Dynamics of a disturbed sessile drop measured by atomic force microscopy (AFM)

Patricia M. McGuiggan, Daniel A. Grave, Jay S. Wallace, Shengfeng Cheng, Andrea Prosperetti, Mark O. Robbins

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (<100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

Original languageEnglish
Pages (from-to)11966-11972
Number of pages7
JournalLangmuir
Volume27
Issue number19
DOIs
StatePublished - 4 Oct 2011
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science (all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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