Professor Atsuki Komiya

Institute of Fluid Science

Tohoku University

komiya@tohoku.ac.jp

Professor Atsuki Komiya is head of Heat Transfer Control Laboratory in the Institute of Fluid Science, Tohoku University, Japan. He received the PhD in mechanical engineering in Tohoku University in 2002. From 2002 to 2004, he was a Research Fellow with the Japan Aerospace Exploration Agency (JAXA). He worked the development of the facility of fluid experiment for space experiment. In 2004, he moved to the Tohoku University as an Assistant Professor. Since 2019, he has been a Professor of Tohoku University. He is the author of two books, more than 140 refereed papers and more than 2000 citations. Professor Komiya’s awards and honors include the Young Researcher Award and Scientific Contribution Award of the Heat Transfer Society of Japan, and the Young Scientists’ Prize of the Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology.

Title: Edge formation of small droplet on a substrate – Nano-scale visualization of precursor film dynamics –

Abstract: Phase-shifting ellipsometer, which can precisely visualize two-dimensional thin film thickness at the edge of small droplet has been developed in our laboratory. Experimental investigation in the vicinity of boundary area of three phases, solid-liquid-gas interface namely “contact line” is important for understanding of the phase change phenomena, such as boiling, condensation, and surface events such as wetting and drying phenomena. Theoretically, de Gennes has proposed a formula for a thickness of precursor film under the assumption that the wetting process obeys a viscous flow driven by disjoining pressure. This theoretical approach shows a formation of precursor film, however it is difficult to achieve precise measurement of nanoscale thickness of the film. In this study, we have developed a visualization system for the measurement of two-dimensional thickness distribution of the precursor film by using a phase-shifting technique. The proposed system could measure the transient thickness distribution. At the initial stage of droplet formation, the thickness of the edge region got thicker compared with that of inner region. However, its thickness difference decreases with the droplet spreading. From the visualization results of two-dimensional image, the relation between circumferential shape of precursor film and surrounding condition was also discussed.