Small Grant for Exploratory Research: A Novel Application of Total Internal Reflection Microscopy: Electrokinetic Lift

探索性研究小额资助：全内反射显微镜的新应用：动电升力

• 批准号: 9216077
• 负责人: Stacy Bike
• 金额: $ 5万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-01 至 1994-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9216077&HistoricalAwards=false
• 关键词: Small; Grant; Exploratory; Research; Novel

Total Internal Reflection Microscopy (TIRM) is a new technique which allows for the measurement of interaction forces between a single colloid particle and a flat plate. In this technique, a laser beam is reflected off of a glass slide at a small angle of incidence such that light is not refracted through the plate, but only reflected. This total internal reflection produces an evanescent wave which does propagate normal to the surface. A solution containing colloid particles, enclosed in a chamber, is placed on the glass slide, and the colloid particles scatter the evanescent wave. The scattering intensity decays exponentially with the separation distance of the particle from the wall. The scattering intensity is measured by a photomultiplier tube, and from this measurement, the instantaneous separation distance of the particle from the wave can be measured. The PI has used this technique to measure the effects of gravity and double layer forces on the equilibrium separation of a colloid particle from a surface. The present effort extends the technique to the measurement of colloid forces during viscous flow. Specifically, the PI proposes using this method to measure colloid particle - plate separation distances when fluid is flowing across the plate. Radiation pressure will be used to immobilize the sphere so that scattering intensity can be measured, and results will therefore be obtained for separation distances of a stationary colloid particle with fluid streaming about the particle. The PI has already developed an electrohydrodynamic theory for the forces exerted on the colloid particle. These calculations reveal the existence of a lift force which causes the sphere to migrate away from the plate wall irrespective of the surface charge. In the absence of double layer forces, this lift force is equal to zero. With the aid to the TIRM experiments, the PI hopes to verify the existence of the electrokinetic lift force.

全内反射显微镜 (TIRM) 是一种新技术，可测量单个胶体颗粒与平板之间的相互作用力。 在该技术中，激光束以小入射角从载玻片反射，使得光不会通过载玻片折射，而仅被反射。 这种全内反射产生倏逝波，该波垂直于表面传播。 将包含胶体颗粒的溶液放置在载玻片上，封闭在一个室中，胶体颗粒散射倏逝波。 散射强度随着粒子与壁的分离距离呈指数衰减。 通过光电倍增管测量散射强度，通过该测量，可以测量粒子与波的瞬时分离距离。 PI 使用该技术来测量重力和双层力对胶体颗粒与表面平衡分离的影响。 目前的工作将该技术扩展到粘性流过程中胶体力的测量。 具体来说，PI建议使用这种方法来测量流体流过板时胶体颗粒-板的分离距离。 辐射压力将用于固定球体，以便可以测量散射强度，因此可以获得静止胶体颗粒与流体在颗粒周围流动的分离距离的结果。 PI 已经开发出一种电流体动力学理论来解释作用在胶体颗粒上的力。 这些计算揭示了升力的存在，无论表面电荷如何，升力都会导致球体远离板壁迁移。 在没有双层力的情况下，该升力为零。 PI希望借助TIRM实验来验证电动升力的存在。