Mechanical characterization of a piezoelectric sensor for podiatrist applications

The analysis of plantar pressures is an integral part of the series examinations carried out by the podiatrist, it allows him to visualize the distribution of the points of support and the movements of the foot during the different phases of walking. The system used for the analysis is a podiatry treadmill composed by piezoelectric sensors which react to the applied pressure. The recorded data will be converted into force data for a correct interpretation of the results by medical specialists. This article presents a part of the development of a podiatry sole based on piezoelectric sensors manufactured at the IETR-Nantes laboratory. The mechanical characterization of an industrial sensor (7BB-35-3L0) from Murata will be presented first to validate the repeatability and the reproducibility of the measurement method, which should allow to define the transfer function relating the output of the sensor to the applied stress. A Shimadzu EZ-X series universal electromechanical test frames are used to apply pressure to the sensor, at the same time as the machine records the force data, a national instrument acquisition card is connected to the sensor to collect his signal. Two methods are tested for the processing of the recorded data, the results obtained make it possible to validate a method which gives a constant coefficient representing the transfer function, thus leading to the final objective which is to characterize the flexible piezoelectric sensors manufactured at the IETR laboratory.