Piezoresistive Sensor Array Design for Shoe-integrated Continuous Body Weight and Gait Measurement

Wearable pedobarography is expected to bring about significant improvements in a variety of healthcare and medical domains, including portable gait analysis and monitoring, continuous weight estimation, physical therapy, prosthetic limbs, and robotics. The traditional methods use direct shoe-insole placement of force sensors to record ground-reaction-force (GRF) patterns. Since they tap only a few points under the feet, they are not suitable to collect the total applied force due to the spread-out effect. This paper presents a piezoresistive array design for a shoe-integrated sensor array to continuously measure the total GRF throughout the walk cycle. The mechanical design of the array concentrates the applied force onto optimally placed points under the shoe sole using layered, cleat-like structures that are meant to improve the reliability and repeatability of the individual piezoresisitive force sensors. The signals of the concentrated forces are processed by a shoe-integrated micro-controller to extract gait and weight information. A proof-of-concept prototype is tested with both static and walking subjects and is shown to accurately measure body weight information throughout the walk cycle.