We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst of focused ultrasound. Alignment of the ultrasound focus and the pressure amplitudes in the vicinity of the cavity dictate the direction and length of the resulting jet, respectively. We interpret our observations in terms of radiation forces exerted on the cavity, due to the pressure gradient introduced to the ultrasound focus by its presence. We support our hypothesis with a linear analysis of the force distribution across the cavity surface, at the moment of maximum inflation, which shows reasonable predictive agreement with the observed jet characteristics.
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We are grateful to Prof John Blake and his group for continuing and constructive discussions regarding our observations. The authors acknowledge the EPSRC loan pool, particularly A. Walker, for the loan of the high speed camera. This work was supported by EU FP7 IAPP Grant No. 230674 (Nanoporation Project) and a UK EPSRC grant, “Sonotweezers.” B.G. is also supported by a UK EPSRC DTA award. D.M. thanks the Royal Society for support. P.P. acknowledges the Norwegian Research Council for an Yggdrasil mobility award.