Feasibility of force detection in 3D printed flexible material using embedded sensors

For the past century, developing an understanding of human locomotion has been instrumental in advancing orthopedic medical knowledge and technology. Historically, the field of human gait analysis has relied on force plates to investigate the forces occurring between feet and contacted surfaces. A new thrust in recent years has been to investigate foot contact forces by using specialized force sensing insoles. The medical community has already benefited from initial force sensing insole designs. Despite this technological advancement, the currently existing force sensing insoles are largely "one size fits all." This presents a challenge for the medical community as an accurate and ergonomic measurement system is not available for patients with special orthopedic needs such as those with flat feet or diabetic ulcers. Introduced here is the potential solution of using soft 3D printed material, called NinjaFlex, to develop custom, ergonomic insoles which possess embedded force sensors for plantar pressure detection. In this paper, groundwork for developing such a custom force sensing insole is laid by investigating the ability to use force sensors embedded into a geometrically simplistic 3D printed structure to detect forces applied to the overall system. Three different force sensors are investigated and their ability to accurately detect force in this configuration is compared. Additionally, a simple model relating sensed force to force applied to the system is developed. The intentions of this work are to verify the feasibility of a custom force sensing insole which further benefits the medical community.