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Droplet Pattern Formation and Translation in New Microfluidic Flow-Focusing Devices
Hua-guo Xu,Hao-jun Liang*
Author NameAffiliationE-mail
Hua-guo Xu CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China  
Hao-jun Liang* Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Tech-nology of China, Hefei 230026, China hjliang@ustc.edu.cn 
Abstract:
We conducted experiments on specially designed microfluidic chips that generate droplets through a microfluidic ow-focusing approach. The fluid flow in the microfluidic channel produced a shear flow field at low Reynolds numbers. The droplets in the microfluidic system exhibited special droplet pattern formations similar to periodic crystal-like lattices because of the competition between shear forces and surface tension. By adjusting the flow rate ratio of the water (droplet phase) to oil (continuous phase) phases and changing the outlet channel widths, the droplets formed monolayer dispersion to double-layer formation to monolayer squeezing when the outlet channel widths were 250 or 300 μm. We also obtained droplets with monolayer dispersion, three-layer arrangements, double-layer squeezing, and monolayer squeezing when the outlet channel width was 350 μm. The outlet channel width was increased to 400 μm, and four-layer arrangements were observed. We also studied the translation of droplet formation, which resulted in a detailed strategy to control drop size and droplet pattern formation for emulsi cation in microfluidic devices. We expect that our strategy can provide theoretical guidance to synthesize dispersion or polydisperse colloid particles.
Key words:  Microfluidic flow-focusing device, Droplet pattern formation, Transition
FundProject:
流动聚焦型微流控体系中的液滴的图案化排列和转变模式
徐华国,梁好均*
摘要:
流体在微流通道中形成剪切流场(低雷诺数).不同于宏观体系,由于剪切力和表面张力的竞争作用,产生的液滴在微尺度下的微流通道中形成特殊的排列现象---周期性类似“晶格”排列现象.设计了新型流动聚焦型微流控芯片,分析研究在微流体系中液滴周期性图案化排列和转变机理性,液滴排列模式受两方面因素影响:水油两相的流速比值和微通道尺寸.当微通道宽度为250或300 μm时,液滴形成单层分散,双层和单层挤压排列.当微通道宽度为350 μm 时,液滴会形成单层分散到三层排列到双层挤压最后到单层挤压排列.当出口通道宽度增加到400 μm时,甚至出现了液滴四层排列的现象.同时研究了各个液滴排列模式的“转变点”.
关键词:  流动聚焦型微流控,液滴图案化排列模式,转变
DOI:10.1063/1674-0068/27/06/679-684
分类号: