Microfluidic bulk flow determinations based on converting heat tracer measurements
First Claim
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1. A method of measuring on-chip fluid flow within a microfabricated device comprising:
- introducing a heat tracer into a fluid flowing within a passageway of said microfabricated device, including defining a start region for determining a propagation rate of said heat tracer within said passageway;
monitoring a condition of said fluid during passage through an interrogation region;
based on said monitoring, detecting when said heat tracer reaches said interrogation region, thereby acquiring information relevant to said propagation rate of said heat tracer from said start region to said interrogation region; and
determining a bulk flow rate of said fluid through said passageway on a basis of said detecting and on a basis of an adjustment that is specific to a scaling between said bulk flow rate and said propagation rate of said heat tracer, said scaling being representative of a flow rate differential between said bulk flow rate and said propagation rate of said heat tracer.
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Abstract
The fluid flow rate within a microfluidic passageway of a microfabricated device is determined by measuring the time-of-flight of a heat pulse coupled into the fluid. Since the propagation velocity of the heat trace is generally slower than the mean flow rate of the flow, additional processing provides the appropriate scaling needed to obtain an accurate fluid flow rate measurement. The scaling factor is based on the geometry of the structure and the thermal properties of the fluid and the materials used for the device.
58 Citations
24 Claims
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1. A method of measuring on-chip fluid flow within a microfabricated device comprising:
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introducing a heat tracer into a fluid flowing within a passageway of said microfabricated device, including defining a start region for determining a propagation rate of said heat tracer within said passageway;
monitoring a condition of said fluid during passage through an interrogation region;
based on said monitoring, detecting when said heat tracer reaches said interrogation region, thereby acquiring information relevant to said propagation rate of said heat tracer from said start region to said interrogation region; and
determining a bulk flow rate of said fluid through said passageway on a basis of said detecting and on a basis of an adjustment that is specific to a scaling between said bulk flow rate and said propagation rate of said heat tracer, said scaling being representative of a flow rate differential between said bulk flow rate and said propagation rate of said heat tracer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for monitoring flow comprising:
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a substrate having integrated microfluidic features, including a microfluidic passageway having an entrance coupled to receive a flow of fluid;
a heat generator coupled to introduce heat tracers into said flow of fluid;
a detector positioned to detect temperature-dependent variations in said fluid along said microfluidic passageway, said detector having an output indicative of said temperature-dependent variations; and
a processor connected to said detector to receive said output, said processor being configured to determine tracer propagation transit times of said heat tracers through said microfluidic passageway and to determine bulk fluid flow rates through said microfluidic passageway, said tracer propagation transit times being based on data that includes said output of said detector, said bulk fluid flow rates being based on said tracer propagation transit times and a pre-identified scaling between tracer propagation rates of said microfluidic passageway and said bulk fluid flow rates of said microfluidic passageway, said pre-defined scaling being representative of a differential in correlating said tracer propagation rates to said bulk fluid flow rates. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of measuring on-chip fluid flow comprising:
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providing a microfabricated system having microfluidic features integrated with electronic circuitry onto a substrate, said microfluidic features including a microfluidic passageway having an interrogation region;
storing passageway data indicative of passageway-related factors relevant to determining a difference between a speed of fluid through said microfluidic passageway and a propagation speed of a heat pulse of fluid through said microfluidic passageway;
storing fluid data indicative of fluid-related factors relevant to determining said difference;
inducing a flow of fluid through said microfluidic passageway;
introducing a heat pulse into said flow;
determining a propagation speed of said heat pulse within said microfluidic passageway; and
converting said propagation speed of said heat pulse to a speed of said flow by using said passageway data and said fluid data. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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Specification