Department of Chemical and Materials Engineering , University of Alberta , 12-211 Donadeo Innovation Centre for Engineering , Edmonton , Alberta , Canada T6G1H9.
Langmuir. 2018 Sep 11;34(36):10659-10667. doi: 10.1021/acs.langmuir.8b02173. Epub 2018 Aug 23.
The formation and evolution of immersed surface micro- and nanobubbles are essential in various practical applications, such as the usage of superhydrophobic materials, drug delivery, and mineral flotation. In this work, we investigate the entrapment of microbubbles on a hydrophobic surface, structured with microwells, when water flow passes along, and the subsequent microbubble dissolution. At entrapment, the microbubble is initially pinned at the edge of the microwell. At some point, the three-phase contact line detaches from one side of the edge and separates from the wall, after which it further recedes. We systematically investigate the evolution of the footprint diameter and the contact angle of the entrapped microbubbles, which reveals that the dissolution process is in the constant contact angle mode. By varying the gas undersaturation level, we quantify how a high gas undersaturation enhances the dissolution process, and compare with simplified theoretical predictions for dissolving bubbles on a plane surface. We find that geometric partial blockage effects of the diffusive flux out of the microbubble trapped in the microwell lead to reduced dissolution rates.
浸入式表面微纳气泡的形成和演化在各种实际应用中至关重要，例如超疏水材料的使用、药物输送和矿物浮选。在这项工作中，我们研究了当水流沿微槽结构的疏水表面流动时微气泡的捕获以及随后的微气泡溶解。在捕获过程中，微气泡最初被固定在微槽的边缘。在某一时刻，三相接触线从边缘的一侧脱离并与壁分离，然后进一步后退。我们系统地研究了捕获的微气泡的足迹直径和接触角的演化，这表明溶解过程处于恒定接触角模式。通过改变气体过饱和度水平，我们量化了高气体过饱和度如何增强溶解过程，并与平面上溶解气泡的简化理论预测进行了比较。我们发现，被困在微槽中的微气泡中扩散通量的几何部分阻塞效应导致溶解速率降低。
