Summary: Atomic Force Microscope Images of Nanobubbles on a
Hydrophobic Surface and Corresponding
J. W. G. Tyrrell and P. Attard*
Ian Wark Research Institute, University of South Australia,
Mawson Lakes, SA 5095, Australia
Received July 30, 2001. In Final Form: October 17, 2001
Domains, apparently nanobubbles, have been observed on a hydrophobic glass surface in water using
an atomic force microscope operated in tapping mode. Phase images show the domains to be softer than
the underlying substrate. Complementary force curves between a silica colloid probe and the glass surface
to the height of the imaged domains. Images and force curves have been acquired over a range of pH
conditions to probe the nature of the overall interaction and gain some insight into the conformation of
nanobubbles on the sample surface. The bubbles appear to regrow following their removal by the application
of high loads through either contact mode imaging or tapping mode imaging at high drive amplitudes. They
are not present in a solvaphilic fluid (ethanol) but regrow following the subsequent reintroduction of H2O.
The correlation between image and force data, supported by existing results in the literature, provides
strong evidence to favor nanobubbles as the origin of the hydrophobic force.