A Non-Invasive Flexible Glucose Monitoring Sensor Using a Broadband Reject Filter

In this paper, a novel, highly accurate, non-invasive glucose-monitoring sensor that is based on a flexible broadband reject filter is presented. The filter topology comprises a tapered feed line at a top layer that excites four open loop resonators on the bottom layer. The broadband reject response is achieved by relying on a modified log-periodic distribution of the open loop resonators. The embedded resonators are reduced in size and are designed to exhibit an enhanced sensitivity to track the variations of the glucose level across the 1.25-2.65 GHz frequency span. The proposed flexible filter is tested within in-vitro, ex-vivo and in-vivo setups. A high correlation between the scattering parameters of the proposed sensor and the variations in glucose levels is attained. Regression models are developed using experimental data obtained from healthy patients that are subjected to glucose tolerance tests. Results demonstrate less than 4% mean absolute relative difference between the reference and estimated glucose levels, and the predicted glucose levels lie 100% within the clinically acceptable zones as shown by the Clarke Error Grid analysis.