Study on the flow patterns and transition mechanism of the liquid-liquid two-phase flow in a step-emulsification microdevice with parallel microchannels

doi:10.11949/0438-1157.20210878

Abstract

Abstract:

The flow patterns and transition mechanism of liquid-liquid two-phase flow in a step-emulsification microdevice with parallel microchannels are studied by using a high-speed camera system. The aqueous glycerol solutions are used as the dispersed phase, and cyclohexane with the surfactant of 3% Span 85 as the continuous phase. Four flow patterns are observed under different two-phase flow conditions: dripping-dripping, transition-dripping, jetting-transition, jetting-jetting. The diagram of flow patterns is constructed with the flow rates of the two-phase as the coordinate axes, and the transition lines of the adjacent flow patterns are obtained. The transition mechanism of flow patterns is analyzed. The influences of the viscosity of the dispersed phase on the flow patterns and their transitions are investigated. The flow patterns of the liquid-liquid two-phase flow are mainly affected by the hydrodynamic feedback effect in the chamber, the operating conditions and the physical properties of fluids. As the flow rate of the dispersed phase increases, the flow pattern in the microchannel changes from the dripping to the transition flow, and finally into the jetting. With the increase of the flow rate of the continuous phase, the flow rate of the dispersed phase that changes the flow patterns increases. As the viscosity of the dispersed phase increases, the transition lines of flow patterns move downward, the region of the dripping-dripping becomes smaller, and the region of the jetting-jetting becomes larger. Finally, using the concept of mesoscale, the dynamic effects of the non-uniform structure of liquid-liquid two-phase flow in parallel microchannels are analyzed.

Key words: parallel microchannel, two-phase flow, flow pattern, microfluidics, mesoscale

摘要：

利用高速摄像仪研究了台阶式并行微通道内液液两相流流型及其转变机理。以甘油水为分散相、含3% Span 85的环己烷为连续相，观测到了滴状-滴状流、过渡-滴状流、喷射-过渡流和喷射-喷射流4种流型；以两相流量为坐标轴绘制了流型图，并获得了流型转变线；分析了流型的转变机理。考察了分散相黏度对流型及其转变的影响机制。随着分散相黏度的增大，流型转变线整体向下移动，滴状-滴状流区域变小，喷射-喷射流区域变大。最后，运用介尺度概念分析了并行微通道内液液两相流非均匀结构的动态效应。

关键词: 并行微通道, 两相流, 流型, 微流体学, 介尺度

CLC Number:

TQ 021.1

Wei ZHAN, Xiyang LIU, Chunying ZHU, Youguang MA, Taotao FU. Study on the flow patterns and transition mechanism of the liquid-liquid two-phase flow in a step-emulsification microdevice with parallel microchannels[J]. CIESC Journal, 2022, 73(1): 184-193.

湛伟, 刘西洋, 朱春英, 马友光, 付涛涛. 台阶式并行微通道内液液两相流流型及其转变机理[J]. 化工学报, 2022, 73(1): 184-193.

Figures/Tables 8

Table 1 Physical properties of various fluids used in the experiment

溶液	ρ/(kg·m^-3)	μ/(mPa·s)	σ/(mN·m^-1)
水	998.2	0.99	9.52
30%甘油水溶液	1072.8	2.45	7.79
50%甘油水溶液	1126.2	5.90	6.76
环己烷+3%Span 85	783.6	1.06	—

Fig.1 Schematic diagram of microchannel device

Fig.2 Schematic diagram of experimental apparatus

Fig.3 Droplet flow patterns corresponding to different flow rate of the dispersed phase

Fig.4 Flow patterns diagram and the transition lines in microchannel

Fig.5 Analogy diagram of fluid resistance and circuit resistance: The pressure drop between entrance A of channel 1 and exit C of channel 1 is denoted as ΔP1 and the corresponding resistance is denoted as R1; The pressure drop between entrance A of channel 2 and exit B of channel 2 is denoted as ΔP2 and the corresponding resistance is denoted as R2; The pressure drop between outlet B of channel 2 and outlet C of channel 1 is denoted as ΔP3 and the corresponding resistance is denoted as R3; R4 represents the resistance between the outlet of microchannel 1 and the chamber outlet

Fig.6 The interfacial evolution during droplet formation in the two parallel microchannels: example 1

Fig.7 The interfacial evolution during droplet formation in the two parallel microchannels: example 2

References 40

1	陈光文, 袁权. 微化工技术[J]. 化工学报, 2003, 54(4): 427-439.
	Chen G W, Yuan Q. Micro-chemical technology[J]. Journal of Chemical Industry and Engineering (China), 2003, 54(4): 427-439.
2	Poe S L, Cummings M A, Haaf M P, et al. Solving the clogging problem: precipitate-forming reactions in flow[J]. Angewandte Chemie International Edition, 2006, 45(10): 1544-1548.
3	李韦华, 张昱, 孟昊, 等. 微通道中液-液萃取传质特性的研究[J]. 化学工业与工程, 2013, 30(4): 36-41.
	Li W, Zhang Y, Meng H, et al. Mass transfer characteristics of liquid-liquid extraction in microchannel[J]. Chemical Industry and Engineering, 2013, 30(4): 36-41.
4	Carvalho I T, Estevinho B N, Santos L. Application of microencapsulated essential oils in cosmetic and personal healthcare products—a review[J]. International Journal of Cosmetic Science, 2016, 38(2): 109-119.
5	Shibata H, Heo Y J, Okitsu T, et al. Injectable hydrogel microbeads for fluorescence-based in vivo continuous glucose monitoring[J]. Proceedings of the National Academy of Sciences of the United States of America, 2010, 107(42): 17894-17898.
6	Schwartz J A, Vykoukal J V, Gascoyne P R. Droplet-based chemistry on a programmable micro-chip[J]. Lab on a Chip, 2004, 4(1): 11-17.
7	Lignos I, Protesescu L, Stavrakis S, et al. Facile droplet-based microfluidic synthesis of monodisperse Ⅳ-Ⅵ semiconductor nanocrystals with coupled in-line NIR fluorescence detection[J]. Chemistry of Materials, 2014, 26(9): 2975-2982.
8	Sathyan A, Yang Z F, Bai Y, et al. Simultaneous “clean-and-repair” of surfaces using smart droplets[J]. Advanced Functional Materials, 2019, 29(5): 1805219.
9	Fu T T, Ma Y G, Funfschilling D, et al. Squeezing-to-dripping transition for bubble formation in a microfluidic T-junction[J]. Chemical Engineering Science, 2010, 65(12): 3739-3748.
10	Zhang Q D, Li H J, Zhu C Y, et al. Micro-magnetofluidics of ferrofluid droplet formation in a T-junction[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018, 537: 572-579.
11	Chakraborty I, Ricouvier J, Yazhgur P, et al. Microfluidic step-emulsification in axisymmetric geometry[J]. Lab on a Chip, 2017, 17(21): 3609-3620.
12	Garstecki P, Stone H A, Whitesides G M. Mechanism for flow-rate controlled breakup in confined geometries: a route to monodisperse emulsions[J]. Physical Review Letters, 2005, 94(16): 164501.
13	Du W, Fu T T, Zhang Q D, et al. Self-similar breakup of viscoelastic thread for droplet formation in flow-focusing devices[J]. AIChE Journal, 2017, 63(11): 5196-5206.
14	Zhang C, Fu T T, Zhu C Y, et al. Dynamics of bubble formation in highly viscous liquids in a flow-focusing device[J]. Chemical Engineering Science, 2017, 172: 278-285.
15	Li Z, Leshansky A M, Metais S, et al. Correction: step-emulsification in a microfluidic device[J]. Lab on a Chip, 2015, 15(14): 3095.
16	Shui L L, Berg A, Eijkel J C T. Scalable attoliter monodisperse droplet formation using multiphase nano-microfluidics[J]. Microfluidics and Nanofluidics, 2011, 11(1): 87-92.
17	Postek W, Kaminski T S, Garstecki P. A passive microfluidic system based on step emulsification allows the generation of libraries of nanoliter-sized droplets from microliter droplets of varying and known concentrations of a sample[J]. Lab on a Chip, 2017, 17(7): 1323-1331.
18	Ofner A, Mattich I, Hagander M, et al. Controlled massive encapsulation via tandem step emulsification in glass[J]. Advanced Functional Materials, 2019, 29(4): 1806821.
19	Vladisavljević G T, Khalid N, Neves M A, et al. Industrial lab-on-a-chip: design, applications and scale-up for drug discovery and delivery[J]. Advanced Drug Delivery Reviews, 2013, 65(11/12): 1626-1663.
20	Stoffel M, Wahl S, Lorenceau E, et al. Bubble production mechanism in a microfluidic foam generator[J]. Physical Review Letters, 2012, 108(19): 198302.
21	Amstad E, Chemama M, Eggersdorfer M, et al. Robust scalable high throughput production of monodisperse drops[J]. Lab on a Chip, 2016, 16(21): 4163-4172.
22	Ofner A, Moore D G, Rühs P A, et al. High-throughput step emulsification for the production of functional materials using a glass microfluidic device[J]. Macromolecular Chemistry and Physics, 2017, 218(2): 1600472.
23	Xu X N, Yuan H J, Song R Y, et al. High aspect ratio induced spontaneous generation of monodisperse picolitre droplets for digital PCR[J]. Biomicrofluidics, 2018, 12(1): 014103.
24	Schuler F, Schwemmer F, Trotter M, et al. Centrifugal step emulsification applied for absolute quantification of nucleic acids by digital droplet RPA[J]. Lab on a Chip, 2015, 15(13): 2759-2766.
25	Mittal N, Cohen C, Bibette J, et al. Dynamics of step-emulsification: from a single to a collection of emulsion droplet generators[J]. Physics of Fluids, 2014, 26(8): 082109.
26	Eggersdorfer M L, Seybold H, Ofner A, et al. Wetting controls of droplet formation in step emulsification[J]. PNAS, 2018, 115(38): 9479-9484.
27	Sugiura S, Nakajima M, Seki M. Effect of channel structure on microchannel emulsification[J]. Langmuir, 2002, 18(15): 5708-5712.
28	Sugiura S, Nakajima M, Tong J H, et al. Preparation of monodispersed solid lipid microspheres using a microchannel emulsification technique[J]. Journal of Colloid and Interface Science, 2000, 227(1): 95-103.
29	刘子炜, 戴诗逸, 段聪, 等. 台阶式单微通道内气泡生成动力学[J]. 化工学报, 2020, 71(2): 552-565.
	Liu Z W, Dai S Y, Duan C, et al. Dynamics of bubble formation in single step-type microchannel[J]. CIESC Journal, 2020, 71(2): 552-565.
30	Sugiura S, Nakajima M, Iwamoto S, et al. Interfacial tension driven monodispersed droplet formation from microfabricated channel array[J]. Langmuir, 2001, 17(18): 5562-5566.
31	Wang M, Kong C, Liang Q S, et al. Numerical simulations of wall contact angle effects on droplet size during step emulsification[J]. RSC Advances, 2018, 8(58): 33042-33047.
32	Dijke K, Kobayashi I, Schroën K, et al. Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification[J]. Microfluidics and Nanofluidics, 2010, 9(1): 77-85.
33	Vladisavljević G T, Kobayashi I, Nakajima M. Generation of highly uniform droplets using asymmetric microchannels fabricated on a single crystal silicon plate: effect of emulsifier and oil types[J]. Powder Technology, 2008, 183(1): 37-45.
34	Liu Z W, Liu X Y, Jiang S K, et al. Effects on droplet generation in step-emulsification microfluidic devices[J]. Chemical Engineering Science, 2021, 246: 116959.
35	Mi S, Jiang S K, Zhu C Y, et al. Mesoscale effect on bubble formation in step-emulsification devices with two parallel microchannels[J]. AIChE Journal, 2021, 67(1): e17075.
36	Fu T T, Ma Y G, Li H Z. Hydrodynamic feedback on bubble breakup at a T-junction within an asymmetric loop[J]. AIChE Journal, 2014, 60(5): 1920-1929.
37	李静海, 胡英, 袁权. 探索介尺度科学: 从新角度审视老问题[J]. 中国科学: 化学, 2014, 44(3): 277-281.
	Li J H, Hu Y, Yuan Q. Mesoscience: exploring old problems from a new angle[J]. Scientia Sinica (Chimica), 2014, 44(3): 277-281.
38	Li J H. Exploring the logic and landscape of the knowledge system: multilevel structures, each multiscaled with complexity at the mesoscale[J]. Engineering, 2016, 2(3): 276-285.
39	Hashimoto M, Shevkoplyas S S, Zasońska B, et al. Formation of bubbles and droplets in parallel, coupled flow-focusing geometries[J]. Small, 2008, 4(10): 1795-1805.
40	Zhang Z W, Jiang S K, Zhu C Y, et al. Bubble formation in a step-emulsification microdevice with parallel microchannels[J]. Chemical Engineering Science, 2020, 224: 115815.

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