微纳尺度下固液界面流体阻力多因素耦合影响机理及规律的研究

Micro/Nanofluidic systems, which are developed based on the micro/ nano technology, obtained remarkable achievements in mechanical, biological, chemical and biomedical applications. The control of the drag of fluid flow in micro/ nano scale is one of the key factors for the development of Micro/nanofluidic systems. The study of the formation mechanism and influence factors of the drag of fluid flow has important theoretical and practical value. This research firstly studies the effect of nanobubbles on the boundary slip at the interface of solid and liquid based on theoretical analysis and experimental methods, and obtains the effect of nanobubbles on the drag of liquid flow. Secondly, the co-influence of surface charge, electroviscosity, boundary slip and nanobubbles are investigated based on the solid, liquid, gas coupling theory, and one-dimensional and two-dimensional mathematical models of the velocity field within the micro/ nano scale channels are established to obtain the co-effects on the drag of fluid flow in micro/ nano scale. Then the characteristic parameters of nanobubbles, surface charge density and slip length are measured using an modified AFM which can applies electric filed to the experimental system, at the meantime, the flow rate of micro/nano pipeline flow is measured by using micro-flowmeter to verify the theoretical analysis. Finally a method which can control the drag of fluid flow in micro/nanofluidic system by changing the surface charge density is explored.

基于微纳米技术的微纳流体系统的发展，使其在机械、生物、化学、医学以及生物医学等领域取得了引人瞩目的业绩。目前微纳米尺度下的流体阻力的控制已成为制约微纳流体系统发展的关键因素之一，对流体阻力的形成机理和影响因素的研究具有重要的理论意义和实用价值。本课题首先利用理论分析和实验相结合的方法研究固液界面上纳米气泡影响边界滑移的机理，得到纳米气泡对液体流动阻力的影响规律；然后以固液气三态耦合理论为基础，分析表面电荷、电粘度效应、边界滑移和纳米气泡之间耦合作用机理，建立一、二维微纳通道内的流速场数学模型，得到微纳尺度下固液界面流体阻力多因素耦合影响机理及规律。利用改造后具有外加电场功能的AFM测量固液界面纳米气泡特征参数、表面电荷密度、边界滑移长度，同时利用微流量计测量微纳管道流量流速，验证理论分析结果的正确性。最后探索一种基于改变表面电荷密度实现控制微纳流体系统内流动阻力的方法。

本课题的主要研究内容包括：表面电荷、电粘度效应、边界滑移和纳米气泡对流体阻力耦合影响的研究；微通道液体流动流速场理论模型的建立，并分析减小其流体阻力的途径和基于改变表面电荷密度实现控制微纳流体系统内流动阻力的研究。主要研究内容与计划相符。取得的主要成果如下：实验得到了表面电荷对边界滑移的影响规律，首次观察到了纳米气泡分布参数的变化导致的边界滑移长度的变化，证实了纳米气泡对边界滑移具有较为显著的影响。通过综合分析表面电荷对纳米气泡、边界滑移的影响规律以及纳米气泡对边界滑移的影响规律，得到了表面电荷、边界滑移、纳米气泡对液体流动阻力的耦合影响规律，对分析微纳尺度下液体的流动具有重要的理论意义。建立了为微通道内液体流动流速场的理论模型，分析了表面电荷、边界滑移对微通道内液体流动的耦合影响，对微纳流体系统的设计具有较高的参考价值。通过改变表面电荷，实现了液体在微纳尺度下流动阻力的变化，验证了所建立的理论模型的有效性，基本完成了项目计划书中的研究目标。此外，还在项目的支持下，通过分析固液界面上固体表面与液体之间关系，构建了超疏油、超亲水复合结构涂层，实现了高效油水分离，具有重要的应用前景。