## 5 Results and Discussion
\begin{table}
\begin{tabular}{c c} \hline \hline
**Frequency (kHz)** & **Atomization Rate (mL/min)** \\ \hline
106 & 0.73 \\
116 & 2.23 \\
122 & 3.06 \\
148 & 1.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Atomization rates at different resonance frequencies, when the driving voltage is 120 V.  
Figure 9: Relationship between atomization rate and frequency. In order to verify the effect of liquid temperature on atomization rate, pure water with temperatures of 10 \({}^{\circ}\)C, 15 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 25 \({}^{\circ}\)C, and 30 \({}^{\circ}\)C was applied accordingly. The outlet diameter of the used micro-tapered aperture was 12 \(\upmu\)m, and the driving frequency of the atomizer was 122 kHz. Figure 13 shows the relationship between the atomization rate and liquid temperature. Table 5 shows the atomization rate of pure water at different temperatures under the same conditions. It indicated that under the same working conditions, the higher the liquid temperature is set, the higher the atomization rate achieved. This phenomenon can be explained as follows: when the states have the same driving signal, micro-tapered aperture, and liquid concentration, a higher temperature can lead to larger gaps and smaller attraction between the liquid's molecules. Additionally, such larger gaps and smaller attraction could further make the viscosity of the liquid decrease and the Reynolds number of the liquid increase, which weakens the flow resistances of the micro-tapered aperture. Thereby, it is easier for liquid to pass through the micro-tapered aperture and produce a higher atomization rate. Under the same conditions, the higher the liquid temperature reaches, the higher the atomization rate of the aperture achieved. In order to verify the effect of solution concentration on atomization rate, the NaCl solutions with different concentrations of 5%, 10%, 15%, and 20% were prepared, respectively. The outlet diameter of the micro-tapered aperture was 12 \(\upmu\)m. The driving frequency of the atomizer was 122 kHz, and the liquid temperature was 25 \({}^{\circ}\)C. Figure 14 shows the relationship between the atomization rate and liquid concentration. Table 6 presents the atomization rates at different concentrations of NaCl solution under the same conditions and revealed that under the same working conditions, a lower atomization \begin{table}
\begin{tabular}{c c} \hline \hline
**Micro-Tapered Aperture Size (\(\upmu\)m)** & **Atomization Rate (mL/min)** \\ \hline
8 & 0.73 \\
10 & 2.05 \\
12 & 3.06 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Atomization rate of different micro-tapered aperture sizes. Figure 13: Relationship between the atomization rate and temperature. rate is obtained as a higher liquid concentration is applied. The explanation responsible for this phenomenon is given as follows: under a state with the same parameters including the driving signal, micro-tapered aperture, and the liquid's temperature, the higher liquid concentration means a higher solute content in the solution, producing a higher viscosity of the liquid and a smaller Reynolds number of the liquid. The higher viscosity and smaller Reynolds number can further strengthen the flow resistances of the micro-tapered aperture, which makes it more difficult for liquid to pass through the micro-tapered aperture and thus generate a lower atomization rate. Consequently, under the same experimental conditions, a higher liquid concentration used here could induce a lower atomization rate of the aperture.