剪切率对微纳米间隙下流体边界滑移影响的试验研究

Experimental Research on Boundary Slip of Confined Liquids at Micro/nano Scale and Effect of Shear Rate

为了研究微纳米间隙下固液界面间流体的流动特性,采用修饰的原子力显微镜针尖,针对微纳米间隙下受限液体的边界滑移现象,对边界滑移在不同趋近速度下的特性进行了试验研究。固体壁面为Si(100)表面,试验液体为去离子水。试验结果表明,当球-盘间隙大于某一临界间隙后,不发生边界滑移;名义趋近速度越小,固液界面开始发生滑移的临界间隙越小,表现出明显的速度相关性。为进一步探究滑移和运动速度相关的原因,研究了固液界面上流体剪切率的分布规律,研究结果证实,边界滑移与剪切率相关,但只有在达到某一极限剪切率时才会发生边界滑移。

In order to research the flow property of liquids between solid and liquid at micro/nano scale, a commercial atomic force microscope was modified by attaching a glass ball to the end of cantilever at micro/nano scale, which was used to investigate influence of approach velocity on boundary slip. Solid surface specimen was Si（100）verse deionized water. Results indicate that, when the distance between the glass ball and solid surface is below critical value, boundary slip will not affect the hydrodynamic force. The critical distance will decrease with the reducing of the velocity and it means boundary slip is dependent with velocity. The relationship between shear rate and boundary slip was discussed. It shows that boundary slip will occur only when the shear rate reaches some value.