Towards the Implementation of a Wirelessly Powered Dielectric Sensor With Digitized Output for Implantable Applications

Abstract

This article proposes a wirelessly powered dielectric sensor for industrial and medical applications. The sensor includes a 5-bit binary-weighted capacitor bank and an energy-harvesting rectifier realized as an integrated circuit (IC). With an automated algorithm, the capacitor bank is adjusted to counterbalance the influence of the dielectric material under test. The digitized values of the capacitor bank offer a quantitative measurement of the dielectric constant. The IC was fabricated in 180-nm CMOS process, and the control algorithm was implemented in a discrete microcontroller. The rectifier adopts a differentially cross-connected topology which achieves the rectification efficiency around 72%–82%. The proposed system is used to measure the volume of phosphate-buffered saline (PBS), in which the sensor is placed under the petri dish with PBS samples. This work shows promise for implantable applications such as bladder urine monitoring and other body fluid analysis.