Rheology of complex fluids in micro/nanoscale passages

微/纳米通道中复杂流体的流变学

• 批准号: RGPIN-2018-05900
• 负责人: Nazemifard, Neda
• 金额: $ 2.33万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=660726
• 关键词: Rheology; complex; fluids; micro; nanoscale

Many natural or industrial fluids such as foods and beverages, pharmaceuticals, coatings, and detergents involve liquids in forms of emulsions or foams. In most cases, a dispersed liquid forms droplets in a second immiscible liquid or gas creating an interface where a thin film separates close-contact droplets. The dispersed droplets interact with each other through this thin film so it is importance to measure the physicochemical properties of these formed interfaces. Viscosity is a fundamental fluid property and is defined as the relation between stress and deformation in fluid systems. For emulsions and foams, the viscosity at the interface of liquid-liquid or liquid-gas layer can be very different from the bulk viscosity and dominates how the dispersed droplets interact with each other. That is why interfacial viscosity has been primarily linked to the long-term stability of dispersion, emulsions, and foams. Exact measurement of viscosity of interfaces is extremely challenging and is usually done by indirect methods such as addition of tracing particles that could affect the chemistry of the interfaces. Moreover, large scale measurement techniques lack the sufficient sensitivity to produce reliable measurements. ******This research program focuses on developing a nanofluidic platform coupled with total internal reflection microscopy (TIRM) as well as numerical models to directly measure the viscosity of thin liquid films without addition of any tracer particles. The nanofluidic system containing parallel channels with characteristic sizes as small as 10 nm will be fabricated to evaluate interfacial viscosity at length scales comparable to the thin film in real dispersion systems. Many-channel geometry can produce large amount of data to increase the statistical reliability of our measurement while maintaining the same experimental conditions for all the channels. Capillary forces will be used to induce the flow in nanochannels. Incorporating coating methods, the effects of wettability on apparent viscosity of the thin liquid film will be studied. TIRM microscopy will be employed to directly measure dynamic contact angle of liquids during capillary motion in the channels. A theoretical model will be developed to capture the capillary flow of both Newtonian and non-Newtonian liquids in channels. The general model will be incorporated in our experimental results to calculate thin film viscosity. ******The expected contributions from the proposed program can significantly advance our knowledge of complex liquid systems and result in developing techniques to control the stability of emulsions and dispersions according to the desired outcome. These techniques have many applications in the areas under investigation in my group, including water-in-oil emulsion stability, mixing and mass transfer in porous media during in-situ bitumen extraction, and non-aqueous bitumen extraction.**

许多天然或工业流体如食品和饮料、药品、涂料和洗涤剂涉及乳液或泡沫形式的液体。在大多数情况下，分散的液体在第二不混溶的液体或气体中形成液滴，从而产生界面，在该界面处薄膜将紧密接触的液滴分离。分散的液滴通过该薄膜彼此相互作用，因此测量这些形成的界面的物理化学性质是重要的。粘度是流体的基本性质，定义为流体系统中应力和变形之间的关系。对于乳液和泡沫，在液-液或液-气层的界面处的粘度可以与本体粘度非常不同，并且支配分散的液滴如何彼此相互作用。这就是为什么界面粘度主要与分散体、乳液和泡沫的长期稳定性有关。精确测量界面粘度极具挑战性，通常通过间接方法进行，例如添加可能影响界面化学性质的示踪颗粒。此外，大规模测量技术缺乏足够的灵敏度来产生可靠的测量。** 该研究计划的重点是开发一种与全内反射显微镜（TIRM）相结合的纳米流体平台以及数值模型，以直接测量薄液膜的粘度，而无需添加任何示踪颗粒。纳米流体系统含有平行通道的特征尺寸小至10 nm将被制造，以评估界面粘度在长度尺度可比的薄膜在真实的分散体系。多通道几何结构可以产生大量的数据，以增加我们测量的统计可靠性，同时保持所有通道的相同实验条件。毛细管力将用于诱导纳米通道中的流动。除了涂布方法外，还研究了润湿性对薄液膜表观粘度的影响。TIRM显微镜将用于直接测量通道中毛细运动期间液体的动态接触角。将开发一个理论模型，以捕获通道中的牛顿和非牛顿液体的毛细流动。一般模型将被纳入我们的实验结果来计算薄膜粘度。** 拟议计划的预期贡献可以显着提高我们对复杂液体系统的了解，并导致开发技术，以根据预期结果控制乳液和分散体的稳定性。这些技术在我的小组所研究的领域中有许多应用，包括油包水乳液稳定性，现场沥青提取过程中多孔介质中的混合和传质，以及非水沥青提取。