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Shocking bubbles - acoustic cavitation and its non-linear emissions

Bubble activity in liquids subject to ultrasonic driving – acoustic cavitation – is a rapid, energetic, and highly non-linear phenomenon, that remains not fully understood. Despite this, cavitation is utilised (or under investigation for utilisation) in a surprising variety of applications, some relatively well known and established such as acoustic cleaning, or contrast enhancement during medical ultrasound imaging, with more recent applications including drug delivery to the brain, and sono-exfoliation of graphite for graphene production.

In this talk, I will review predominantly experimental work based on high-speed imaging and acoustic detection, undertaken at the Cavitation Laboratory (CavLab), seeking to understand the cavitation acoustic emission signal in term of source bubble dynamics. This has particular relevance to medical therapy applications, where non-linear components generated by cavitating microbubbles or other nucleation particles, are used to ensure safety and efficacy of cavitation activity, in-vivo.

Time permitting, I will also review results from a number of other ultrasonic sources/systems that we have investigated, including a sonotrode (ultrasonic horn) and a cleaning bath. This overview suggests that – at least in terms of the emission signal generated – an acoustic bubble is just an acoustic bubble, doing what acoustic bubbles do…