# Hypersentized Metamaterials Based on a Corona-Shaped Resonator for Efficient Detection of Glucose
## 4 Numerical and Experimental Studies of the Proposed Sensor for Glucose Detection
The proposed designed structure is shown in Figure 10a. The required dimensions of the structure were fabricated based on the optimized dimension achieved in the numerical design. Additionally, the substrate length and width were chosen to be 35 mm \(\times\) 35 mm. Two coaxial test cables were connected to the metamaterial sensor via two ports, as shown in Figure 9b. Before taking measurements, the vector network analyzer (VNA) was connected to the structure through the coaxial cables and then calibration was done in three steps of the open circuit, short circuit and 50 Ohm load connector in the desired frequency range, as shown in Figure 9c. To take the reference data, a simulation and experiment were carried out with the presence of the glucose-water  
Figure 8: Effect of transmission line width on the resonance frequency of (**a**) reflection and (**b**) transmission spectra. Figure 9: Effect of the sensor layer radius on the resonant frequency of (**a**) reflection and (**b**) transmission spectra. and glucose-blood samples in the sensor layer. The test results were done in the frequency range of 1-8 GHz. Glucose-water mixtures were prepared at different concentrations of glucose, from 100 mg/dL to 500 mg/dL in steps of 100 mg/dL. The dielectric properties of the samples were measured using a dielectric probe kit. The data files obtained from the measured results were imported into simulation software to obtain the transmission coefficient (S\({}_{21}\)) in dB, in the frequency range of 1-8 GHz. The sensitivity of the proposed sensor was examined by means of the transmission coefficient value for all glucose concentrations, and the simulated results are illustrated in Figure 11a. As can be seen from the figure, when the glucose concentration in water was about 100 mg/dL, the resonance frequency shift was about 7.01 GHz. However, by increasing the concentration of the glucose, a clear shift in the resonance frequency could be seen towards the lower frequency. For instance, at 500 mg/dL, the resonance frequency was about 6.25 GHz, while in the frequency range from 1 GHZ to 1.6 GHz, a shift in the resonance frequency was observed when the glucose concentration was increased from 100 mg/dL to 500 mg/dL. The inset of Figure 11a shows the close-up for this shift. To validate the numerical results of the proposed sensor, the measured results of the transmission coefficient (S\({}_{21}\)) for the glucose-water mixtures at similar concentrations was recorded, as depicted in Figure 11b. The measured results showed that the designed structure was very sensitive to the samples inside the sensor layer; as seen from the figure, there was a clearer shift for all the concentrations. For instance, the resonance frequency shift between 100 mg/dL and 200 mg/dL was about 1.51 GHz. This frequency shift is larger than the shifts achieved in the other similar published works in the literature. In terms of the Q-factor, the proposed structure had a superior quality factor, which was about 246 based on the measured results at the glucose concentration of 300 mg/dL in water. Figure 10: Photographs of (**a**) the proposed structure, (**b**) its two-port connection and (**c**) experimental setup. In order to verify the sensitivity of the proposed sensor, the simulation and measurements were performed with other glucose concentrations mixed with blood: 100, 200, 300, 400 and 500 mg/dL as illustrated in Figure 12. The simulated and measured results were found to be in good agreement, where there were clear shifts in the resonance frequency of both numerical and measurement results around 2 GHz and 3.5 GHz. The results had deeper peaks around \(-16\) dB. Both results indicated that the proposed corona-shaped sensor could easily detect the minimal glucose concentration in blood, which is very important for the medical and biological applications. Figure 13a shows the comparison of the simulated and measured results along with the fitted curve of the resonance frequency shift versus glucose concentration in aqueous solution.