面向典型微流控芯片的流场测速技术研究

Research on measurement of microflow velocity field in typical microfluidic chips

介绍了微流体流动特性测试技术的发展和应用概况,选用激发光源、荧光显微镜和高精度CCD摄像机等建立了显微粒子图像测速装置,用于测量微流控芯片内部电渗流流动特性,并给出显微成像单元、激发光源、示踪粒子的技术指标和适用范围.根据微流控芯片的特征尺寸和内部电渗流速度,分析了应用显微粒子图像测速技术测量微流场速度分布的测量分辨率、测量精度、测速范围等关键问题.研究结果表明:在电场强度100V/cm、宽度50μm的玻璃微通道内,硼砂电渗流速度约为220μm/s,放大倍率低于40倍,MicroPIV动态测速范围能满足流场测速要求;选用直径300nm的荧光粒子,在高于10倍放大倍率下,粒子像大于3个CCD像元的尺寸,可以进行观测;MicroPIV测速系统的测速精度则与光学系统、图像处理技术、电场力、布朗运动等有关系.

The development and the application of measurement for microflow characteristics are generally introduced. Exciting light sources, fluorescence microscopy and high-precision CCD camera are selected to set up the MicroPIV device, which is used to measure the electroosmosis flow characteristics in microfluidic chips, and technique parameters and valid ranges on the micro-imaging unit, light resource and tracking particle are provided too. According to the feature size and the electroosmosis velocity of microfluidic chips, key problems encountered in the application of MicroPIV, such as optical resolution, measurement precision, and the range of velocity measurement are analyzed in detail. When the intensity of the electric field is equal to 100 V/cm, the electroosmosis velocity of borax solution is about 220 μm/s in a microchannel of 50 μm width and under the magnification less than 40 times, the dynamic velocity range can be suitable for measurement of the electroosmosis flow. For a fluorescence particle of 300 nm in diameter, the imaging size is larger than that of three pixels in CCD, therefore effective measurements can be obtained. The measurement precision of MicroPIV depends on parameters of microscope, electric force, image processing technique and Brownian motion.