2013 Fiscal Year Final Research Report

Investigation of the dew condensation and subsequent spontaneous jumping of droplets on the highly hydrophobic surface under cooling

Research Project

Project/Area Number	24655117
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Single-year Grants
Research Field	Functional materials chemistry
Research Institution	Tokyo Institute of Technology
Principal Investigator	NAKAJIMA Akira 東京工業大学, 理工学研究科, 教授 (00302795)
Project Period (FY)	2012-04-01 – 2014-03-31
Keywords	撥水 / 結露 / 凝結 / 濡れ / 跳躍
Research Abstract	Superhydrophobic coatings with nano-scale random roughness structure were prepared using boehmite and hydrophobic silanes. The samples were cooled by Peltier cooling element, and spontaneous jumping of water droplets formed on the coatings by dew condensation was observed from two different directions using high-speed camera systems. Spontaneous jumping of water droplets occurred subsequent to coalescence of more than two water droplets, deformation, and shape recovery. Small jumping droplets exhibited great initial jumping velocity. Initial jumping velocity decreased with increasing the difference in droplet sizes before coalescence. Actual jumping velocity was smaller than the theoretical value. When the sample was declined at 30 degrees, jumping frequency of water droplets repeated the increasing-decreasing cycle against cooling time and sustained droplet removal property. The jumping height of water droplets was remarkably increased under an external electric field.

(4 results)