Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM-The role of nanoscopic bubbles in the interactions

Naoyuki Ishida, Ko Higashitani

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48 Citations (Scopus)


The interaction forces between a hydrophobic silicon plate and a silica particle in an aqueous solution were investigated with an atomic force microscope (AFM). The surfaces were hydrophobized chemically by a silane coupling agent, and the hydrophobicity (contact angle θ) of the surfaces was varied. The interactions were long-ranged at θ > 90° with a discontinuous step appearing in the approaching and separating force curves respectively. The range and magnitude of the interaction were decreased with decreasing θ. On the other hand, the interactions at θ = 80° was unstable and no long-range attraction was observed. When the gas phase on the surfaces was removed by flushing organic solvents between the surfaces, the interactions became short-ranged at θ > 90°, and the interaction was described DLVO theory at large distances at θ = 80°. A large number of nano-size domain structures were found on the surfaces by tapping-mode AFM. These results imply that the bridging of nanobubbles is the main origin of the long-range force between chemically hydrophobized surfaces and that the size of the bubble has critical effect on the range and magnitude of the attractive force. The short-range interactions without bubbles were found to consist of an electrostatic repulsive force at larger distances and an attractive force, which was sufficiently longer-ranged than the van der Waals force, at smaller distance.

Original languageEnglish
Pages (from-to)719-725
Number of pages7
JournalMinerals Engineering
Issue number6-8
Publication statusPublished - May 2006
Externally publishedYes


  • Fine particle processing
  • Flotation kinetics
  • Surface modification

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Chemistry(all)
  • Geotechnical Engineering and Engineering Geology
  • Mechanical Engineering


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