Bubbles to penetrate cell membranes

Fluid dynamics concerning bubbles are complex and interesting. When a bubble collapses, flow jet might be created at high speed. When it hits on something, the force can be quite large. Here is a delicate experiment that explores this phenomenon to practical ends [Phys. Rev. Lett. 105, 078101 (2010)].

Figure caption: The timed expansion and collapse of two bubbles creates a liquid jet that can penetrate a fine hole in the membrane of a cell. From left to right: A laser (green circle) focused inside a water bath locally vaporizes the liquid, creating an expanding bubble (light blue). Just after the first bubble reaches its maximum size, a second laser (red circle) generates another bubble. As the second bubble expands and the first bubble collapses, a rush of liquid forms along the vertical line (pink arrow) between the two, creating a high-speed liquid jet that accelerates toward the cell with enough force to penetrate the membrane.