Interactions between liquid flows and chemically modified microchannels

毛细管内液体流动的行为，包括流体-溶质和流体-壁面的相互作用，对于更好地理解微毛细管设备、电泳生物芯片、血液和淋巴循环、蛋白质吸附、钙化和透析中的技术和生物医学流动现象至关重要。我们的目标是研究微通道中的水、有机和生物液体流动，以及它们在受控条件下与化学修饰的壁面的相互作用。所使用的流体是均质的，例如纯溶剂或电解质，或非均相的，例如含有胶体颗粒、蛋白质或细胞的水溶液。微通道将通过深X射线光刻制造，允许自由设计横向流动几何形状。通道的宽度可以从几微米到几百纳米不等。因此，可以从连续流动条件到分子运动开始影响流动的尺度来研究系统。通道壁将通过涂覆超薄有机薄膜进行化学修饰，例如，控制通道壁的亲水性或接枝不同密度的聚合物刷子。因此，可以评估各种流体-壁面相互作用。为了分析这些系统，我们将应用同轴全息术和和频率产生光谱(SFG)。同轴全息术通过跟踪示踪剂颗粒获得微视场速度分布的详细图像，而SFG作为一种非线性光学技术对流体-壁面相互作用高度敏感，如穿透流体分子和流固界面上的有序现象。

The behavior of liquid flows in capillaries, including fluid-solute and fluid-wall interactions, is of utmost importance for the better understanding of technical and biomedical flow phenomena as found in microcapillary devices, electrophoretic biochips, blood and lymph circulation, protein adsorption, calcification, and dialysis. Our goal is to study aqueous, organic, and biological liquid flows in microchannels and their interaction with chemically modified walls under controlled conditions. The fluids used are homogeneous, e.g. pure solvents or electrolytes, or heterogeneous, e.g. aqueous solutions containing colloidal particles, proteins, or cells. The microchannels will be fabricated by deep X-ray lithography, which allows the free design of lateral flow geometries. The width of the channels can be altered from several microns to few hundred nanometers. Thereby, the systems can be studied from continuous flow conditions down to the scale, where molecular motion starts to affect the flow. The channel walls will be chemically modified by coating with ultrathin organic films, e.g., to control hydrophilicity of the walls or to graft polymer brushes of different density. Thereby, a variety of fluid-wall interactions can be assessed. For analysis of these systems we shall apply in-line holography and sum frequency generation spectroscopy (SFG). While in-line holography yields a detailed picture of the velocity distribution of the microsopic flow by tracking tracer particles, SFG as a nonlinear optical technique is highly sensitive to fluid-wall interactions, such as penetrating fluid molecules and order phenomena at the fluid-solid interface.