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

研究了一种利用双光镊和锁相法测量胶体悬浮液中原位瞬时粒子间力的方法。测量原理将通过实验进行测试，确定最小镊子间距、粒子间分离距离的测量精度、力测量的动态范围、光镊引起的粒子发热的减少。通过将实验测量结果与斯托克斯的阻力预测结果进行比较，测试将重点关注两个粒子之间的流体动力学相互作用。一个球体（直径1-2微米）将被强力镊子（尺寸约为0.5至1微米）困在固定位置，另一个球体将被固定在给定距离的振荡较弱的镊子中。激光的波长为1.06微米，以减少粒子加热。利用图像分析方法独立测量粒子间距离。所提出的方法将允许在胶体悬浮液的动态条件下进行粒子间力测量。这种测量具有根本的重要性，用其他方法是不可能做到的。如果成功，该方法将与理解广泛的工业和生物悬浮液相关。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. ***