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| Effect of roughness on continuous directional transport of fluid in microchannel |
| CHEN Ya-jun1, LONG Wei1, YANG Shao-hua1, CHAI Hui1, JU Shao-hua2 |
1. College of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500, China;
2. State Key Laboratory Breeding Base of Complex Nonferrous Metal Resources Cleaning Utilization in Yunnan Province, Kunming 650093, China |
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Abstract The transport of samples in functional units of a microfluidic chip depends on the flow of the liquid in the microchannel. Scale effect aggravates the surface effect, which makes the flow in the microchannel possible to spread continuously without external power. In order to research flow mechanism and kinetic characteristics in microchannel intensively, influence factors of continuous directional transport in microchannel were analyzed based on the Derjaguin approximation, surface energy and Casimir effect, influences of surface roughness on flow characteristics and continuous directional transport efficiency in the microchannel were analyzed by both computational and experimental methods, and constitutive equations and flow control equations for fluids were defined. All above results were verified effective and credible. The results indicated that roughness of the inner wall was a very important factor affecting flow characteristics and continuous directional liquid transport efficiency in the microchannel. The variation of equivalent tooth number, tooth height or dip angle of tooth brought prominent change of main vortex and concomitant vortex in clearance flow near inner wall, which would cause the continuous directional transport efficiency of microfluidic change. The thesis provides some insights and references for the design operational management of microfluidic lubrication, friction reduction, anti-sticking, as well as miniaturization and integration in micro electro mechanical systems.
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Received: 12 June 2017
Published: 28 June 2018
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粗糙度对微流道内流体连续自搬运的影响
微流控芯片中各功能单元间样品的运输依赖于流体在微通道中的流动，尺度效应加剧表面作用效果，使得微流道内流体无需外部动力即可实现连续铺展搬运。为了深入研究微流道内流体的流动机制和动力学特性，分析影响微流道内流体自搬运效率的因素，基于近似Derjaguin法的同时充分考虑表面能和Casimir效应，利用数值计算和实验相结合的方法分析了微流道内壁粗糙度对流体流动特性和自搬运效率的影响，明确了微流道内流体的本构方程和流动控制方程，并设计搭建实验台验证所得结果的有效性和可靠性。结果表明：内壁粗糙度是影响微流道内流体流动特性和连续自搬运效率的重要因素；当粗糙度等效齿数、等效齿高和等效齿倾角变化时，微流道内近壁面齿隙间的主漩涡和伴生涡都相应改变，导致流体自搬运效率发生相应变化。研究结果对解决微流控润滑和微流控芯片减阻防粘等设计和使用问题具有重要理论指导意义，对微电子机械系统的小型化和集成化设计具有一定的参考价值。
关键词：
微流控芯片,
连续自搬运,
粗糙度,
Casimir效应,
表面能梯度
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