la8b02887_si_002.pdf (356.18 kB)
Mechanical Stability of Surface Nanobubbles
journal contribution
posted on 2018-11-16, 00:00 authored by Duncan Dockar, Matthew K. Borg, Jason M. ReeseBubble 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.