In this thesis, we have studied water in contact with a hydrophobic surface. The thesisudcovers three interfacial phenomena which can occur in such a system: part I - sphericallyudcap-shaped gas bubbles (“surface nanobubbles”) residing on atomically smooth surfaces (10-100 nm). II - gas pockets, trapped in extremely small surface defects, growing to micrometer sized vapor bubbles (”cavitation”) (100-1000 nm); III - wetting dynamics of a rough, superhydrophobic surface (1-10µm). ududOur main result in part I is that the observed nanobubble shape does not depend on intrinsic cantilever properties, used in detecting the bubbles. Furthermore, we find that the nanoscopic contact angle (measured through the water) does not depend on the nanobubble radius and is much smaller (120 deg) than has hitherto been reported (~ 160 deg). Contamination is the most likely candidate to explain the latter observation.udIn part II, our main result is extremely little gas pockets (100nm) serve as nucleationudsites when the liquid pressure is lowered sufficiently and cavitation bubbles occur.udThe minimum pressure which is needed to nucleate the bubbles is inversely proportionaludto the pit radius and is in excellent agreement with the crevice model theory asuddeveloped in 1989. Hence, the origin of cavitation inception can be controlled andudunderstood down to submicroscopic dimensions.udWetting properties of superhydrophobic surfaces, which are useful in various applications, are studied in part III of the thesis.
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