Nanobubbles on a very flat hydrophobic surface prepared by self-assembled monolayers

Takashi Nishiyama, Koji Takahashi, Yasuyuki Takata

Research output: Contribution to conferencePaperpeer-review

Abstract

Boiling is one of the most effective heat transfer methods due to its high heat transfer coefficient. Therefore, boiling heat transfer plays a very important role for various applications in many technological and industrial areas. However, a very complex mechanism of boiling, especially bubble nucleation, is still not sufficiently understood. On the other hand, numerous experiments have revealed the existence of soft domains that called nanobubbles at the solid-liquid interface. In this study, to investigate the influence of the solid-liquid interface nanobubbles on the bubble nucleation, an atomic force microscope (AFM) is used to characterize the morphology of nanobubbles. In order to separate the effect of wettability of a solid surface from that of surface structure, a very flat hydrophobic surface was prepared. 1H,1H,2H,2H-Perfluoro-noctylphosphonic acid (FOPA) formed the interface of hydrophobic self-assembled monolayers (SAMs). As the result of AFM measurement, many nanobubbles about 100 nm in diameter and 30 nm thick are observed at the interface of the FOPA surface and the pure water. In addition, to prove the existence of gaseous phase, the heat conductance measurement by time-domain thermoreflectance method (TDTR) was introduced. TDTR is an ultrafast optical pump probe technique well suited for thermal measurement of thin films. It enables to resolve the thermal conductivity of the thin film and the thermal conductance of the interface. If nanobubbles are the gaseous phase, the big change of interface heat thermal resistance will be seen and the TDTR signal should also change. The effectiveness of a TDTR to confirm the existence of nanobubbles is shown by the model simulation of TDTR. A clear difference is seen in TDTR signal by the existence of only 1 nm gaseous phase. After confirming the existence of nanobubbles by AFM measurement, it can be proved that the nanobubbles are truly gaseous phase of the TDTR measurement.

Original languageEnglish
DOIs
Publication statusPublished - Jan 1 2013
EventASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer, MNHMT 2013 - Hong Kong, China
Duration: Dec 11 2013Dec 14 2013

Other

OtherASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer, MNHMT 2013
CountryChina
CityHong Kong
Period12/11/1312/14/13

All Science Journal Classification (ASJC) codes

  • Fluid Flow and Transfer Processes

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