Wettability of AFM tip influences the profile of interfacial nanobubbles

Hideaki Teshima, Koji Takahashi, Yasuyuki Takata, Takashi Nishiyama

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

To accurately characterize the shape of interfacial nanobubbles using atomic force microscopy (AFM), we investigated the effect of wettability of the AFM tip while operating in the peak force tapping (PFT) mode. The AFM tips were made hydrophobic and hydrophilic by Teflon AF coating and oxygen plasma treatment, respectively. It was found that the measured base radius of nanobubbles differed between AFM height images and adhesion images, and that this difference depended on the tip wettability. The force curves obtained during the measurements were also different depending on the wettability, especially in the range of the tip/nanobubble interaction and in the magnitude of the maximum attractive force in the retraction period. The difference suggests that hydrophobic tips penetrate the gas/liquid interface of the nanobubbles, with the three phase contact line being pinned on the tip surface; hydrophilic tips on the other hand do not penetrate the interface. We then quantitatively estimated the pinning position and recalculated the true profiles of the nanobubbles by comparing the height images and adhesion images. As the AFM tip was made more hydrophilic, the penetration depth decreased and eventually approached zero. This result suggests that the PFT measurement using a hydrophilic tip is vital for the acquisition of reliable nanobubble profiles.

Original languageEnglish
Article number054303
JournalJournal of Applied Physics
Volume123
Issue number5
DOIs
Publication statusPublished - Feb 7 2018

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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