(516g) Micro Electrokinetic Turbulence and Its Measurement in a Microchannel

We first report some phenomena on microelectrokinetic turbulence, which is experimentally achieved in a microchannel at relatively low Reynolds number (on the order of 1 without forcing) when a pressure driven flow is electrokinetically forced. The measured maximum Reynolds number under forcing is not higher than 100. The inlet of the flow has two streams with different electrical conductivity, and the ratio of the conductivity is 1:5000. To characterize the flow, measurement of the statistical features of the flow is required. However, conventional velocimeters, such as microPIV that uses particles as tracer, cannot measure such unsteady flows with sufficiently spatial and temporal resolution simultaneously. In addition, in electrokinetic flows, the particles have essentially different velocity from their surrounding flow. Therefore, here we apply laser induced fluorescence photobleaching anemometer (LIFPA), which uses an electrically neutral charged, small molecular dye, to measure the flow velocity to avoid these issues. Home-developed confocal LIFPA enables required simultaneously high spatial and temporal measurement. The observed microelectrokinetic turbulence can generate ultrafast mixing and LIFPA would become an promising velocimeter for accurate measurement of flow velocity in complicated flows in microfluidics, where the velocity of particles are different from that of the fluid, and simultaneously high spatial and temporal resolution is required.