硅基底表面特性对微通道界面滑移的影响

发布时间：2018-03-17 01:11

本文选题：润湿性　切入点：超疏水　出处：《大连海事大学》2015年硕士论文　论文类型：学位论文

【摘要】：微流体系统作为微机电系统的一个重要分支,在生物医学、化学工程等领域具有广泛应用。随着微流体技术的发展,液体在微通道中流动的阻力特性成为研究的热点。微通道壁面的润湿性在很多情况下影响流体的流动,超疏水表面通过降低材料表面自由能,来减小微通道中固液之间的吸附作用,使得流体在壁面处发生速度滑移,从而减小界面阻力。本文从实验测试和数值模拟两个方面研究了表面润湿性对微通道中流体流动的影响。采用Micro-PIV微观粒子成像测速技术对由四种不同润湿特性的壁面两两组合的微通道进行流场测试,研究了壁面滑移速度与壁面润湿性之间的关系。结果表明,随着壁面疏水性的提高,壁面处的滑移速度增大；对于两侧壁面疏水性不同的微通道,最大速度位置偏向疏水性较强的一侧。在不同入口压力条件下,利用高速摄像系统记录空泡在由不同润湿性的硅表面组成的通道中的运动过程,研究了壁面润湿性对空泡在壁面处动态接触角的影响。研究发现,空泡动态接触角随着壁面疏水性的增强而增大,且一侧壁面疏水性的增强有助于提高另一侧壁面疏水性对动态接触角影响的敏感度。当入口压力小于40 kPa时,壁面润湿性对空泡动态接触角的影响占主导作用；入口压力大于等于40 kPa时,壁面润湿性作用减弱,压力成为主要影响因素。采用计算流体动力学对微通道的流场分布以及空泡运动形状进行了数值模拟,分析了空泡动态接触角、滑移速度以及壁面润湿性之间的关系。分析表明,流场速度决定了空泡头部的形状,且空泡在壁面处的动态接触角与滑移速度存在明确的对应关系,用动态接触角可以有效地表征壁面滑移。
[Abstract]:As an important branch of MEMS, microfluidic system is widely used in biomedicine, chemical engineering and so on. The resistance characteristics of liquid flowing in microchannels have become a hot topic. The wettability of microchannel wall affects the flow of fluid in many cases, and the superhydrophobic surface decreases the free energy of the material surface. To reduce the adsorption between solid and liquid in the microchannel, and make the fluid slip at the wall, In this paper, the effect of surface wettability on fluid flow in microchannels was studied from two aspects: experimental test and numerical simulation. The effects of Micro-PIV microparticle imaging velocimetry on the wetting properties of four different wetting properties were studied. The flow field of microchannels with pairwise combination on the wall is measured. The relationship between wall slip velocity and wall wettability is studied. The results show that the slip velocity increases with the increase of wall hydrophobicity, and for microchannels with different wall hydrophobicity, The maximum velocity position is in favor of the hydrophobic side. Under different inlet pressures, a high-speed camera system is used to record the motion of the cavitation in a channel composed of different wettable silicon surfaces. The effect of wall wettability on the dynamic contact angle of cavitation was studied. It was found that the dynamic contact angle of cavitation increased with the increase of hydrophobicity. The enhancement of hydrophobicity of one wall can improve the sensitivity of the hydrophobicity of the other side to the dynamic contact angle. When the inlet pressure is less than 40 kPa, the influence of wall wettability on the dynamic contact angle of cavitation is dominant. When the inlet pressure is greater than 40 kPa, the wettability of the wall becomes weaker, and the pressure becomes the main factor. The flow field distribution and the cavitation motion shape of the microchannel are numerically simulated by computational fluid dynamics (CFD). The dynamic contact angle, slip velocity and wall wettability of cavitation are analyzed. It is shown that the velocity of the flow field determines the shape of the cavitation head, and the dynamic contact angle of the cavitation at the wall has a clear relationship with the slip velocity. The wall slip can be effectively characterized by the dynamic contact angle.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH-39;TN304.12

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