Novel cavitation nuclei: Beyond particles and gas pockets*

Our understanding of the origin of bubble nucleation in water is still limited. The widely accepted model is the existence of gas pockets stabilized in a hydrophobic pore, which are present on impurities or in cracks on submerged surfaces. From these pockets cavitation bubbles might explosively expand once sufficiently strong tension is applied. Interestingly, in absence of well-controlled crevices, the measured cavitation threshold is much smaller than one would expect from the classical nucleation theory. This experimental fact was mostly argued that unresolved nanoscale gaseous nuclei stabilized by some means reduce the threshold of an otherwise pure liquid. Yet, these stabilized nanobubbles acting as cavitation nuclei have not been confirmed in experiments, neither on surfaces nor in the bulk.

Here, we demonstrate experimentally that atomically flat liquid-liquid interfaces can nucleate cavitation. These findings suggest that besides hydrophobic pores other mechanism of cavitation nuclei have to be accounted for in real liquids and their boundaries.

We induce a high-pressure region in a thin liquid gap via an optical breakdown from a focused pulsed laser. As a result, a transverse wave is launched in the gap that starts with a strong tension followed by a high pressure. Along the path of the rarefaction wave nuclei in the gap are expanded into microscopic visible cavitation bubbles, which are visualized with a high-speed camera.