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学者姓名:刘赵淼
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Abstract :
微腔是一种常见的微通道结构,具有诱发流动分离形成层流涡的特性。研究微腔涡流动对理解微流控粒子分选、毛细血管生成和肺泡流动等相关微尺度流动现象具有重要意义。本文针对矩形微腔内层流涡流动及输运特性,利用显微高速摄影技术,开展了微通道主流与微腔涡流动及输运现象的染料可视化实验,探讨了染料脉线形成的"涡钩子"现象以及机理,初步揭示了微腔涡的流动及输运机理,为理解微腔流动现象及相关应用提供参考。
Keyword :
涡 涡 "涡钩子" "涡钩子" 微流控 微流控 微腔 微腔 边界线 边界线
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GB/T 7714 | 张越东 , 申峰 , 张杰 et al. 矩形微腔内“涡钩子”现象的实验研究 [C] //北京力学会第30届学术年会 . 2024 . |
MLA | 张越东 et al. "矩形微腔内“涡钩子”现象的实验研究" 北京力学会第30届学术年会 . (2024) . |
APA | 张越东 , 申峰 , 张杰 , 刘赵淼 . 矩形微腔内“涡钩子”现象的实验研究 北京力学会第30届学术年会 . (2024) . |
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Abstract :
微流控技术由于具备操控微通道中微小体积流体的能力,已成为操控粒子和细胞的新平台.基于粒子惯性迁移和微凹槽涡胞捕获的粒子分选方法,是一种重要的微流控粒子操控技术.目前,微凹槽容纳的粒子数量不高,制约了该方法的效率.为了提高微凹槽粒子容量,对圆形微凹槽进行结构设计,并利用高速显微成像技术和数值模拟,研究了不同圆形微凹槽的粒子容纳能力.研究发现,相同入口雷诺数(Re=37~555)下,带底腔的圆形微凹槽相较于普通圆形微凹槽容纳的粒子数量提升了 45%,这是因为增加底腔后使得涡流线向下延展,形成更深的"U形"结构,可以容纳更多的粒子;当Re=482 时,带底腔的直径 500 μm的圆凹槽比直径 600 μm的圆凹槽的粒子容量提高了 93.9%,原因是前者凹槽内粒子运动轨道与流线更加吻合,粒子轨道面积与凹槽面积占比达到了 97%;随着Re增加,从侧通道收集到的粒子富集浓度整体呈现先缓慢增大后减小的趋势,收集到的20 μm粒子的最大富集浓度为初始悬浮液的 126.7 倍;不同微凹槽内粒子群的轨道运动受到涡流场特性、粒子物性及粒子间相互作用和壁面限制作用等因素的共同影响.研究结果对微凹槽结构设计和提高粒子分选性能有重要指导意义.
Keyword :
粒子捕获 粒子捕获 涡胞 涡胞 微凹槽 微凹槽 微流控技术 微流控技术 粒子分选 粒子分选
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GB/T 7714 | 申峰 , 张杰 , 艾明珠 et al. 微流控粒子分选中圆形微凹槽容纳特性研究 [J]. | 力学学报 , 2024 , 56 (5) : 1317-1327 . |
MLA | 申峰 et al. "微流控粒子分选中圆形微凹槽容纳特性研究" . | 力学学报 56 . 5 (2024) : 1317-1327 . |
APA | 申峰 , 张杰 , 艾明珠 , 张越东 , 刘赵淼 . 微流控粒子分选中圆形微凹槽容纳特性研究 . | 力学学报 , 2024 , 56 (5) , 1317-1327 . |
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Abstract :
复合液滴在化工、医药和生物检测等领域有着广泛的应用,尺寸以及壳层厚度是复合液滴应用过程中的关键特征参数,研究复合液滴的动力学特性对建立相应的操控方法具有重要意义,有助于进一步实现复合液滴的按需制备.采用微流控技术制备了Y形和T形两种分岔结构,研究了双重乳化液滴(双乳液滴)在分岔结构处的流动行为.根据内、外液滴的分裂次数,将流动模式划分为二次分裂、一次分裂和不分裂 3 种.分析了流动模式的转变规律以及液滴长度对流动模式转变的影响,通过内、外液滴延伸长度、颈部宽度和缝隙宽度等特征参数的演化过程,将液滴运动过程划分为 3 个阶段,不分裂模式下为挤压、过渡和恢复,一次分裂以及二次分裂模式下为挤压、过渡和断裂,并讨论了相应的动力学机制.发现液滴长度的增加能有效降低液滴与通道之间的间隙宽度,导致双乳液滴所受的挤压力与剪切力增加,有利于液滴的分裂.基于比较成熟的单乳液滴理论,分别建立了内、外液滴的临界分裂条件,T形分岔结构的分裂临界线高于Y形,并进一步构建了内、外液滴毛细数和初始长度决定的流动模式分布图,可以很好地划分不同模式的分布区域,对于调控双乳液滴特性参数具有重要参考价值.
Keyword :
通道结构 通道结构 分裂模式 分裂模式 临界条件 临界条件 动力学特性 动力学特性 双乳液滴 双乳液滴
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GB/T 7714 | 刘赵淼 , 孙超 , 逄燕 et al. 分岔结构处双乳液滴的动力学特性研究 [J]. | 力学学报 , 2024 , 56 (5) : 1214-1222 . |
MLA | 刘赵淼 et al. "分岔结构处双乳液滴的动力学特性研究" . | 力学学报 56 . 5 (2024) : 1214-1222 . |
APA | 刘赵淼 , 孙超 , 逄燕 , 王翔 . 分岔结构处双乳液滴的动力学特性研究 . | 力学学报 , 2024 , 56 (5) , 1214-1222 . |
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Abstract :
在超疏水表面增加微凹槽结构,有利于在表面张力作用下留存部分空气形成气-液界面,从而大大降低流动阻力,在流动减阻方面展示了巨大的应用潜力.然而,由于流体剪切、空气溶解等影响,微凹槽内的空气容易发生损耗,导致气-液界面位置向凹槽底部移动,进而降低减阻效果.为了揭示微凹槽内空气损耗后气-液界面位置对流动减阻效果的影响,开展了显微高速摄影实验和计算流体动力学数值模拟,研究了微凹槽内不同气-液界面位置对两相流场特性的影响,并分析了等效滑移长度和减阻率的变化规律.结果表明,随着气-液界面位置的下移,气-液界面上方的流体从附着流转变为分离涡流,空气内部的涡流方向也从顺时针转变为逆时针.形成分离涡的临界空气损耗率为h*c=0.3~0.4,减阻率从12%降低到5%.界面下降后雷诺数Re、微通道宽度W和凹槽长度占比δ对微凹槽减阻性能也有重要影响,研究结果有助于深化对超疏水表面微凹槽两相流动减阻问题的认识,为微凹槽结构设计及应用提供重要的理论指导.
Keyword :
流动减阻 流动减阻 滑移长度 滑移长度 涡胞 涡胞 微凹槽 微凹槽 气-液界面 气-液界面
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GB/T 7714 | 申峰 , 陈杰 , 程思源 et al. 气-液界面位置对微凹槽结构内两相流场和减阻特性的影响研究 [J]. | 力学学报 , 2024 , 56 (9) : 2511-2521 . |
MLA | 申峰 et al. "气-液界面位置对微凹槽结构内两相流场和减阻特性的影响研究" . | 力学学报 56 . 9 (2024) : 2511-2521 . |
APA | 申峰 , 陈杰 , 程思源 , 逄燕 , 刘赵淼 . 气-液界面位置对微凹槽结构内两相流场和减阻特性的影响研究 . | 力学学报 , 2024 , 56 (9) , 2511-2521 . |
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Abstract :
This article investigates the equilibrium arrangement, self-assembly process, and subsequent curing of amphiphilic snowman-shaped Janus particles at the oil-water interface. The independent Janus particles are in vertical equilibrium state and the contact position of the oil-water interface is at the largest cross section of the particle's hydrophobic phase. Under the effect of the surface tension and the adsorption of materials, Janus particles may form particle combinations including the particle pairs and the particle triangle, whose inner and outer sides have the liquid surface exhibiting completely opposite contact angles. Particle combinations form stable parallel double-chain structures with diverse shapes after the self-assembly process. However, the single Janus particles attain a state of mechanical equilibrium under the influence of surrounding particles, enabling them to assemble into regular array structures. The relationship of interfacial tension coefficient between phases can be changed by adjusting the oil-water system, which leads to variations in the self-assembly speed and the final arrangement results. The thin-film with uniformly distributed vertical particles is achieved by replacing the underlying deionized water with a curing agent. Based on the understanding of the interactions between irregularly shaped Janus particles at the oil-water interface, it will be convenient to achieve the controllable self-assembly and widely applications of these particles.
Keyword :
Interaction Interaction Particle combination Particle combination Janus particles Janus particles Self-assembly Self-assembly UV light curing UV light curing
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GB/T 7714 | Pang, Yan , Li, Lin , Lou, Yi et al. Equilibrium and self-assembly of Janus particles at liquid-liquid interfaces for the film formation [J]. | COLLOIDS AND SURFACES B-BIOINTERFACES , 2024 , 244 . |
MLA | Pang, Yan et al. "Equilibrium and self-assembly of Janus particles at liquid-liquid interfaces for the film formation" . | COLLOIDS AND SURFACES B-BIOINTERFACES 244 (2024) . |
APA | Pang, Yan , Li, Lin , Lou, Yi , Wang, Xiang , Liu, Zhaomiao . Equilibrium and self-assembly of Janus particles at liquid-liquid interfaces for the film formation . | COLLOIDS AND SURFACES B-BIOINTERFACES , 2024 , 244 . |
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Abstract :
The periodic lateral migration of submicrometer cells is the primary factor leading to low precision in a spiral microchannel during cell isolation. In this study, a mathematical predictive model (PM) is derived for the lateral position of cells during the periodic lateral migration process. We analyze the relationship of migration period, migration width, and starting point of lateral migration with microchannel structure and flow conditions and determine the empirical coefficients in PM. Results indicate that the aspect ratio of the microchannel and the Reynolds number (Re) are key factors that influence the periodicity of the cell lateral migration. The lateral migration width is jointly affected by Re, the cell blockage ratio, and the microchannel curvature radius. The inlet structure of the microchannel and the ratio of the cell sample to the sheath flow rate are critical parameters for regulating the initial position. Moreover, the structure of the pressure field at the inlet constrains the distribution range of the starting point of the lateral migration. Regardless of whether the particles/cells undergo 0.5, 1, or multiple lateral migration cycles, the lateral positions predicted by PM align well with the experimental observations, thus verifying the accuracy of PM. This research helps to elucidate the characteristics of periodic lateral migration of cells in spiral microchannels and can provide practical guidance for the development and optimization of miniature spiral microchannel chips for precise cell isolation.
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GB/T 7714 | Zheng, Kai , Liu, Zhaomiao , Pang, Yan et al. Predictive Model for Cell Positioning during Periodic Lateral Migration in Spiral Microchannels [J]. | ANALYTICAL CHEMISTRY , 2024 , 96 (45) : 18230-18238 . |
MLA | Zheng, Kai et al. "Predictive Model for Cell Positioning during Periodic Lateral Migration in Spiral Microchannels" . | ANALYTICAL CHEMISTRY 96 . 45 (2024) : 18230-18238 . |
APA | Zheng, Kai , Liu, Zhaomiao , Pang, Yan , Wang, Xiang , Zhao, Siyu , Zheng, Nan et al. Predictive Model for Cell Positioning during Periodic Lateral Migration in Spiral Microchannels . | ANALYTICAL CHEMISTRY , 2024 , 96 (45) , 18230-18238 . |
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Abstract :
Molten microdroplet printing technology takes the uniform metal droplet as the basic forming unit, and it is a kind of rapid printing technology based on the shape characteristics of the parts to realize the manufacturing parts. This paper is investigated that during the microdroplet 3D printing (three-dimensional printing), electronics is studied based on the coupled level collective integral number method (coupled level set and volume of fluid) and the equivalent heat capacity method. The influence of the regional wettability characteristics of the heterogeneous functional wettability surface and its matching mode on the droplet spreading and coalescence behavior and the phase transition thermal process is explored. The precise regulation mechanism of heterogeneous functional wettability surfaces on the coalescence and forming of molten droplets is revealed. The results show that the wettability matching schemes of dual-functional-region surfaces and spaced multiple functional region surfaces can effectively regulate the dimensionless feature spreading lengths, dimensionless feature average heights, and dimensionless spreading edge spreading uniformities of the double-droplet and multiple droplet simultaneous impingement and coalescence morphologies, respectively. Under the condition of uniform wettability characteristics of the surface, the heat flow density and average temperature inside the molten fluid at the initial stage of the coalescence of double/multiple droplets show more regular symmetrical characteristics. The heat transfer effectiveness at the gap position is low and decreases with the increase in contact angle; when the surfaces are under heterogeneous bifunctional vs spaced multifunctional wettability conditions, the evolution of the overall heat transfer effectiveness of each type of wettability matching scheme increases with the increase in the wall contact angles of the single type of regions. In addition, when the surface wettability matching scheme includes a transition stage from neutral to superlyophobic, the liquid-gas interface is highly susceptible to overcoming the limitation of the energy barrier and thus instability gradually emerges, resulting in fluctuations of the heat transfer characteristics in its domain. The results of this study further enrich the droplet forming law and its phase transition heat transfer mechanism and provide a general strategy for the high-quality and high-effectiveness preparation of complex flexible electronic devices.
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GB/T 7714 | Zheng, Nan , Liu, Zhaomiao , Cai, Fanming et al. The morphology regulation mechanism during coalescence fusion printing of multiple molten droplets [J]. | PHYSICS OF FLUIDS , 2024 , 36 (10) . |
MLA | Zheng, Nan et al. "The morphology regulation mechanism during coalescence fusion printing of multiple molten droplets" . | PHYSICS OF FLUIDS 36 . 10 (2024) . |
APA | Zheng, Nan , Liu, Zhaomiao , Cai, Fanming , Zhao, Siyu , Zheng, Kai , Zhang, Chenchen et al. The morphology regulation mechanism during coalescence fusion printing of multiple molten droplets . | PHYSICS OF FLUIDS , 2024 , 36 (10) . |
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In this work, merged and alternating droplets generated in a microfluidic double T-junction are investigated using experiments and numerical simulations. The double T-junction is constructed by symmetrically inserting two capillaries into a microfluidic chip at specific positions. We explore the effects of the two-phase flow rate fraction, capillary tip distance (30 mu m, 60 mu m, and 200 mu m), and fluid properties on droplet formation phenomena. Detailed observations reveal four distinct regimes during the dynamic evolution of the two-phase interface morphology: merged state, stable alternating droplets, droplet pairs, and jetting. Two phase diagrams are obtained to demonstrate that interfacial tension and dispersed phase viscosity significantly influence these regimes. Moreover, we find that as the flow rate fraction increases from 0.054 to 0.286, the length of generated droplets increases from 156 to 789 mu m; we provide a theoretical prediction formula for dimensionless droplet length accordingly. Additionally, our simulations show fluctuating pressure in dispersed flows throughout the process of droplet generation. The simulated pressure in the dispersed flows fluctuates during the droplet generation process. The understanding of the underlying physics of the capillary-based double T-junction contributes valuable insights for various related applications.
Keyword :
Merged and alternating droplets Merged and alternating droplets Double T-junction Double T-junction Inserted capillary Inserted capillary Microfluidics Microfluidics Droplet microfluidics Droplet microfluidics
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GB/T 7714 | Shen, Feng , Zhang, Yuedong , Li, Chunyou et al. Merged and alternating droplets generation in double T-junction microchannels using symmetrically inserted capillaries [J]. | MICROFLUIDICS AND NANOFLUIDICS , 2024 , 28 (5) . |
MLA | Shen, Feng et al. "Merged and alternating droplets generation in double T-junction microchannels using symmetrically inserted capillaries" . | MICROFLUIDICS AND NANOFLUIDICS 28 . 5 (2024) . |
APA | Shen, Feng , Zhang, Yuedong , Li, Chunyou , Pang, Yan , Liu, Zhaomiao . Merged and alternating droplets generation in double T-junction microchannels using symmetrically inserted capillaries . | MICROFLUIDICS AND NANOFLUIDICS , 2024 , 28 (5) . |
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Metal foams with high porosity, light weight, and large specific surface area can significantly enhance heat transfer performance. In this study, the lattice Boltzmann method coupled with the finite difference method is used to investigate the flow boiling characteristics of metal foam surface. Focus is given on the effects of Reynolds number, gravitational acceleration, wall superheat, and metal foam thickness on heat transfer performance. Studies show that increasing the Reynolds number enhances convective heat transfer on the metal foam surface but inhibits bubble nucleation. Compared with a smooth surface, the metal foam takes full advantage of the fluid shear force induced by the high-velocity fluid in the channel-center region, thereby reducing the dependence on buoyancy for bubble detachment. As the wall superheat and metal foam thickness increase, the wake effect induced by bubble detachment is enhanced. Subsequently, bubble detachment is facilitated and the liquid supply is enhanced. These results provide theoretical and applied technical guidance for the structural design of novel metal foam surfaces.
Keyword :
Flow boiling Flow boiling Lattice Boltzmann method Lattice Boltzmann method Numerical simulation Numerical simulation Metal foam Metal foam
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GB/T 7714 | Cai, Fanming , Liu, Zhaomiao , Zheng, Nan et al. Lattice Boltzmann study of the effect of metal foam on bubble behavior and heat transfer performance in flow boiling [J]. | APPLIED THERMAL ENGINEERING , 2024 , 254 . |
MLA | Cai, Fanming et al. "Lattice Boltzmann study of the effect of metal foam on bubble behavior and heat transfer performance in flow boiling" . | APPLIED THERMAL ENGINEERING 254 (2024) . |
APA | Cai, Fanming , Liu, Zhaomiao , Zheng, Nan , Pang, Yan , Zhang, Longxiang . Lattice Boltzmann study of the effect of metal foam on bubble behavior and heat transfer performance in flow boiling . | APPLIED THERMAL ENGINEERING , 2024 , 254 . |
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The controlled motion of droplets in microfluidic chips is a preliminary requirement to realize their functions. The influence of the expansion section on the droplet motion is mainly investigated in the T-junction. The droplet dynamic characteristics are analyzed at the junction and the applicable flow rate of the expansion section is explored. The expansion section can reduce the entered length and motion time of the droplet when droplets flow into the channel with it, and finally avoid the possibility of droplet splitting. Even under a large difference of the branch flow rate, the expansion section can direct the droplet into its located channel. It is found that with the increase in continuous phase flow rate, the effect of the expansion section on the droplet motion behavior is gradually weakened until it disappears. Moreover, the critical conditions of it can be obtained by theoretical calculation. The expansion section can direct droplet motion in both symmetric and asymmetric junctions. However, it is mainly achieved by influencing the interfacial tension of the droplets in the symmetric junction, while the key force is related to the droplet motion in the asymmetric junction. Specifically, the expansion section influences the differential pressure force to direct the droplet in the flow into the side branch (with expansion section) mode, but it varies the interfacial tension of the droplet in the flow into the main branch mode.
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GB/T 7714 | Pang, Yan , Jiao, Shaojie , Zhao, Siyu et al. Droplet motions directed by an expansion section in the T-junctions [J]. | PHYSICS OF FLUIDS , 2024 , 36 (9) . |
MLA | Pang, Yan et al. "Droplet motions directed by an expansion section in the T-junctions" . | PHYSICS OF FLUIDS 36 . 9 (2024) . |
APA | Pang, Yan , Jiao, Shaojie , Zhao, Siyu , Lou, Yi , Zhang, Longxiang , Wang, Xiang et al. Droplet motions directed by an expansion section in the T-junctions . | PHYSICS OF FLUIDS , 2024 , 36 (9) . |
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