Piezoelectric-Based Insole Force Sensing for Gait Analysis in the Internet of Health Things

Insole gait analysis has become a research focus in recent years, owing to its potential in sports training improvement, and real-time and long-term health status monitoring. Among diverse insole gait analysis technologies, piezoelectric-based techniques receive growing attention, due to its nature in converting force to electric signals, potentially ensuring long-battery lifetime compared to its counterparts. However, current literature mainly reports on the detection of 6-8 main plantar positions for motion interpretation, lacking in providing enough information for illness diagnosis, e.g., hip disease. In this article, smart integration of piezoelectric films with different polarization orientations and 32 electrodes is presented, for supporting both normal and shear stress detection with high three-dimensional resolution. High sensitivities at 56 and 173 mN are demonstrated experimentally for normal and shear stress sensing. With our comprehensive algorithms, accurate and real-time gait monitoring for the majority parts of the plantar area is obtained. This paper can support diverse utilization purposes, advancing the area of insole gait analysis.