Nano- and microfluidics using optical tweezers with fast single particle tracking

光镊是一种在空间上具有纳米分辨率，在实际中具有亚皮牛顿分辨率的微观流变测量工具。提出的项目有两个意图，一是对胶体和聚合物研究中的基本问题作出贡献，二是解决微纳米流体的技术问题。具体的实验计划如下：1.)测量两个孤立的单胶体之间的力-距离依赖关系，其中一个由微移液管保持，另一个由光学镊子保持。胶体之间的分离可以在纳米级上变化。2)。在涂覆和未涂覆表面的稳定状态和流体流动中测量单个胶体和壁面之间的力-距离依赖关系。3)。测量稳态和流动中不同浓度聚合物溶液和不同拓扑结构聚合物的单胶体耗竭力。4)。光阱中胶体布朗运动的涨落分析使我们能够推导出黏度的局部张量。通过这种方法，可以探索微通道或活体生物系统等非均匀微观结构。5)。测量均匀和非均匀液体在小范围几何形状中的流动剖面，如微米分离的板，微通道等，有或没有表面修饰（如疏水）。

Optical tweezers with fast single particle tracking are microscopic rheometric tools with nanometer resolution in space and subpico -newton resolution in force. The proposed project has two intentions to contribute to basic questions in colloid- and polymer-research and to address technological problems of micro- and nanofluidics. In detail the following experiments are planned: 1.) Measurements of the force-distance dependence between two isolated single colloids of which one is hold by a micro-pipette and the other by optical tweezers. The separation between the colloids can be varied in nanometer steps. 2.) Measurement of the force-distance-dependence between a single colloid and a wall in the steady state and in fluid flow for coated and uncoated surfaces. 3.) Measurement of depletion forces between single colloids in the steady state and in flow for polymer solutions of varying concentration and for polymers of different topology. 4.) A fluctuation analysis of the Brownian motion of a colloid in an optical trap enables one to deduce the local tensor of viscosity. By that inhomogeneous microscopic structures like microchannels or living biological systems can be explored. 5.) Measurement of the flow profile of homogeneous and hetereogeneous liquids in small confining geometries like plates with micrometer separation, microchannels, etc. with - and without surface modifications (e.g. hydrophobization).