When a droplet impacts a (super-)hydrophobic surface, there is a range of Weber numbers within which bubble entrapment will occur during droplet recoil due to closure of the air cavity developed when the droplet spreads out during the impact. In this study, we studied bubble entrapment using a microelectromechanical system (MEMS)-based acoustic sensor fabricated on a substrate. We found that bubble entrapment is followed by an acoustic vibration that can be detected by the sensor. Moreover, the frequency of the vibration is inversely proportional to the radius of the droplet, which indicates that this vibration is the resonant oscillation of the bubble. Therefore, the MEMS-based acoustic sensor can be used not only to detect but also to measure the size of the entrapped bubble. Finally, we demonstrated that it is possible to prevent bubble formation by allowing the air to escape to the underside of the droplet contact area. This can be done by creating through-holes on the substrate or decorating the substrate with sufficiently large textures.

当液滴撞击（超）疏水表面时，存在一定范围的韦伯数，在该范围内，由于液滴在撞击过程中散开时形成的气腔闭合，在液滴反冲期间会发生气泡截留。在这项研究中，我们使用在基板上制造的基于微机电系统 (MEMS) 的声学传感器研究了气泡截留。我们发现，气泡夹带之后会发生声学振动，传感器可以检测到这种振动。而且，振动的频率与液滴的半径成反比，这表明这种振动是气泡的共振振荡。因此，基于 MEMS 的声学传感器不仅可用于检测，还可用于测量夹带气泡的大小。最后，我们证明了通过让空气逸出到液滴接触区域的下侧来防止气泡形成是可能的。这可以通过在基板上创建通孔或用足够大的纹理装饰基板来完成。