Modeling and simulation of droplet dynamics for microfluidic applications

저작자표시-비영리-변경금지 2.0 대한민국 이용자는 아래의 조건을 따르는 경우에 한하여 자유롭게 l 이 저작물을 복제, 배포, 전송, 전시, 공연 및 방송할 수 있습니다 다음과 같은 조건을 따라야 합니다: 저작자표시 귀하는 원저작자를 표시하여야 합니다 비영리 귀하는 이 저작물을 영리 목적으로 이용할 수 없습니다 변경금지 귀하는 이 저작물을 개작, 변형 또는 가공할 수 없습니다 l l 귀하는, 이 저작물의 재이용이나 배포의 경우, 이 저작물에 적용된 이용허락조건 을 명확하게 나타내어야 합니다 저작권자로부터 별도의 허가를 받으면 이러한 조건들은 적용되지 않습니다 저작권법에 따른 이용자의 권리는 위의 내용에 의하여 영향을 받지 않습니다 이것은 이용허락규약(Legal Code)을 이해하기 쉽게 요약한 것입니다 Disclaimer Ph.D Thesis Modeling and simulation of droplet dynamics for microfluidic applications Graduate School of Yeungnam University Department of Mechanical Engineering Major in Mechanical Engineering Van Thanh Hoang Advisor: Professor Jang Min Park, Ph.D August 2019 Ph.D Thesis Modeling and simulation of droplet dynamics for microfluidic applications Advisor: Professor Jang Min Park, Ph.D Presented as Ph.D Thesis August 2019 Graduate School of Yeungnam University Department of Mechanical Engineering Major in Mechanical Engineering Van Thanh Hoang ACKNOWLEDGMENTS I would like to dedicate this thesis for my late father who highly encouraged me to pursue a master and a doctoral program when he left this world almost nine years ago The thesis also is dedicated to the author’s mother who is seventy six years old and living far from me now I really would like to express my deepest gratitude to my thesis advisor, Professor Jang Min Park for dedicated help, valuable and devoted instructions, and everything he has done for me in academic direction and in my life as well over the last three years of my doctoral program I am so grateful to the committee members, Prof Jiseok Lim, Prof Jungwook Choi, Prof Kisoo Yoo, and Prof Kyoung Duck Seo for attending my presentation as well as providing pieces of advice for my doctoral thesis completion During my doctoral program, I wish to express my thanks to the Yeungnam University for supporting the scholarship and providing an excellent academic environment I also thank all of Lab members, Mr Gong Yao, Mr Liu Wankun, Mr Wu Yue, Mr Heeseung Lee, Mr Seung-Yeop Lee, always gave me encouragement and support during my doctoral program Finally, I would like to thank my family, especially my wife for their constant support and encouragement Date: May 15th, 2019 Van Thanh Hoang (호앙반탄) Multiphase Materials Processing Lab., ME/YU I ABSTRACT Design of microchannel geometry plays a key role for transport and manipulation of liquid droplets and contraction microchannel has been widely used for many applications in droplet-based microfluidic systems This study first aims to investigate droplet dynamics in contraction microchannel for more details and then to propose a simplified model used for microfluidic systems to describe droplet dynamics In particular, for contraction microchannel, three regimes of droplet dynamics, including trap, squeeze and breakup are characterized, which depends on capillary number (Ca) and contraction ratio (C) Theoretical models have been also proposed to describe transitions from one to another regime as a function of capillary number and contraction ratio The critical capillary number of transition from trap to squeeze has been found as a function of contraction ratio expressed as CaIc=a(CM-1), whereas critical capillary number CaIIc = c1C-1 depicts the transition from squeeze to breakup Additionally, the deformation, retraction and breakup along downstream of the contraction microchannel have been explored for more details To describe dynamics of droplet in microfluidic system, one-dimensional model based a Taylor analogy has been proposed to predict droplet deformation at steady state and transient behavior accurately The characteristic time for droplet reaching steady state is dependent on viscosity ratio and the droplet deformation at steady state is significantly influenced by viscosity ratio of which the order of II magnitude ranges from -1 to Finally, theoretical estimation of condition for droplet breakup was also proposed in the present study, which shows a good agreement with experimental result in the literature Keywords: Droplet dynamics, Microfluidics, Numerical simulation, Taylor analogy model III Contraction microchannel, TABLE OF CONTENTS ACKNOWLEDGMENTS .I ABSTRACT II TABLE OF CONTENTS IV LIST OF FIGURES VI NOMENCLATURES VIII CHAPTER INTRODUCTION 1.1 Droplet-based microfluidic system 1.2 Contraction microchannel in microfluidic system 1.3 Dynamics of droplet in contraction microchannel 1.4 Droplet dynamics in extensional flow 1.5 Problem statement 1.6 Dissertation overview CHAPTER PROBLEM DESCRIPTION 2.1 Problem description of contraction microchannel 2.2 Problem description for proposed model 2.3 Dimensionless numbers 11 CHAPTER TAYLOR ANALOGY MODELING 12 3.1 Damped spring-mass model 12 3.2 Taylor analogy breakup (TAB) model 13 3.3 Proposed model 15 3.4 Condition for droplet breakup 17 CHAPTER COMPUTATIONAL MODEL AND VALIDATION 18 4.1 Computational model and methods 18 4.2 Computational domain of contraction microchannel 19 4.3 Computational domain for the proposed model 22 4.4 Validation of simulation results in planar extensional flow 25 CHAPTER RESULTS AND DISCUSSIONS 27 5.1 Droplet dynamics in the contraction microchannel 27 5.1.1 Three regimes of the droplet dynamics 27 IV 5.1.2 Droplet dynamics along downstream of contraction microchannel 34 5.2 Performance of the proposed model 41 5.2.1 Steady behavior of droplet deformation 42 5.2.2 Transient behavior of droplet deformation 44 5.2.3 Critical capillary number for droplet breakup 45 CHAPTER CONSCLUSIONS AND RECOMMENDATIONS 47 6.1 Conclusions 47 6.2 Recommendations 48 REFERENCES 50 요약 59 CURRICULUM VITAE 61 V system As a result, droplet dynamics has been considered with various flow conditions of capillary number and viscosity ratio Furthermore, in order to compare with the model prediction, a board numerical simulation has been carried out to observe the droplet dynamics over a wide range of flow conditions The proposed model has been found in good agreement with the simulation results which was verified by previous experimental studies The characteristic time for droplet reaching steady state depends on viscosity ratio and the droplet deformation at steady state is significantly influenced by viscosity ratio when the order of magnitude of viscosity ratio ranges from -1 to Furthermore, theoretical estimation was developed to predict the critical capillary number for droplet breakup in the present study, which also shows an accurate prediction in compared with experimental result in the literature 6.2 Recommendations Modeling and simulation of dynamics of a droplet in microfluidic system have been studied Moreover, some recommendations for future studies are provided for more considerations of droplet dynamics in microfluidic systems - Dynamics of droplet in the contraction microchannel should be explored for its other aspects such as viscosity ratio, contact angle, the depth of microchannel, and contraction entrance geometries which have wedge-shaped or rounded shapes 48 As a results, critical capillary number for transition from one to another regime can be not only a function of contraction ratio but also a function of viscosity ratio - Effects of non-Newtonian fluid will be taken into account for a detailed rheological investigation in contraction microchannel - In the proposed model, future work can theoretically study droplet dynamics in two and three-dimensional shape based on the present proposed - Effects of elastic membrane on dynamics of droplet should be investigated in extensional/simple shear flow thanks to the present model - The proposed model can be applied for studies in chemistry, life science, and bioreactors where cells, vesicles are controlled as the droplet in this study - Effects of droplet shape on surface tension force (Equation (3.6)) are considered in Taylor analogy - Droplet dynamics can be extended to uniaxial and biaxial extensional flow 49 REFERENCES [1] J Castillo-León, W.E 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모세관 수와 수축률의 함수로 제안되었다 트랩에서 스퀴즈로의 전이를 설명하기 위한 중요한 모세관 수를 CaIc=a(CM-1)로 모델링 하였으며, 스퀴즈에서 해체로의 전이를 설명하기 위한 중요한 모세관 수를 CaIIc = c1C-1 로 모델링 하였다 또한, 수축 마이크로 채널의 하류를 따라 액적의 변형, 수축 및 파괴를 상세히 연구하였다 59 전체 microfluidic 시스템에서 액적의 동역학을 기술하기 위해 Taylor analogy 를 기반으로 한 차원 모델을 제안하였다 정상 상태에 도달하는 액적 거동의 특성 시간은 액적과 주변 유체의 점도 비율에 의존적임을 확인하였으며, 정상 상태에서의 액적 변형은 점도 비율의 크기 정도가 -1 에서 까지의 구간에서 가장 크게 영향을 받음을 확인하였다 마지막으로, 액적 분열 예측을 위한 이론적인 모델이 제안되었다 본 연구에서 제안된 모델의 예측값은 기존 연구의 실험 결과와 일치함을 확인하였다 Keywords : Droplet dynamics, Microfluidics, 수축 마이크로 채널, 수치 해석, Taylor analogy model 60 CURRICULUM VITAE HOANG VAN THANH (호앙반탄) Nationality: Vietnamese Email: hvthanh@dut.udn.vn Education: 2016.03-present: Ph.D candidate - School of Mechanical Engineering, Yeungnam University (YU), Republic of Korea 2010.02-2012.01: M.S - Department of Mechanical Engineering, National Taiwan University of Science and Technology (NTUST), Taiwan 2003.09-2008.06: B.S - Department of Mechanical Engineering, Danang University of Science and Technology, The University of Danang, Vietnam Publications in the Ph.D Program: Journal Van Thanh Hoang, Chan Byon, Jiseok Lim* and Jang Min Park*, Threedimensional simulation of droplet dynamics in planar contraction microchannel, Chemical Engineering Science, (2018) 176, 59-65 Van Thanh Hoang and Jang Min Park*, A Taylor analogy model for droplet dynamics in planar extensional flow, Chemical Engineering Science, (2019) 204, 27-34 Conference Van Thanh Hoang, Chan Byon, Jiseok Lim and Jang Min Park, Study on droplet dynamics through microfluidic contraction, Annual Conference of Vietnamese Young Scientists, Korea, 2017 Van Thanh Hoang, Quang Bang Tao, Duc Binh Luu, Jang Min Park*, Dynamics of a droplet at trap-squeeze transition in contraction microchannel, 17th International Symposium on Advanced Technology (ISAT-17), 2018 Previous publications: Hoang Van Thanh, Chao-Chang A Chen, Chia-Hsing Kuo, Injection molding of PC/PMMA Blend for Fabricate of the Secondary Optical Elements of LED Illumination, Advanced Materials Research, Trans Tech Publications, Switzerland, (2012), 579, 134-141 Hoang Van Thanh, Chao-Chang A Chen, Chia-Hsing Kuo, Experimental Study of Mechanical Properties of PC/PMMA blends by Injection Molding Process, The 4th International Conference on Advanced Manufacturing, ICAM (2012), 63-67 61 Van Thanh Hoang, Duc Binh Luu, Study on student engagement levels to class activities, VEEC 2015 Hoang Van Thanh, Injection Molding Technology of Optical Elements in LED Illumination, LAP LAMBERT Academic Publishing, eBook, (2013), https://www.amazon.com/Injection-Molding-Technology-ElementsIllumination/dp/3844392394 62 ...Ph.D Thesis Modeling and simulation of droplet dynamics for microfluidic applications Graduate School of Yeungnam University Department of Mechanical Engineering Major in... Van Thanh Hoang Advisor: Professor Jang Min Park, Ph.D August 2019 Ph.D Thesis Modeling and simulation of droplet dynamics for microfluidic applications Advisor: Professor Jang Min Park, Ph.D... three-dimensional numerical simulation and theoretical modeling In droplet- based microfluidic systems, dynamics of droplet in microfluidic systems is determined by the strength of the flow type which