Laser-Induced Nanobubbles on Demand
* Presenting author
Abstract:
In this work we study the controlled nucleation of bulk nanobubbles in a liquid produced by the energy deposition of a high power laser pulse. The nucleation of the bubbles composing the cluster can not be seen even with a highly magnified optical arrangement. However, these transient bubbles became visible when expanded by a tensionwave passing through the light exposed region. The temporal delay between the bubble seeding and the rarefaction wave arrival could be precisely adjusted (e.g. 100 ns jitter). The clear correlation between illumination and cavitation nucleation observed in the experiments demonstrates that gaseous nanobubbles are indeed produced by the exposure of the liquid to the laser light, and not by acoustic cavitation or other processes. The radius of the gas cavities was characterized through high-speed microscopic imaging combined with numerical calculations on the bubble diffusion time based on the Epstein-Plesset theory. Different aqueous solutions with a wide variety of physical properties were tested in order to find suitable stabilization mechanisms for the nanobubbles. As the existence of stable bulk nanobubbles and their generation is still in debate, this laser-based nucleation technique could be a novel approach to provide relevant insight on the matter.