Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, India.
Soft Matter. 2017 Oct 4;13(38):6858-6869. doi: 10.1039/c7sm00940b.
We report bio-inspired (from a hummingbird's tongue) liquid transport via elastocapillary interaction of a thin membrane with a liquid meniscus. A soft wedge-thin rectangular membrane forming a wedge with a rigid substrate and a flat thin rectangular membrane undergo large deformation while interacting with liquid menisci. The membrane deformation leads to the formation of confinement which in turn results in elastocapillary flow along the membrane length. A simple theoretical model based on the Euler Bernoulli law is used to predict the membrane deformation profiles, which compare well with that obtained from experiments. In the wedge case, the membrane surface and liquid are selected such that the Concus-Finn criterion is not satisfied to contrast the present case of elastocapillary flow from the typical corner flow reported in the literature. The meniscus location versus time studies indicated that the flow exhibits the typical Washburn regime with , except for a sudden increase in velocity at the end of the membrane length. The effects of membrane thickness and width, liquids and substrates were studied to determine the expression for the modified Washburn constant W in both the wedge and flat membranes. It was found that gravity plays a role for Bo > 0.94 and for Bo = 1.9, the effect of inclination angle on the flow was studied. The elastocapillary flow with thin membranes could open up an opportunity for a new area, namely "membrane microfluidics" or "lab on a membrane", for diagnostics and other applications.
我们报告了一种受蜂鸟舌头启发的液体传输方法，即通过薄膜与液体弯月面之间的弹毛细管相互作用来实现液体传输。一个软楔形薄矩形膜与刚性基底形成楔形，同时与液体弯月面相接触的薄矩形膜会发生大变形。膜的变形导致形成限制，从而导致沿着膜长度的弹毛细管流动。一个基于欧拉-伯努利定律的简单理论模型被用来预测膜的变形轮廓，这与实验结果吻合得很好。在楔形的情况下，选择膜表面和液体，使得Concus-Finn 准则不成立，这与文献中报道的典型角流的弹毛细管流动情况形成对比。弯月面位置随时间的研究表明，流动表现出典型的 Washburn 模式，除了在膜长度的末端速度突然增加。研究了膜的厚度和宽度、液体和基底的影响，以确定楔形和平面膜中修正 Washburn 常数 W 的表达式。结果表明，重力在 Bo > 0.94 和 Bo = 1.9 时起作用，研究了倾斜角度对流动的影响。薄膜的弹毛细管流动为诊断和其他应用开辟了一个新的领域，即“膜微流控”或“膜上实验室”。
