A Concurrent Plantar Stress Sensing and Energy Harvesting Technique by Piezoelectric Insole Device and Rectifying Circuitry

Concurrent high force detection accuracy and extended battery lifetime are strongly expected in wearable gait monitoring systems, which are essential for many Internet of Health Things (IoHT) applications. In this article, a piezoelectric insole device and a rectifying circuitry-based technique is presented to achieve these two ultimate goals. Here, walking induced positive and negative charges are separated for plantar stress detecting and energy harvesting, respectively; these two functions are realized concurrently. Experimental results demonstrate that first, the high detection sensitivity of 55 mN and responsivity of 231 mV/N are achieved, satisfying the need for diagnosing various diseases; second, the electric energy of 9.6 pJ (2.67×10-15 W·hr) is stored during a walking cycle, showing the potential of extending the battery lifetime. The developed technique enhances the development of gait monitoring in IoHT.