Surface Plasmonic Feature Microwave Sensor with Highly Confined Fields for Aqueous-Glucose and Blood-Glucose Measurements

This article proposes a method of using a highly efficient spoof surface plasmon polariton (SSPP) endfire sensor for monitoring of aqueous glucose solutions and on-body glucose measurements. Occupying an area of around (52 mm $\times24$ mm), the proposed sensor radiates an endfire beam into a glucose water solution with a substantially reduced effective aperture. At the coplanar waveguide (CPW) port of the sensor, a pair of triangular ground planes was added to suppress the sidelobes, which have been proven to be counter-productive in glucose sensing. The slow-wave nature of the proposed SSPP endfire sensor has further advantageously enabled the glucose concentrations to be measured with an increased sensitivity. The guiding body of the sensor was designed to simulate an electromagnetic beam propagating in a dense dielectric medium with a group velocity comparable to the phase velocity of light propagating in a glucose solution. Consistent with the results of our analysis, the experimental results of this work revealed that the gradual transition of slow electromagnetic wave from the SSPP endfire sensor to the glucose water solution has successfully enabled the glucose concentrations of a solution to be measured and displayed in the form of highly observable resonant frequency shifts in S 11 parameters. The proposed design has achieved a high sensitivity of 150 MHz/mgmL-1 during on-body measurements.