Evaporating characteristics of sessile droplet on hydrophobic and hydrophilic surfaces

초록

This study investigates evaporation characteristics of water droplets on hydrophobic and hydrophilic surfaces experimentally. The time-dependent contact angle, center-height, contact radius, surface area, and volume of droplet were measured for slide glass, octadecyltricholorosilane (OTS), and alkylketene dimmer (AKD) surfaces using the digital image analysis technique. First, during the evaporation of droplet on hydrophilic surface, the measured contact angle, liquid volume, and height of droplet were in good agreements with numerical predictions. It was found that there are no three distinct stages and no pinning section during the evaporation for the super-hydrophobic surface, and the surface characteristics highly affect evaporation speed rather than the droplet surface area contact with air. Moreover, as the hydrophobicity of surfaces becomes strong, the pinning time becomes short and the total evaporation time lasts long. In particular, the edge shrinking velocity of the droplet shows nonlinear characteristics, and its magnitude becomes extremely high at the last period of total evaporating time. (C) 2009 Elsevier B.V. All rights reserved.

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