Interfacial phenomena in micro- and nanofluidics: nanobubbles, cavitation, and wetting

Bram Matthias Borkent

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

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Abstract

In this thesis, we have studied water in contact with a hydrophobic surface. The thesis covers three interfacial phenomena which can occur in such a system: part I - spherically cap-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). Our 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. In part II, our main result is extremely little gas pockets (100nm) serve as nucleation sites when the liquid pressure is lowered sufficiently and cavitation bubbles occur. The minimum pressure which is needed to nucleate the bubbles is inversely proportional to the pit radius and is in excellent agreement with the crevice model theory as developed in 1989. Hence, the origin of cavitation inception can be controlled and understood down to submicroscopic dimensions. Wetting properties of superhydrophobic surfaces, which are useful in various applications, are studied in part III of the thesis.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Lohse, Detlef , Supervisor
Award date2 Oct 2009
Place of PublicationEnschede
Publisher
Print ISBNs978-90-365-2870-2
DOIs
Publication statusPublished - 2 Oct 2009

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cavitation flow
wetting
bubbles
gas pockets
theses
radii
surface defects
water
micrometers
contamination
cracks
vapors
liquids
gases

Keywords

  • IR-68408

Cite this

Borkent, Bram Matthias. / Interfacial phenomena in micro- and nanofluidics : nanobubbles, cavitation, and wetting. Enschede : University of Twente, 2009. 189 p.
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abstract = "In this thesis, we have studied water in contact with a hydrophobic surface. The thesis covers three interfacial phenomena which can occur in such a system: part I - spherically cap-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). Our 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. In part II, our main result is extremely little gas pockets (100nm) serve as nucleation sites when the liquid pressure is lowered sufficiently and cavitation bubbles occur. The minimum pressure which is needed to nucleate the bubbles is inversely proportional to the pit radius and is in excellent agreement with the crevice model theory as developed in 1989. Hence, the origin of cavitation inception can be controlled and understood down to submicroscopic dimensions. Wetting properties of superhydrophobic surfaces, which are useful in various applications, are studied in part III of the thesis.",
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Interfacial phenomena in micro- and nanofluidics : nanobubbles, cavitation, and wetting. / Borkent, Bram Matthias.

Enschede : University of Twente, 2009. 189 p.

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

TY - THES

T1 - Interfacial phenomena in micro- and nanofluidics

T2 - nanobubbles, cavitation, and wetting

AU - Borkent, Bram Matthias

PY - 2009/10/2

Y1 - 2009/10/2

N2 - In this thesis, we have studied water in contact with a hydrophobic surface. The thesis covers three interfacial phenomena which can occur in such a system: part I - spherically cap-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). Our 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. In part II, our main result is extremely little gas pockets (100nm) serve as nucleation sites when the liquid pressure is lowered sufficiently and cavitation bubbles occur. The minimum pressure which is needed to nucleate the bubbles is inversely proportional to the pit radius and is in excellent agreement with the crevice model theory as developed in 1989. Hence, the origin of cavitation inception can be controlled and understood down to submicroscopic dimensions. Wetting properties of superhydrophobic surfaces, which are useful in various applications, are studied in part III of the thesis.

AB - In this thesis, we have studied water in contact with a hydrophobic surface. The thesis covers three interfacial phenomena which can occur in such a system: part I - spherically cap-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). Our 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. In part II, our main result is extremely little gas pockets (100nm) serve as nucleation sites when the liquid pressure is lowered sufficiently and cavitation bubbles occur. The minimum pressure which is needed to nucleate the bubbles is inversely proportional to the pit radius and is in excellent agreement with the crevice model theory as developed in 1989. Hence, the origin of cavitation inception can be controlled and understood down to submicroscopic dimensions. Wetting properties of superhydrophobic surfaces, which are useful in various applications, are studied in part III of the thesis.

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CY - Enschede

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