Modeling the Physics of Bubble Nucleation in Histotripsy

Study on a novel omnidirectional ultrasonic cavitation removal system for Microcystis aeruginosa

“…The thermal motions within the liquid form temporary and microscopic voids that can constitute the nuclei necessary for the rupture and growth of macroscopic bubbles [35] . Meanwhile, the liquid enters a metastable state when it is stretched beyond its vapor pressure or superheated above the boiling point, at which time the thermal deposition in the liquid facilitates bubble nucleation by lowering the cavitation threshold [36] , [37] .…”

Mechanisms of nuclei growth in ultrasound bubble nucleation

“…This model suggested that at room or physiological temperatures, the acoustic pressure significantly affects the rate at which bubbles nucleate. Conversely, nucleation rates increase up to 20 orders of magnitude between 60 and 100 °C, where the liquid's temperature is the driving parameter of the process [2] , due to an increasing vapour pressure and a decreasing surface tension at high temperatures.…”

“…The theory derived in [1] , [2] is a thermodynamic theory, which considers vapour transport as the sole mechanism involved in nuclei growth. Although that model can predict spatial–temporal trends of bubble nucleation within focused acoustic fields, it is skewed towards highlighting the energetic requirements of nucleation via the surface tension term in detriment of the effects of bubble radial dynamics.…”

“…There are two broad categories of histotripsy which relate to the mechanism driving bubble nucleation. On the one hand, boiling histotripsy [15] , [16] takes place at high temperatures in the presence of acoustic shockwaves of about −16 MPa peak negative pressure [1] , [2] . On the other hand, cavitation histotripsy, usually classified as cavitation cloud [17] , shock-scattering [18] or intrinsic threshold [7] histotripsy, occurs at physiological temperatures with peak-negative focal pressures around −30 MPa within as little as two ultrasound cycles.…”

“…Alternatively, boiling bubble nucleation usually happens following millisecond non-linear heat deposition due to the absorption of shockwaves [27] . The ultrasound focal volume transforms mechanical energy into heat until the temperature-dependent nucleation threshold equals the peak-negative ultrasound pressure at the focus, causing the appearance of a boiling bubble [2] . Numerical studies of boiling bubbles show that they can grow from nano to millimetre sizes by vapour and gas transport across their surface [9] , [28] , [29] .…”