuators that exhibit a high mechanical advantage when internally pressurized. FMCs are composed of symmetric layers of carbon fiber surrounding a flexible rubber tube. The actuators are then coiled into custom molds and filled with an elastomer, thus forming the active wafer. While FMCs are typically used for axial actuation, the FMC wafers take advantage of the radial expansion of the actuator to obtain actuation through the thickness of the wafer. Previous research characterized the effect of several design variables on the stiffness and actuation performance of wafer-style FMC actuators. Building upon the previous work, custom FMC wafers are fabricated and integrated into prosthetic sockets, thus forming a smart socket that can accommodate for volume changes. A socket was fabricated with custom wafers designed to target critical regions identified for the participant. An external gas canister and pressure regulation valve was used for precise control of the air pressure within the wafers. The participant was subjected to a physical activity regimen, recording their socket comfort every 150 seconds. The participant’s socket comfort score improved using the FMC wafers after actuation.