P-MAPS: A Custom-Topology Velostat Insole for Pressure Redistribution in Diabetic Foot Care

Diabetic foot ulcers (DFUs) remain a major complication of diabetes mellitus, with significant human and economic costs. Plantar pressure (PP) is the most widely used surrogate to assess DFU risk. Existing PP measurement insoles are primarily designed for in-clinic assessments using external instrumentation to guide passive offloading strategies. However, reliance on brief clinical measurements limits their ability to capture real-world loading patterns, motivating the development of sensing systems capable of continuous monitoring and integration within pressure-management footwear. Such systems require spatially discretized sensing elements fully embedded within the shoe architecture. This work presents the design and characterization of P-MAPS (Plantar-Monitoring Au-Plated Pressure System), a custom-topology pressure-sensing insole co-designed for precise spatial alignment with offloading elements. The sensor uses the piezoresistive response of Velostat combined with gold-plated electrodes to improve uniformity and repeatability. The device exhibits a measurement range of 45–350 kPa, a coefficient of variation below 2.5%, normalized hysteresis of 25.8%, and 6% drift after 5 min. Dynamic gait validation against a commercial reference (Pedar, Novel) demonstrated accurate peak-pressure estimation with 2.6% error under full spatial overlap, while enabling localized pressure measurement over actuated regions and revealing that sensing areas not co-located with actuator regions can misrepresent local pressures due to spatial averaging effects. These results establish P-MAPS as a robust and practical sensing solution for continuous, footwear-integrated plantar-pressure monitoring and adaptive offloading applications.