Glucose Level Sensing Using Single Asymmetric Split Ring Resonator

Abstract

In this article, a biosensor composed of a single metamaterial asymmetric resonator is specifically designed for sensing the glucose level of 1 µL of solution. The resonator has two gaps, and one of them ends with a semicircle shape on which the glucose solution is placed. This design helps in confining the drops of glucose solutions in a specific area where the field is maximally confined in order to enhance the electromagnetic wave-matter interaction. Six samples of glucose solutions with concentrations that cover hypoglycemia, normal and hyperglycemia conditions that vary from around 41 to 312 mg/dL were prepared and examined by this biosensor. The resonance frequency redshift was used as a measure of the changes in the glucose level of the solutions. Without glucose solution, an excellent agreement between the measured and simulated transmission amplitude was observed. The increase in glucose concentrations exhibited clear and noticeable redshifts in the resonance frequency. This biosensor revealed a 0.9997 coefficient of determination, which implies an excellent prediction fitting model. More importantly, a sensitivity of 438 kHz/(mg/dL) was observed over the range of concentrations of the aqueous solution.

Excitation of Asymmetric Resonance with Symmetric Split-Ring Resonator

“…This topic was thoroughly discussed in a recent paper [ 55 ]. Therefore, in order to provide a fair comparison, a sensitivity analysis was carried out for the asymmetric double split ring resonator (aDSR) that provides excitation of Fano-like resonance, which has been the subject of many papers [ 28 , 29 , 47 , 49 ]. The dimensions of the aDSR were optimized such that the resonance frequency was almost the same as that of the current design.…”

“…It is always desirable to reduce these amounts in order to reduce the associated losses that can lead to the broadening, or even the disappearance, of a resonance. As an example, the authors of [ 49 ] successfully used 1 μL glucose solution to differentiate between different glucose level concentrations.…”

“…Various designs have been proposed across the electromagnetic spectrum based on the above approaches, utilizing conventional metal resonators on a dielectric substrate with electric field excitation or complementary structures with magnetic field excitation following the Babinet principle [ 45 , 46 ]. Furthermore, the excitation of symmetric and asymmetric resonances was reported not only using metasurfaces with a large number of resonators, but also with a single resonator inside a rectangular waveguide system [ 47 , 48 , 49 ]. As a result of the coupling between the resonator inside the waveguide and its mirror images that were enabled by the metallic walls of the waveguide, the collective behavior of the full metasurface was achieved [ 50 , 51 , 52 ].…”

Feasibility Evaluation of Metamaterial Microwave Sensors for Non-Invasive Blood Glucose Monitoring

“…The computational domain geometry includes one of the sensors—MTM9 and MSTL, whose geometries are described in detail in [ 22 ]. For readers’ convenience, partially transparent models revealing the internal structures of MTM9 and MSTL are depicted in Figure 1 A and 1B, respectively.…”

“…In most cases, microwave blood glucose sensors are designed to change their resonant frequency in direct proportion to changes in tissue dielectric parameters. Some investigators use a patch antenna or various types of microstrip lines for glucose detection [ 20 , 21 , 22 , 23 ]. Unlike resonance-based sensors, antennas can alternatively be based on the principle of modulating the amplitude and phase of S-parameters.…”