SGER: Measurement of Colloidal Forces in Situ With Dual Optical Tweezers

摘要CTS-9805887 H.D.研究了一种利用双光镊和相位锁定法测量胶体悬浮液中颗粒间瞬时力的方法。 测量原理将通过实验进行测试，以确定镊子之间的最小距离，颗粒间分离距离的测量精度，力测量的动态范围，以及减少光镊引起的颗粒加热。 测试将集中在两个粒子之间的流体动力学相互作用，通过比较实验测量斯托克斯的阻力预测。 一个球体（直径1-2微米）将被强镊子（尺寸约为0.5至1微米）捕获在固定位置，另一个球体将以给定距离固定在振荡的弱镊子中。 激光波长为1.06微米，以减少颗粒加热。 将通过使用图像分析独立测量颗粒间距离。 所提出的方法将允许在动态条件下的胶体悬浮液中的颗粒间力的测量。 这种测量具有根本的重要性，并且通过其他手段是不可能的。 如果成功的话，该方法将与理解广泛的工业和生物悬浮液有关。拟议的项目将探讨这些方法的可行性和技术限制。 ***

Abstract CTS-9805887 H.D. Ou-Yang, Lehigh University An approach to measure the in-situ instantaneous interparticle forces in colloidal suspensions using dual optical tweezers and phase lock-in methods is investigated. The principle of measurement will be tested by conducting experiments to determine the minimum distance between tweezers, the measurement accuracy of the interparticle separation distance, the dynamic range of the force measurement, and the reduction of particle heating caused by optical tweezers. The tests will focus on the hydrodynamic interactions between two particles, by comparing the experimental measurements to Stokes's drag force prediction. One sphere (1-2 microns in diameter) will be trapped in a fixed position by strong tweezers (size of about 0.5 to 1 micron), and another sphere will be held at a given distance into oscillating weaker tweezers. The laser has 1.06 micron wavelength in order to reduce particle heating. The interparticle distance will be independently measured by using image analysis. The proposed approach would allow for interparticle force measurements in dynamic conditions in colloidal suspensions. Such measurements are of fundamental importance and are not possible by other means. If successful, the method would have relevance to understanding a broad group of industrial and biological suspensions. The proposed project will explore the feasibility and the technical limits of the methods. ***