An empirical experimental investigation on the effect of an external electric field on the behaviour of laser-induced cavitation bubbles.

Abstract

This study is an attempt to empirically investigate the behaviour of laser-induced cavitation bubbles under the influence of an external electric field. As such two targets (copper and iridium) were subjected to a high-power Nd:YAG laser beam while being submerged in a liquid. Three different liquids were chosen for this purpose viz. acetone, ethanol, and distilled de-ionized water. The choice of the liquids was made with the underlying assumption that the conductivity of the liquids would play a significant role in responding to the applied external electric field and thus dictate the behaviour of the cavitation bubbles. A probe-beam method known as a beam deflection setup was employed for this experiment and the results were analyzed using the Rayleigh-Plesset model. The results revealed that the maximum radii of the cavitation bubbles increased in response to an increasing electric field. This effect was more pronounced in the presence of acetone medium and decreased successively while using ethanol and water media owing to their varying magnitudes of electrical conductivity. The bubble collapse speeds and their energies were also measured and similar trends were observed in both cases. The results from cavitation bubble dynamics were then applied to a Gilmore model and the sizes of the NPs synthesized using laser ablation with and without an external electric field were calculated using classical nucleation theory.