Polymer-based flexible capacitive pressure sensor for non-invasive medical monitoring applications

In this paper, the design, the fabrication and the electromechanical characterization of polymer-based flexible pressure sensor are presented. This kind of sensors is developed for the non-invasive monitoring of pressure/force distributions that is required in many medical applications such as the monitoring of plantar pressures or chronic venous disorder treatments. The sensors considered in this paper are of a capacitive type. They are composed of two millimetric copper electrodes, separated by polydimethylsiloxane (PDMS) dielectric layers and deposited on a Kapton substrate. A study of the deformation of PDMS thin films under normal stress is carried out by finite element computations as well as experiments. This study points out a sensor design optimization parameter, the form ratio of the indented PDMS layer, which is used to design and fabricate capacitive micro-sensors samples. Preliminary electromechanical characterizations of realized sensor samples validate the approach. Under a 10 N normal stress, the sensitivity of 9 square mm sensors varies from 3% up to 17% in capacitive change, according to the chosen form ratio of the used PDMS layer.