Microscopic origin of the humidity dependence of the adhesion force in atomic force microscopy

Joonkyung Jang, Mino Yang, George Schatz

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Water condenses between an atomic force microscope (AFM) tip and a surface to form a nanoscale bridge that produces a significant adhesion force on the tip. As humidity increases, the water bridge always becomes wider but the adhesion force sometimes decreases. The authors show that the humidity dependence of the adhesion force is intimately related to the structural properties of the underlying water bridge. A wide bridge whose width does not vary much with tip-surface distance can increase its volume as distance is increased. In this case, the adhesion force decreases as humidity rises. Narrow bridges whose width decreases rapidly with increasing tip-surface distance give the opposite result. This connection between humidity dependence of the adhesion force and the structural susceptibility of the water bridge is illustrated by performing Monte Carlo simulations for AFM tips with various hydrophilicities.

Original languageEnglish
Article number174705
JournalJournal of Chemical Physics
Issue number17
Publication statusPublished - May 14 2007


ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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