Research On Electrokinetic Microflow Measurement Based On Micro-PIV

Micro-PIV (Micro Particle Image Velocimetry) is a modification of PIV (Particle Image Velocimetry) which is a well-established technique for macroscopic flows in order to access microscale devices in the late of 1990's. It bases on modern computer technology, laser technology and digital image process technology to provide an optical, non-intrusive measurement technique permitting detailed whole flow field measurements in microscale devices.The hardware of Micro-PIV system has been developed with inverted epi-fluorescence microscope, fluorescence particle, lighting, CCD, high voltage power supply and so on. The performance parameters of hardware components are analyzed. The effective diameter in-of-plate, correlate depths with the different parameters are calculated and Brown motion error is estimated. The applied software and hardware of high voltage power supply that ranged from 0 to 8000V have been finished. The minimum output voltage resolution is 1.95V and ripple of output voltage is 3-5V.The whole Micro-PIV image process algorithm which includes image real-time collection, image pre-process, evaluation algorithm, sub-pixel algorithm and delete the wrong vectors is described. A detail analysis on the limitations such as maximum measurable displacement, spatial resolution, and velocity gradient is discussed. And a multi-spatial resolution, high-accuracy and speedy algorithm, which combined the pattern matching, multi-grid algorithm and pyramid algorithm, has been build. This algorithm is not only more accuracy than the other correlation-based algorithms but also at the expense of lower computation costs by used the pyramid algorithm. The result that evaluated the standard particle images provided by VSJ with different interrogate window shows the average displacement error less than 0.05pixel. The bias error is nearly zero; random error and total error are both less than 0.02pixel by evaluated the synthetic particle image that have known displacement at 0-1pixel and 3-4pixel.The Micro-PIV technique has been applied to measure velocities in uniform width curved microchannel that under 40V, 60V and 80V drive voltage. The top curved microchannel section and straight section have been analyzed. The results show the velocity along inner edge faster than velocity along outer edge and the average velocity is linear with the drive voltage.