## 3 Measurement Setup  
For experimental verification, the proposed complementary metaresonator sensor was fabricated using standard PCB fabrication technique and measured on CCEPAR AV3672D series vector network analyzer (VNA), as shown in Figure 4. The VNA is calibrated with a frequency sweep of 4 GHz to 12 GHz and a step size of 0.01 GHz. The fabricated prototype of the complementary metaresonator sensor is connected to VNA using SMA connectors, and \(S_{21}\) is measured. The measured resonance frequency of the first notch is 7.20 GHz and the second notch is 8.93 GHz, as shown in Figure 5. The percentage errors between the measured and simulated results for the first and second notch are 0.13% and 0.44%, respectively. Figure 6 shows the measurement environment for oil characterization, and a single adjustable channel automatic pipette (Dragon Lab, 10-100 \(\upmu\)L) is used to measure the quantity of oils. The quantity of each OUT is chosen 40 \(\upmu\)L to fill the Teflon container, and measurements are performed at room temperature. Measurements are taken very  
Figure 3: The phase of transmission (\(S_{21}\)) and reflection (\(S_{11}\)) coefficients for the metaresonator sensor. Near resonance frequencies, there is sudden change in phase. Figure 2: The magnitude of transmission (\(S_{21}\)) and reflection (\(S_{11}\)) coefficients for the metaresonator sensor. The first and second notches have a resonance at 7.21 GHz with notch depth \(-\)23.85 dB and 8.97 GHz with notch depth \(-\)21.57 dB. carefully to characterize the oils with dielectric constant ranges from 2.52 to 4.47. The dielectric and chemical properties of common available vegetable oils are given in Table 2. Figure 7 shows the complementary metaresonator sensor loaded with the OUT. In order to reduce the contamination of the previous OUT, the sensor is cleaned with alcohol using a cotton ball. Before the subsequent measurement, it ensures that the alcohol is evaporated and the resonance frequency of the unloaded sensor is returned to its original state. Four samples of vegetable oils are used to measure the \(S_{21}\) of the sensor as shown in Figure 8, and results are listed in Table 3. The effect of the dielectric constant of the OUT on the resonance frequencies of the complementary metaresonator sensor is shown in Figure 9.  
Figure 4: (**a**) Photograph of CYEAR AV3672D series vector network for measurement, (**b**) fabricated prototype of the complementary metaresonator sensor. Figure 5: The magnitude of transmission (\(S_{21}\)) coefficient for simulated and measured metaresonator sensor. The unloaded \(Q\) factor of the first notch is 55.38 and that of the second notch is 21.26. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Name** & **Chemical** & **Molecular** & **Iodine Contents** & **Dielectric** & **Dielectric** \\
**Name** & **Name** & **Formula** & **(gI\({}_{2}\)/100 g)** & **Constant** & **Loss Tangent** \\ \hline Corn Oil & - & - & 110 & 2.526 & 0.0566 \\ Coconut Oil & Trilaurin & \(C_{3}H_{5}(C_{12}H_{23}O_{2})_{3}\) & - & 2.83 & - \\ Olive Oil & Triolein & \(C_{3}H_{5}(C_{18}H_{33}O_{2})_{3}\) & 84 & 3.352 & 0.0331 \\ Castor Oil & Triricinolein & \(C_{3}H_{5}(C_{18}H_{33}O_{3})_{3}\) & 85 & 4.47 & 0.0322 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dielectric and chemical properties of OUT [42, 47]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Oil Under** & **Dielectric** & **Measured** & **Notch** & **Measured** & **Notch** \\
**Test (OUT)** & **Constant** & **First Resonance** & **Depth (dB)** & **Second Resonance** & **Depth (dB)** \\  & & **Frequency (GHz)** & **Depend Frequency (GHz)** & **Depend Frequency (GHz)** & **Depend Frequency (GHz)** \\ \hline Air & 1.0006 & 7.20 & \(-\)23.51 & 8.93 & \(-\)21.57 \\ Corn Oil & 2.526 & 6.72 & \(-\)18.71 & 8.22 & \(-\)20.21 \\ Coconut Oil & 2.83 & 6.64 & \(-\)18.39 & 8.12 & \(-\)20.14 \\ Olive Oil & 3.352 & 6.50 & \(-\)19.28 & 7.91 & \(-\)21.06 \\ Castor Oil & 4.47 & 6.26 & \(-\)18.43 & 7.56 & \(-\)21.11 \\ \hline \hline \end{tabular}
\end{table}