Experimental investigation of the free surface evolution at the moving contact line of the polymeric fluids

hossein P. Kavehpour，加州大学洛杉矶分校：该项目是一项实验研究，旨在探索聚合物流体在移动接触线附近的自由表面和纳米结构的演变。最近的理论和实验研究表明，对于高度纠缠的聚合物熔体，自由表面的形状可能会有明显的不同。一层微膜，被称为前驱体层，存在于润湿流体的移动接触线的前面。这种薄膜的结构已经在理论上进行了研究，但以前的实验研究受到测量系统（横向或垂直）的分辨率的限制，需要捕捉该特征的完整范围。高度纠缠的聚合物熔体靠近移动接触线的自由表面具有另一种类型的结构，称为“脚区”。由于高剪切应力，这种结构是由靠近移动接触线的未纠缠聚合物形成的。微观前驱膜的存在仍然是这类流体存在的一种可能性。我们的初步实验已经证明了这种结构，但还需要进一步的实验。PI将使用相移激光反馈干涉仪（psLFI）和全内反射荧光显微镜（TIR-FM）测量移动接触线附近扩散液滴轮廓的演变。psLFI系统的垂直分辨率约为10nm，横向分辨率为0.5im。该系统将在宏观和微观水平上测量自由表面的演化。TIR-FM系统可以检测到距离衬底约100nm的荧光材料。该系统通常用于单细胞分子动力学，但尚未用于接触线现象的研究。红外调频的范围和分辨率使其成为此类实验的理想工具。实验结果将与现有的理论预测进行比较。这项研究的智力价值在于，之前针对这一问题所做的大多数实验都没有适当的时间和空间分辨率来充分量化这一现象。使用psLFI和TIR-FM将提供更好地研究各种复杂流体的移动接触线所需的分辨率和动态范围。这些实验将首次揭示前驱体膜的三维结构。广泛的影响将使众多工业领域受益，从涂料和油漆行业到。此外，这笔拨款将进一步培养一名博士研究生和一名本科生研究员，从而将研究和教育结合起来。

CBET-0730251Hossein P. Kavehpour, University of California-Los AngelesThis project is an experimental investigation to probe the evolution of the free surface and nano-structures in the vicinity of the moving contact line for polymeric fluids. Recent theoretical and experimental investigations have shown that the shape of the free surface may be markedly different for highly entangled polymer melts. A microscopic film, which is known as the precursor layer, exists at the front of the moving contact line for wetting fluids. The structure of this thin film has been studied theoretically, but previous experimental investigations were limited by the resolution of the measurement system (lateral or vertical) required to capture the complete scope of this feature. The free surface close to the moving contact line of highly-entangled polymer melts features another type of structure, called the "foot region." This structure arises from formation of unentangled polymers close to the moving contact line, due to the high shear stress. The existence of the microscopic precursor film is still a possibility for these types of fluids. Our preliminary experiments have shown such structures but additional experiments are necessary. The PI will measure the evolution of the profile of a spreading droplet near the moving contact line using a phase-shifted laser feedback interferometer (psLFI) and a total internal reflection fluorescence microscope (TIR-FM). The psLFI system has the vertical resolution of approximately 10nm and lateral resolution of 0.5im. This system will measure the free surface evolution at the macroscopic and microscopic levels. The TIR-FM system can detect fluorescence materials approximately 100nm from the substrate. This system, commonly used on single cell molecule dynamics, has not been used to study the contact line phenomena. The range and resolution of the TIR-FM makes it an ideal tool for such experiments. The experimental finding will be compared with the available theoretical predictions. The intellectual merit of this investigation rests on the fact that most of the previous experiments done on this problem did not have appropriate temporal and spatial resolution to fully quantify this phenomena. Using psLFI and TIR-FM will provide resolution and dynamic range required to better investigate the moving contact line of a variety of complex fluids. These experiments will reveal three dimensional structure of precursor film for the first. The broad impact will benefit numerous industrial fields, from coating and paint industries to. In addition, this grant will further the training of a Ph.D. graduate student and an undergraduate researcher and therefore integrate research and education.