A first approach to foot motion monitoring using conductive polymer sensors

Abstract

A study was conducted of socks fitted with thin flexible conductive polymer sensors for the potential use as a smart sock for monitoring foot motion. The thin flexible sensors consisted of a conductive polymer applied on an elastic textile substrate that exhibited a resistance change when strained. Quasi-static response tests of the basic sensor over a static load range of a few Newtons were conducted and showed a time varying response as observed by previous investigators. Dynamic testing through an electrodynamic shaker shows good dynamic response at a low frequency range, less than 4Hz. Strips of 12 cm x 1 cm of the sensor on fabric showed a reproducible basal resistance on the order of 10KOhms. Other geometries of the continuous sensors and correlation of strain to resistance variation were studied. Similar tests were performed on different textile substrates which vary in composition and microstructure, i.e. woven, knitted, nylon%, polyester%, etc... These sensors were integrated into socks and preliminary results indicate that distinct responses to different foot motion patterns are detected in sensors placed at different joint locations on the foot. Further processing of strain results from smart socks should provide information about the kinematics and dynamics of the human foot.