Wireless Thin Film Strain Sensing Circuit for Implantable Applications

Abstract

Recent advances in osseointegrated prosthetics highlight the need for monitoring physical phenomena within the human body. Wireless, in vivo strain sensing could be an impactful way to address the practical challenges faced by medical professionals in determining the health and healing state of prosthetics in the body. A biocompatible, wireless strain sensor is presented here based on a thin film inductor-capacitor circuit fabricated with gold and polyimide. Strain sensitive capacitors are designed and tested to confirm functionality as sensing elements. Inductors are designed for wireless readout and tested to confirm that a careful design avoided a strain response in the inductor. The components are integrated in a thin film sensor assembly with a simple but effective process flow. The wireless strain sensors are fabricated and strain tested in a laboratory environment. This provides the basis for addressing additional challenges of in vivo sensing using the described design and exploring similar thin film approaches to sensing biological phenomena.