22 January 2007 Stochastic time-of-flight flow rate measurement for microfluidic applications
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We describe a thermal time of flight liquid flow rate measurement based on injection of a pseudo-random sequence of thermal tracers in a microfluidic flow stream, followed by downstream detection of the temperature variation. The cross correlation function between the injected sequence and the detected signal displays a peak corresponding to the time of flight, which in turn provides a sensitive measure of flow rate. We demonstrate the technique by using integrated MEMS silicon structures suspended across a microfluidic channel for both heating and detection. The encapsulation technique we use involves 3-layer glass-silicon-glass bonding. We are capable of measuring flow rate over more than three decades with an accuracy of a few percent (the exact measurement range scales with geometry, in our case corresponding to 5 - 10,000 µl/min). Our technique shows excellent agreement between measurement, theory and numerical simulation results; by comparison with other existing methods for microfluidic flow metering (anemometric, coriolis), ours has the advantage of being largely independent of physical fluid properties. In addition, the suspended MEMS heaters we fabricate can also be used as regular anemometer probes, extending the measurement possibilities to gas flow metering and phase detection.
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Dan E. Angelescu, Dan E. Angelescu, Jacques Jundt, Jacques Jundt, Jerome Durivault, Jerome Durivault, Thibaud Desbarbieux, Thibaud Desbarbieux, Bruno Mercier, Bruno Mercier, "Stochastic time-of-flight flow rate measurement for microfluidic applications", Proc. SPIE 6465, Microfluidics, BioMEMS, and Medical Microsystems V, 64650X (22 January 2007); doi: 10.1117/12.710029; https://doi.org/10.1117/12.710029


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