双光镊测量胶体微粒间相互作用势

分析了两个存在相互作用势的胶体微粒的布朗运动,讨论了通过微粒布朗运动的显微观测来测量胶体微粒间相互作用势的实验方法。将双光镊系统与同步斩光器相结合,建立了相应的测量系统。对1μm直径的聚苯乙烯球悬浮液中两个小球之间的静电相互作用势进行了实验研究。实验结果和DLVO(Derjagin-Landau-Verwey-Overbeek)理论符合较好,为DLVO理论提供了直接的微观实验依据。对决定实验精度和效率的一些实验因素,包括测量过程中光镊的开关切换时间、光镊打开和关闭的持续时间、样品离样品池底面高度和实验测量区间划分精度等进行了具体讨论。所建立的实验装置和方法可用于测量不同类型胶体粒子间的相互作用势,这为深入研究决定分散体系宏观性质的微观基础提供了一种有效的手段。

Measurement of Interaction Potential between Colloidal Particles Using Dual Optical Tweezers

Based on the analyses of the Brownian motion of two interactive colloidal particles, the experimental method for measuring the interaction potential between two micro-scale colloidal particles was studied by making a micro observation of Brownian motion of particles. The measuring system was constructed by dual optical tweezers and a synchronized chopper. This method was used to measure the interaction potential of a pair of 1μm diameter polystyrene spheres. The consistency between the measured result and the DLVO (Derjagin-Landau-Verwey-Overbeek) theory provides direct microscopic experimental evidence to the theory. Some parameters deciding the experimetal precision and efficiency, such as the switching time, the duration of the on and the off state of the optical tweezers, the distance between the sample particles and the bottom of the sample cell, and the precision of experimental measuring interval, were discussed. The apparatus and method provide an effective technique for measuring the interaction potential between particles of different colloid system and getting an insight into the microscopic foundation for the macroscopic properties of colloids.