摘要：采用差分动态显微技术研究颗粒布朗运动的基本原理, 对亚微米颗粒在纯水中的布朗运动进行实验研究;使用白光光源、高速相机以及显微镜获得颗粒图像, 并借助数据分析软件对原始图像进行处理。研究结果表明:1) 空域分析, 差分信号随时间间隔的变化趋势能够反映颗粒由于布朗运动逐渐远离初始位置的过程;2) 频域分析, 不同波矢所对应的差分信号, 其随时间间隔的变化趋势与空域结果一致, 并且不同波矢对应的特征时间, 随波矢值的增大而减小;3) 定量计算颗粒在纯水中的扩散系数, 实验结果与采用斯托克斯-爱因斯坦公式计算的无限大空间单个颗粒理论扩散系数的偏差为4.6%, 能够正确反映亚微米颗粒的布朗运动特征。

关键词：布朗运动；差分动态显微技术；扩散系数

Abstract：The principle of DDM was introduced and used to study the Brownian motion of sub-micro particles in water. A white light, a high speed camera and a microscope were used to obtain particle images experimentally. The analysis software was employed to process the original images. The experimental results show that 1) in the spatial domain, with increasing the delay time, the increase trend of differential signal reflects the particles rearrangement due to their Brownian motion. 2) In the frequency domain, with increasing the delay time, the increase trend of differential signal corresponding to different wave vector is in good agreement with that in the spatial domain. Furthermore, the characteristic time corresponding to different wave vector decreases with increasing the wave vector. 3) The deviation between calculated diffusion coefficient of particles in water and the theoretically expected values based on the Stokes-Einstein equation is 4.6%. The experimental results can reflect Brownian motion characteristics of sub-micro particles accurately.

Keywords: Brownian motion；differential dynamic microscopy；diffusion coefficient