Flexible Smart Insole and Plantar Pressure Monitoring Using Screen-Printed Nanomaterials and Piezoresistive Sensors

Abstract

Individuals experiencing gait dysfunction─such as the elderly, those with peripheral nervous system damage, or individuals with Parkinson's disease─face a heightened risk of physical injury due to imbalanced weight distribution. Despite recent advancements in wearable movement trackers, there remains a significant need for a reliable long-term plantar pressure monitoring system. While some existing devices measure pressure characteristics, many are hindered by limitations in spatial resolution, sensitivity, and the presence of bulky peripherals. Here, we introduce a flexible smart insole system that integrates screen-printed nanomaterials to create a high-density piezoresistive sensor array, enabling accurate plantar pressure measurement during daily activities. To ensure scalable and cost-effective manufacturing, we utilize a screen-printing method to fabricate 173 carbon-based sensors directly onto a flexible insole circuit. The printed sensors demonstrate a remarkable sensitivity of -0.322 kPa^-1, surpassing previous benchmarks. When combined with a wearable mobile communication circuit, this system offers a comprehensive analysis of the user's plantar pressure distribution. Experimental studies conducted with human subjects showcase the smart insole's real-time monitoring capabilities in common daily ambulation scenarios. The integration of high spatial resolution, exceptional sensitivity, and a fully mobile wearable system holds significant promise for enhancing outcomes across various applications, from healthcare to athletics.