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Study on Surface Tention Driving and Self-motion Behaviors of a Liquid Droplet

Author: ZhengDongMei
Tutor: LiuChangSong
School: Qingdao Technological University
Course: Mechanical Manufacturing and Automation
Keywords: Photoresponsive Gradient surface energy Self - assembled monolayers Self-motion Wettability
CLC: TB303
Type: Master's thesis
Year: 2010
Downloads: 61
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Abstract

In recent years, the the microfluidic drive control technology has caused more and more people's attention. The surface tension of the drive is an important way, the fluid-driven microfluidic devices depends on the wettability of the surface of controllability. In this paper, the optical response of self-assembled monolayers, according to vacuum ultraviolet prepared to make droplets spontaneous movement of the gradient surface energy surfaces, then studied different droplet movement in various gradient surface. Also reversible transition properties of zinc oxide film surface wettability. The study found that: (1) With the increase of the irradiation time, self-assembled monolayers etching effect gradually increased, resulting in the contact angle decreases, the surface can be gradually increased. With this feature, through heptadecafluorodecyl trimethoxy silane monomolecular film (FAS-SAM) for continuous illumination, prepared gradient surface energy surface. (2) The droplet in the gradient surface energy surface may be made of the low surface energy area to the high surface energy region of movement, its movement process can be divided into the acceleration phase and a deceleration phase. For the volume of 2μl of water droplets, and the contact angle on the surface of the surface energy in the gradient changes in the distance of 4.23mm for approximately 39 °, be reduced from 55.82 ° to 16.74 °, the maximum velocity of about 23.28mm / s. (3) proportional to the volume of the droplet velocity and droplet, is inversely proportional to the speed of movement of the baffle, i.e. the larger the droplet volume, paddle speed is smaller, faster droplet movement. In addition, the speed of movement of the water droplets on the surface of the horizontal gradient to be higher than the inclination gradient of the speed of movement on the surface, and the speed of movement of the droplets is greater than the speed of movement of the same volume of the droplet of formamide, and diethylene glycol in the same gradient surface. (4) to change the distance light also can be prepared by the gradient of the surface of the surface energy. The movement of the droplets on the motion of the surface of the kinds of gradient obtained with changing the illumination time of the gradient surface is similar. (5) by vacuum ultraviolet irradiation octadecyl trimethoxy silane monomolecular film (ODS-SAM) surface and the rough surface of the FAS-SAM may be formed gradient, but the droplets on these surfaces was not spontaneously movement. (6) of the zinc oxide thin film prepared on a glass substrate having a hydrophilic characteristic and is converted into a hydrophobic state, after the low-temperature heating; then through the high temperature heat treatment, will be converted into a hydrophilic state, i.e., the thin film having a hydrophobic / hydrophilic reversible transition properties. Moreover, the experiment proved that: the zinc oxide film surface the wettability transition critical temperature of 165 ° C. Controllable wettability of the zinc oxide thin film is expected to prepared the gradient of the surface of the surface energy.

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