la8b02887_si_002.pdf (356.18 kB)

Mechanical Stability of Surface Nanobubbles

Download (356.18 kB)
journal contribution
posted on 16.11.2018 by Duncan Dockar, Matthew K. Borg, Jason M. Reese
Bubble cavitation is important in technologies such as noninvasive cancer treatment and diagnosis, surface cleaning, and waste-water treatment. The cavitation threshold is the critical external tensile pressure that induces unstable growth of the bubble. Surface nanobubbles have been previously shown experimentally to be stable down to −6 MPa, in disagreement with the Blake threshold, which is the classical cavitation model that predicts bulk bubbles with radii ∼100 nm should be unstable below −0.6 MPa. Here, we use molecular dynamics to simulate quasi-two-dimensional (2D) and three-dimensional (3D) nitrogen surface nanobubbles immersed in water, subject to a range of pressure drops until unstable growth is observed. We propose and assess new cavitation threshold models, derived from mechanical equilibrium analyses for both the quasi-2D and 3D cavitating bubbles. The discrepancies from the Blake threshold are attributed to the pinned contact line, within which the surface nanobubbles grow with constant lateral contact diameter, and consequently a reduced radius of curvature. We conclude with a critical discussion of previous experimental results on the cavitation of relatively large surface nanobubbles.