Janus液滴是指由不同物化性质，甚至相反性质的两半部分组成的非对称多相乳液，在颜色显示、反应催化、功能材料制备等领域有着广泛的应用。液滴微流控是在微米到亚毫米尺度下精确制备和操控单分散性液滴的先进技术，是化工领域的研究热点。针对Janus液滴的复杂微尺度多相流动与混合特性，本论文实验与理论并重，从常规体系到含有高黏度离子液体的多相体系，全面研究了微通道中Janus液滴的生成、二次分裂、剪切形变以及其组分混合导致的动态界面张力对液滴行为的影响。针对非对称性Janus液滴在微通道中的生成过程，构建了三维三相颜色梯度格子玻尔兹曼模型（LBM），在常规三相体系下，对Janus液滴的结构、生成流型、尺寸以及分散相的断裂规律进行了系统的研究，揭示了在三维方形通道中分散相线的自相似减薄断裂特性。模型能为从Janus液滴结构设计出发，到微通道中的实际制备过程，在参数优化和结果预测方面提供理论指导。基于中等黏度比的离子液体-水相Janus液滴体系，采用3D打印技术制造的微通道，深入研究了Janus液滴的生成和分裂行为；结合数值模拟，印证了三种液滴分裂机制。研究发现，小液滴尺寸、低Ca数或非对称流场作用下Janus液滴将分裂出离子液体单相液滴，其分裂临界线满足液滴尺寸与Ca数的幂律关系。该工作为Janus液滴的结构调控及量产提供了研究基础。 考虑到离子液体的高黏特性，搭建了可实现O(103) 高黏度比的多相多松弛时间LBM模型，成功用于模拟高黏离子液体[BMIM][BF4]/甲苯两相流，以及[BMIM][FeCl4]-水相Janus液滴的三相流体系，揭示了剪切流场中Janus液滴的旋转角速率和形变系数随旋转角度的周期性变化特性。最后，若生成Janus液滴的二元分散相是互溶的，为探究其非对称界面张力对混合和液滴生成的影响，率先应用两相三组分颜色梯度LBM模型进行模拟，直观地展示了混合控制的动态界面张力，揭示了界面张力梯度的作用以及体系界面能的演化。研究表明，利用Janus液滴的界面张力特性，即存在的界面张力梯度，通过推动组分的再分布，能实现对混合的促进。该工作为微液滴内的混合强化提供了新思路。

Janus droplets refer to a special class of complex emulsions which are composed of two segments exhibiting asymmetrical features in physico-chemical property or morphology. They have displayed attractive applications in fields of color display, catalysis, functional material synthesis and so on. Droplet-based microfluidic technology is an advanced method to achieve the controllable preparation and precise manipulation of monodisperse microdroplets, which meets the increasingly high demand of the applications of Janus droplets. To reveal the complex flow and mixing behaviors of Janus droplets at microscale, in this dissertation, series of studies including Janus droplet formation, splitting, deformation in shear flow and the effect of dynamic interfacial tension induced by the mixing of its components were systematically conducted. Multiphase systems involving both low-viscous liquids and high-viscous ionic liquids (ILs) were investigated with the combination of experimental and the theoretical analyses. To be specific, firstly, the formation of Janus droplet in microchannel was comprehensively studied using a novel three-dimensional ternary lattice Boltzmann (LB) model. The general rules of Janus droplet morphology control, size law and dynamic collapsing of binary dispersed threads were investigated in a common system where the dispersed phases have similar physical properties. Simulation results of the ternary flow behavior are in good agreement with the reported experimental results. And, simulation revealed that the Janus dispersed threads in the three-dimensional square channel show a self-similar thinning characteristic during droplet formation. This model provides a theoretical tool for the structural design of Janus droplets and also for the optimization of preparation process in microchannels. Further experimental study was carried out on IL-aqueous binary dispersed phases with a moderate viscosity ratio difference, the formation and splitting of IL-water Janus droplets were thoroughly studied. Combined with LB simulation, three splitting flow regimes are analyzed from both experimental and theoretical aspects. It is found that the stripping of a single phasic IL droplet from the [BMIM][FeCl4]-water Janus droplet was observed under the circumstances of small droplet size, low average Ca number of the continuous phase or the formation of asymmetric flow fields. The boundary between division into two child Janus droplets and the stripping of single phasic droplets was described by the correlation between droplet effective size and Caaver number, which obeys a power law. This section provides a fundamental study for adjusting the morphology and increasing the production rate of Janus droplets in microchannels.Then, considering the high-viscous feature of most ionic liquids, multiple-relaxation-time color gradient LB model was established to simulate immiscible ternary system with viscosity ratio up to O(103). Simulation results on the flow pattern and droplet size law of the high-viscous IL [BMIM][BF4]/toluene two-phase system agreed with the experimental reports. Furthermore, the model was adopted to study the flow characteristics of Janus droplet under shear flow. Simulation results demonstrated the periodic variation of deformation coefficient and rotational angular of Janus droplet during the rotation in shear. Finally, to deeply explore the benefits of the Janus droplet, more specifically, the asymmetrical “Janus” interfacial tension distribution, for process intensification, a novel ternary LB model of binary mixtures was applied to investigate the effect of interfacial tension gradient between two miscible dispersed phases on flow behaviors and the mixing performance. Simulation results illustrated the effect of mixing-controlled dynamic interfacial tension and the evolution of interfacial energy during the mixing process inside “Janus” droplet. It is proved that the dynamic interfacial tension gradient could be used to improve mixing efficiency by promoting the redistribution of components. The results inspire a new idea for the intensification of mixing inside droplets.