利用光学显微镜测量布朗运动

Measurement of Brownian Motion Using Optical Microscope

利用光学显微镜图像采集系统对直径为1μm的聚苯乙烯小球的布朗运动进行了测量。采集得到的图像序列利用Image J软件经过反色,然后利用单粒子跟踪算法插件进行了粒子定位操作。通过对粒子图像序列定位数据的匹配操作得到了典型的粒子布朗运动轨迹,测量得到的粒子扩散系数实验值为(0.504±0.014)μm2/s,与理论值0.522μm2/s相比较,相对误差为3.4%,基本符合良好。液体定向流动、温度测量、采集时间都会对测量结果有影响。对这些相关的实验误差来源进行了分析并指出避免定向流动,控制测量时间能够减小实验误差。

Brownian motion is the random movement of particles suspended in a fluid （a liquid or a gas）. By measuring the Brownian motion, many useful physical parameters including diffusion coefficient can be obtained. Optical microscope based CCD image acquisition system is used to measure the Brownian motion of polystyrene particle with a diameter of 1 μm. The recorded image sequences were then processed with its color reverted by Image J software, followed by positioning Brownian motion particles through Single-particle tracking plug-in. By matching the positioning data of the image sequences,typical measured particle Brownian motion trajectories were obtained. Base on the trajectory data, the diffusion coefficient value was calculated to be （0. 504 ±0. 014） μm2/s,with a relative error of 3.4 % compared to the theoretical value 0. 522 μm2/s. The directional flow of the liquid, temperature measurement and acquisition time can influence the measurement. Then, these sources of experimental error were analyzed, which indicated that avoiding directional flow and controlling acquisition time can decrease experimental errors.