## 3 Results and Discussion
### EIS Measurements
We observed very close results for all three EOs (0.8045, 0.7088, and 0.7307 for tea tree, clary sage, and cinnamon, respectively), indicating that the proposed platform is suitable for all three tested EOs. Finally, using measuring data at a frequency of 5 kHz, which was not included in the initial data fitting, relative errors were determined--0.299, 0.026, and 0.307% for tea tree, clary sage, and cinnamon, respectively. Additionally, the limit of detection (LOD) and the limit of quantification (LOQ) were calculated and the results are presented in Table 1. They were calculated as follows: LOD = 3.3 * (standard deviation of the Y-intercept of regression line/slope), LOQ = 10 * (standard deviation of the Y-intercept of regression line/slope). The modulus of impedance (electrical resistance) of textile structure between electrodes 1 and 3 was about 0.6 \(\Omega\) (confirming the good conductivity of the knitted silver thread), while the modulus of impedance was almost doubled by inserting EOs into the textile-based platform. For cinnamon oil, Z13 was about 1.3 \(\Omega\); for tea tree oil, the impedance was 1.4 \(\Omega\); and for clary sage, it was about 1.6 \(\Omega\). Figure 4 shows that a similar trend was obtained for all frequencies. The electrical conductivity of EOs is due to the presence of free charges, which move under the effect of an electric field, providing an electrical current [26]. Considering that the electrical properties of EOs depend mainly on their chemical composition, a variation can be detected due to an increase in bioimpedance when textile electrodes absorb the applied solution with different EOs. The use of different types of EOs affected the electrical performance and allowed the identification of EOs (bioimpedance), which, in combination with textile electrodes, were higher than the impedance of a dry chip. The next step of our study was to analyze if the proposed sensing platform could differentiate not only the type of EO applied but also the various concentrations of one type of EO. Figure 5 depicts the Nyquist plot for different concentrations of tea tree EO of 0.2, 4, and 10% for the pair of terminals 1 and 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**EOs** & **Linearity (R\({}^{2}\))** & 1 LOD 1 & 1**LOQ 1** \\ \hline Tea Tree & 0.8045 & 5780.43 & 17,516.40 \\ \hline Clary Sage & 0.7088 & 7515.51 & 22,774.30 \\ \hline Cinnamon & 0.7307 & 7118.50 & 21,571.20 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Limit of detection and limit of quantification. Figure 5: Nyquist plots for different concentrations of tea tree EO. Increasing the concentration of essential oil resulted in a higher electrical resistance. The reason for this behavior can be ascribed to two effects. The first one was that increasing the ratio of EO compared to ethanol and water resulted in a decreased number of ions that could participate in the current flow, which led to a decrease in the conductivity. The second reason could be due to the difference in dielectric properties. It is known that the dielectric constant (relative permittivity) of water is around 80; for ethanol, it is around 22; and for EOs, it is around 2 [27; 28]. This means that increasing the concentration of EOs will decrease the dielectric constant and consequently decrease the capacitive part of the impedance. Bearing in mind that capacitance and impedance are inversely proportional, this resulted in increasing the real part of the impedance by increasing the concentration of EO. The observed increase in resistivity from Nyquist plots is confirmed by the calculated RMSD values--34.65, 40.86, and 51.36 for concentrations of 0.2%, 4%, and 10%, respectively. Furthermore, we analyzed the change in Nyquist plots caused by increasing the time of exposure of the proposed platform to the influence of the EOs.