## 3 Results
### Antiwetting Properties of Models in Motion  
#### 3.2.1 Coupled Desorption Properties of Vibration and Wettability  
We compared the downshifts of the measured vibration frequencies before and after the impact with successive droplets to evaluate the effect of the droplets adhering to the model surface. The initialization model at \(t\) = 1000 ms was selected for analysis. The red dotted line in Figure 5 is the wave crest during vibration, and the yellow dotted line is the wave trough. The images at each moment correspond to the tag numbers from 1 to 4 in Figure 5, and the arrows in the figure indicate the direction in which the model is about to move.  
Although the model is vibrating, continuous liquid films are observed on the hydrophilic surfaces (Figure 5a). When analysis begins (corresponding to the peak at 1 in Figure 5a), the high-thickness liquid films have already existed on the surface and have overflowed to the lower surface. In about half a cycle, when \(t\) = 1010.00 ms, the device has reached its lowest point (corresponding to the trough labeled 2 in Figure 5a). Even after about a one-half-cycle oscillation (corresponding to the portion from 3 to 4 in Figure 5a), the antiwetting ability of the hydrophilic surface is still at a low level, and the wetting on its surface does not change significantly. Theoretically, the natural frequency of the resonant-speaker system can be represented by the natural frequency (\(\omega\) = \((k/m)^{0.5}\)) of the single-degree-of-freedom system. When the stiffness (\(k\)) is constant, the system mass (m) is inversely proportional to the natural frequency (\(\omega\)). The theoretical output frequency of the resonant speaker is 60 Hz, the measured amplitude when the model is in a stable state is 0.3062 mm, and the measured frequency is 28 Hz, which is 53.3% lower than the theoretical output frequency (60 Hz). This shows that the adhering water on the hydrophilic surface increases the effective mass of the model, the vibration frequency is lowered, and the amplitude of the model oscillation is significantly lessened by the substantial thickness of the liquid film (see details in \"Supporting Movie S3\" in the Supplementary Material).  
We found that the superhydrophobic surface has excellent antiwetting properties and maintains high antiwetting stability, compared with the model with a hydrophilic  
Figure 5: Multiple droplets impinge on hydrophilic and superhydrophobic vibrating aquatic-UAV models. The peaks and troughs of vibration are indicated by red and yellow dashed lines, respectively. The arrows are the vector directions of motion. From 1 to 4 represent the corresponding vibration phases. (**a**) The hydrophilic model with a deep liquid film, even under vibration. (**b**) The superhydrophobic model, and vibrations promoting liquid repellency (see details in “Supporting Movie S3” and “Supporting Movie S4” in the Supplementary Material).  
surface under vibration (Figure 5b). A large number of derived droplets are created in a full oscillation cycle, and they fall away in the next half cycle (corresponding to 3 to 4 in Figure 5b); as this process continues, the surface can maintain a long-term dry state (see details in \"Supporting Movie S4\" in the Supplementary Material). Through Fourier transform analysis, the measured amplitude of the model's oscillation is 0.3294 mm, which is 7.0% (0.3062 mm) higher than the hydrophilic model, and the measured frequency is 52 Hz, which is only 13.3% lower than the theoretical resultant frequency of 60 Hz. This additionally shows that the negative effect of the continuous impact on the superhydrophobic surface is significantly reduced compared with the hydrophilic model. Many derived droplets are generated, and these droplets are accelerated and detached under the action of vibration, which greatly reduces the contact time, and their contribution to the model mass is not as significant as it is for the hydrophilic model.