Porous conductive composite-based robust smart insole with linear pressure sensitivity

Smart insoles integrating flexible pressure sensors have garnered significant attention in the fields of smart healthcare and medicine. These insoles enable real-time plantar pressure monitoring, facilitating applications such as posture correction and the early diagnosis of Alzheimer's disease and diabetic foot ulcers. Despite advancements in flexible pressure sensors, the widespread commercialization of smart insoles has been hindered by challenges including high production costs, inadequate mechanical durability, and non-linear sensitivity over the typical plantar pressure range (0-600 kPa). In this study, we successfully fabricated a porous conductive composite-based flexible pressure sensor and smart insole using simple, cost-effective methods, including extrusion and hot-pressing. By optimizing the multi-walled carbon nanotube (MWNT) concentration and foaming ratio, the sensor exhibited high sensitivity (2.92 × 10⁻⁴ kPa⁻¹) and exceptional linearity (R² = 0.99) across the typical plantar pressure range encountered during human walking (0-600 kPa). Beyond achieving high sensitivity and linearity, the smart insole exhibited outstanding mechanical durability, attributed to its monolithic device structure. The integrated smart insole consistently maintained its performance under extreme conditions, including repeated pressing, bending, and washing cycles. Moreover, this study offers novel experimental insights into the reorientation behavior of MWNTs during the foaming process, a phenomenon previously lacking empirical evidence. This innovative approach is expected to find applications in diverse fields, including smart healthcare, augmented/virtual reality (AR/VR), gaming, and sports science, offering a durable, cost-efficient, and accurate solution for real-time plantar pressure monitoring.