Shear sensor for lower limb prosthetic applications

Lower limb amputees using a prosthetic device often suffer from mechanically-induced skin injuries. Shear stresses are believed to play a significant role in the formation of these skin injuries. The work presented in this paper is aimed at creating a new class of adaptive prosthetic and orthotic interfaces involving a capacitive shear stress sensor. The sensor design and transfer function are discussed. A few preliminary test results demonstrating the functionality of the sensor are also presented.

I. Introduction

IN the U.S., more than 180,000 people use an artificial leg or foot [1]. A large fraction of amputations are necessitated by complications of diabetes and atherosclerotic vascular disease. Skin irritation, ulcers, and tissue breakdown caused by mechanical loads prevent many lower extremity amputees from pursuing their vocational and recreational interests; discomfort is a common experience. This paper presents a capacitive sensor that is capable of measuring shear stresses; quantifying shear stress will increase our understanding of how friction blisters form and how to prevent them. The sensor presented here is a work in progress and this paper discusses the design process, transfer function, and preliminary bench tests.