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This paper presents a particle flow velocity profiler that employs in-channel electrodes with unevenly divided interelectrode gaps. The proposed electrical method measures both the particle position and velocity from the voltage signals generated by particles passing across three sensing electrodes, thus obtaining the flow velocity profile of the particles in a microfluidic channel. In this paper, we use polystyrene microparticles to characterize the performance of the present particle flow velocity profiler. At flow rates of 1.85, 2.68, and 3.60 muL/min, a flow velocity profile of 6.59-mum-diameter particles is measured with an uncertainty of 5.44%, which is comparable to the uncertainty (5%) in a previous microparticle image velocimetry. From the voltage signals for 6.59- and 5.47-mum particles, we also verify that the present device detects the particle position showing less sensitivity to particle size variation than an existing particle impedance spectroscopy. In addition, in-channel clogging detection using the present electrical method is demonstrated. The present particle flow velocity profiler offers advantages of simpler structure, cheaper cost, and higher measurement stability that is insensitive to particle size for use in integrated microbiofluidic systems.
Date of Publication: June 2008