Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Langmuir. 2011 Sep 6;27(17):10360-4. doi: 10.1021/la202206p. Epub 2011 Jul 28.
Liquid dynamics in micropillar arrays have received significant fundamental interest and have offered opportunities for the development of advanced microfluidic, thermal management, and energy-harvesting devices. However, a comprehensive understanding of complex liquid behavior and the effect on macroscopic propagation rates in micropillar arrays is needed. In this work, we investigated the microscopic sweeping behavior of the liquid front along the spreading direction in micropillar arrays where the sweeping distance scales with the one-fifth power of time. We explain the scaling with a simplified model that captures the capillary pressure gradient at the liquid front. Furthermore, we show that such microscopic dynamics is the mechanism that decreases the macroscopic propagation rate. This effect is a result of the reduction in the interfacial energy difference used to generate the capillary pressure, which is explained with an energy-based model and corroborated with experiments. The results indicate the importance of accounting for the microscopic dynamics of the liquid on microstructured surfaces, particularly in sparse geometries.
微柱阵列中的液体动力学引起了人们的极大兴趣，为先进的微流控、热管理和能量收集装置的发展提供了机会。然而，需要全面了解复杂的液体行为以及其对微柱阵列中宏观传播速率的影响。在这项工作中，我们研究了在微柱阵列中液体前缘沿扩展方向的微观清扫行为，其中清扫距离与时间的五分之一次方成正比。我们用一个简化模型解释了这种标度关系，该模型捕获了液体前缘处的毛细压力梯度。此外，我们表明，这种微观动力学是降低宏观传播速率的机制。这种影响是由于用于产生毛细压力的界面能差减小所致，这可以用基于能量的模型来解释，并通过实验得到证实。结果表明，在微结构化表面上考虑液体的微观动力学的重要性，特别是在稀疏的几何形状中。
