Collaborative Research: An Experimental Study of the Dynamics of Heated Contact Lines Using Combined High Resolution Thermography and Interferometry

合作研究：利用高分辨率热成像和干涉测量相结合的加热接触线动力学实验研究

• 批准号: 1603339
• 负责人: Jungho Kim
• 金额: $ 21.5万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1603339&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; Study; Dynamics

An Experimental Study of the Dynamics of Heated Contact Lines Using Combined High ResolutionThermography and InterferometryUnderstanding of evaporating thin films is essential to the development of devices used in a wide variety of industries including those involved in coating, microelectronics fabrication and packaging, chemical processing, and materials development. Although there is a good theoretical understanding of how these films behave, direct measurements of both the heat transfer and the thin film thickness to verify the theoretical predictions have never been made due to the very small length scales involved. This investigation will simultaneously employ, for the first time, two very powerful and complementary experimental techniques: 1) Fluorescence techniques to measure the temperature and heat flux in the vicinity of the contact line; and 2) Multi-wavelength, image analyzing interferometry/reflectometry that enables us to determine the shape of the vapor-liquid interface, the curvature and curvature gradient of that surface, and the adsorbed film thickness ahead of the contact line. The results will contribute to making these processes more efficient, ultimately saving energy, materials, and labor costs, and will affect the design and development of many technologies that operate by controlling contact line dynamics using interfacial energy gradients (e.g., heat pipes, boiling, spreading and wetting on unheated and heated surfaces, fuel cells, evaporation induced self-assembly, micro-chemical laboratories, etc.).Many fundamental questions remain regarding the mechanisms by which energy is transferred in the interfacial region. With a completely wetting fluid, this region is characterized by a very thin adsorbed layer ahead of the contact line, by a region behind the contact line where the curvature of the vapor-liquid interface rapidly changes, and by a primary meniscus region where the curvature of the vapor-liquid interface is relatively constant. A partially wetting fluid may or may not have the adsorbed film. In addition, oscillations of the contact line have been observed in thin films on heated surfaces. The research will address fundamental phase-change heat and mass transfer questions by using interfacial energy gradients due to capillarity and disjoining pressure to naturally control the flow of simple fluids or dilute, ideal fluid mixtures. The validity of theoretical predictions regarding the structure and dynamics of the processes at the three-phase contact line will be investigated. The objectives of this work are: 1) To measure the shape of isothermal menisci using pure fluids and compare intermolecular forces obtained from those measurements with predicted values for various fluids on dielectric substrates; 2) To design, build, and operate an experiment to measure both the heat flux distribution and curvature as a function of position within the heated meniscus of pure fluids and to test current theories of interfacial transport in thin films; 3) To expand on the experiments with a pure fluid to include dilute, ideal mixtures and to test current theories of interfacial transport in thin films of mixtures; 4) To use these techniques to characterize contact line instability and oscillations for both the pure fluid and mixtures; and 5) To evaluate the degree to which molecular shape affects slip at the solid liquid interface and hence also affects transport processes in the contact line region. The fluorescence technique will allow direct measurement of the local heat flux and temperature. The interferometry/reflectometry technique will allow us to record what happens to the shape of the extended meniscus and the contact line as that energy gradient is perturbed, or to infer the local heat transfer from surface curvature measurements as the meniscus moves over the surface. Both techniques must be combined to obtain the data required to assess the current theories of interfacial transport.

对加热接触线动力学的实验研究，使用高分辨率表现和蒸发薄膜的干涉量学理解对于在各种行业中使用的设备的开发至关重要。尽管对这些薄膜的行为方式有很好的理论理解，但由于涉及非常小的长度尺度，从未对传热和薄膜厚度进行直接测量以验证理论预测。这项研究将首次同时采用两种非常强大且互补的实验技术：1）荧光技术，用于测量接触线附近的温度和热通量； 2）多波长，分析干涉法/反射仪，使我们能够确定该表面的蒸气 - 液体界面的形状，曲率和曲率梯度以及接触线之前的吸附膜厚度。结果将有助于使这些过程更加有效，最终节省能源，材料和人工成本，并会影响许多通过使用互联界能量梯度控制接触线动态来运行的许多技术的设计和开发在界面区域转移能量的机制。通过完全润湿的液体，该区域的特征是在接触线之前的一个非常薄的吸附层，在接触线后面的区域，蒸气液界面的曲率迅速变化，而原发性半月板区域则是蒸气 - 液体界面的曲率相对恒定的。部分润湿液可能会或可能没有吸附的膜。另外，在加热表面上的薄膜中观察到了接触线的振荡。该研究将通过使用界面能量梯度来解决基本的相位变化和传质问题，这是由于毛细血管和不加压力而自然控制简单流体或稀释的理想流体混合物的流动。将研究有关在三相接触线上过程的结构和动力学的理论预测的有效性。这项工作的目标是：1）使用纯流体测量等温弯月杆菌的形状，并比较从这些测量值获得的分子间力与介电底物上各种流体的预测值获得的分子间力； 2）设计，构建和操作一个实验，以测量热通量分布和曲率，这是纯流体的加热半月板中位置的函数，并测试薄膜中界面传输的当前理论； 3）用纯流体扩展实验，以包括稀释，理想的混合物，并测试混合物薄膜中界面传输的当前理论； 4）使用这些技术来表征纯流体和混合物的接触线不稳定性和振荡； 5）要评估分子形状在固体液体界面上影响滑移的程度，从而影响接触线区域中的传输过程。荧光技术将允许直接测量局部热通量和温度。干涉仪/反射仪技术将使我们能够记录延伸半月板的形状和接触线的形状，因为该能量梯度会受到干扰，或者在半月板在表面上移动时从表面曲率测量中推断出局部热传递。必须合并两种技术，以获取评估当前界面传输理论所需的数据。