Focusing of liquid jets induced by the collapse of gas bubbles at a liquid-air interface.*

In this work the focusing of jets induced by the collapse of gas bubbles at a liquid-air interface is presented.

The liquid is confined between two glass slides (h ≈ 50 um, determined by spacers). Gas bubbles are formed by trapping air during the expansion and collapse of a laser-induced bubble (Rmax ≈ 40 um) very close to the interface (d ≤ 60 um). This process can be repeated at different positions to generate several bubbles at the interface. The collapse of the gas bubbles is induced by the generation of a cavitation bubble (Rmax ≈ 500 um) at controlled distances from the interface ( d ≈ 750 um).

Using high-speed video, we study the dynamics of the induced jets. We show that the individual dynamics of each jet is modified as function of the number of bubbles at the interface as well as the separation between them, determining the conditions for focusing the liquid jets.