Investigation of Polymer Thick-film Piezoresistors for Medical Wrist Rehabilitation and Artificial Knee Load Sensors

Readily-available and low-cost commercial polymer-based composite materials, such as standard epoxy-fibreglass printed circuit board (PCB) substrates and resin-carbon thick-film piezoresistors, were evaluated as a solution for medical force sensors, such as a wrist rehabilitation device and an implantable wireless artificial knee force sensor. We show that such materials have high sensitivity, and sufficient short-term stability – provided careful mechanical design and materials selection are made - to allow fabrication of low-cost, robust sensors, with low processing temperatures compatible with electronics integration. Example load- sensing applications are a multi-axis wrist rehabilitation device and a knee prosthesis.