We investigate the effects of surface stiffness on the air cushioning at the bottom of a liquid drop impacting onto a soft solid and the resulting entrapment of a central bubble. This was achieved using ultra-high-speed interferometry at 5 million frames per second and spatial resolution of 1.05 μm per pixel. The soft solid delays the effects of gas compressibility resulting in much larger air discs than corresponding impacts onto rigid surfaces. Using an effective impact velocity equal to half of the actual impact velocity brings the soft solid scaling behavior better in line with rigid substrate scaling. We also observe extended gliding of the drop as it initially avoids contact with the surface spreading over a thin layer of air and investigate the threshold velocity for the transition from gliding to ring contact. Such extended gliding layers have previously been seen for high-viscosity drop impacts, but not for low-viscosity liquids at the impact velocities used herein.

中文翻译：

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液滴撞击到柔软的固体上，会截留更多的空气。

我们研究了表面刚度对液滴底部的空气缓冲的影响，该空气缓冲撞击到软固体上，并导致夹带中央气泡。这是通过使用每秒500万帧的超高速干涉测量法和每个像素1.05μm的空间分辨率实现的。软固体延迟了气体可压缩性的影响，从而导致空气圆盘比对刚性表面的相应冲击大得多。使用等于实际冲击速度一半的有效冲击速度，可以使软固体结垢行为更好，与刚性基材结垢一致。我们还观察到液滴的延长滑动，因为它最初避免与散布在空气薄层上的表面接触，并研究了从滑动到环形接触过渡的阈值速度。