表面润湿性对微通道界面减阻特性的影响

目的降低微通道的流动阻力。方法借助激光加工、自组装技术和化学涂覆技术,在Si基底上制备了3种不同润湿性的表面,通过组装获得具有不同润湿性壁面的微通道。采用微观粒子成像测速技术(μ-PIV),对构建的微通道单侧滑移流动和双侧滑移流动进行测试。结果 Si表面沉积自组装分子膜、微结构加工结合自组装分子膜沉积及构筑微结构后,进行纳米二氧化硅涂覆的接触角分别为114.6°、142.7°和155.4°。亲水壁面A与疏水壁面B、C和超疏水壁面D组成的微通道,B、C和D壁面的滑移速度分别为0.018、0.022、0.029 m/s。B-D通道的平均流速比B-C通道提高了0.85%,C-D通道的平均流速比C-C通道提高了5.25%。结论疏水壁面处均存在较明显的滑移速度,且壁面疏水性越强,滑移速度越大。当两侧壁面均为疏水壁面时,一侧壁面疏水性的提高可以增加另一侧壁面疏水性对整体减阻效果的影响,但会迫使另一侧疏水壁面的滑移速度减小。流场中最大速度位置会偏向疏水性较强的一侧壁面,且两侧壁面润湿性的差距越大,其偏离距离越大。

Effects of Surface Wettability on Interfacial Drag Reduction in Micro-channel

To reduce the flow drag in micro channel, by the technology of laser manufacturing, self-assembled monolay-er(SAM) technique and chemical coating, three kinds of surfaces with different wettabilities were obtained. Then the mi-cro-channels whose wall surfaces were constituted by theses surfaces, were manufactured. The flow fields of these mi-cro-channels were tested by the microscopic particle image velocimetry (μ-PIV), including the single wall's slip experiment and the double walls' slip experiment. The contact angles were 114.6°, 142.7°, 155.4° after SAM deposition, microstructure manu-facturing(MM) and SAM deposition, MM and chemical coating on silicon wafer, respectively. The slip velocities were 0.018, 0.022, 0.029 m/s on hydrophobic specimen B、C and superhydrophobic specimen D wall surface when they were combined the micro-channel with A specimen. The average flow velocity in B-D micro-channel increase 0.85% than that of in B-C micro-channel. The averasge flow velocity in C-D micro-channel increase 5.25% than that of in C-C micro-channel.There are obvious slip velocities near the hydrophobic surfaces, and the slip velocity increases with the enhance of the wall's hydropho-bicity. When the two walls of channel are both hydrophobic, the slip velocity of the other wall will decrease with the increase of one wall's hydrophobicity, but the effect of the other wall's hydrophobicity on drag reduction will improve. The position of the maximum velocity locates on the region which is closer to the wall with stronger hydrophobicity, instead of the center part of channel. Moreover, the bigger the difference between the two wall's wettability, the greater the deviation.