Tuning bubbly structures in microchannels.
Tuning bubbly structures in microchannels.
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DOI：
10.1063/1.3693605
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发表时间：
2012-04
期刊：
影响因子：
3.2
通讯作者：
Sharon M. Vuong;S. Anna
中科院分区：
文献类型：
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作者：
Sharon M. Vuong;S. Anna
泡沫具有许多有用的应用，这些应用源于泡沫中气泡的结构和尺寸分布。微流体允许快速形成均匀的气泡，其中气泡尺寸和体积分数是输入气体压力、液体流速和装置几何形状的函数。在形成之后，微通道限制气泡并决定所得泡沫结构。气泡结构可以从单行（“滴落”）到多行（“交替”），再到密集堆积的气泡（“竹子”和干泡沫）。我们发现，每种配置出现在由气泡体积和体积分数定义的操作空间的不同区域。我们描述了这些区域之间的边界，使用几何参数，并表明，边界的通道纵横比的函数。我们比较这些几何参数与泡沫结构中观察到的实验中使用流动聚焦，T-接头，并协同流设计，以产生稳定的氮气泡在表面活性剂水溶液和稳定的液滴在油中含有溶解的表面活性剂。这项工作的结果是一组设计参数，可用于实现所需的泡沫结构作为设备的几何形状和实验控制参数的函数。
Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row ("dripping"), to multiple rows ("alternating"), to densely packed bubbles ("bamboo" and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters.