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

全内反射显微术（TIRM）是一种新技术 其允许测量 单个胶体颗粒和平板。 在这 技术中，激光束被反射离开载玻片， 小入射角，使光线不折射 但只是反射。 这种完全内部的 反射产生一个消逝波， 垂直于表面。 一种含有胶体的溶液 将封闭在腔室中的颗粒置于玻璃上， 滑动，并且胶体颗粒散射渐逝波。 散射强度随时间呈指数衰减。 颗粒与壁的分离距离。 的 用光电倍增管测量散射强度， 从这个测量中， 可以测量粒子与波的距离。 PI使用这种技术来测量 重力和双层力对平衡分离的影响 胶体颗粒的表面。 目前的努力 将该技术扩展到胶体力的测量 在粘性流动中。 具体而言，PI建议使用此 一种胶体颗粒板分离的测量方法 当流体流过板时的距离。 辐射 压力将被用来使球体膨胀， 可以测量散射强度，结果将 因此，对于固定的间隔距离， 流体在颗粒周围流动的胶体颗粒。 的 PI已经开发了一个电流体动力学理论， 施加在胶体颗粒上的力。 这些计算 揭示了一种升力的存在 从板壁迁移出来， 表面电荷 在没有双层力的情况下， 升力等于零。 在TIRM的帮助下， 实验，PI希望验证存在的 电动升力

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.