Sandia National Laboratories

Cornell Research Foundation Inc.

Cindy K Harnett

Robert Ward Crocker

Bruce P Mosier

Harold G Craighead

Kamlesh D Patel

James Frederick Stamps

Pamela F Caton

Judith L Rognlien

A device for measuring fluid flow rates over a wide range of flow rates (&#x3c;1 nL/min to &#x3e;10 &#x3bc;L/min) and at pressures at least as great as 2,000 psi. The invention is particularly adapted for use in microfluidic systems. The device operates by producing compositional variations in the fluid, or pulses, that are subsequently detected downstream from the point of creation to derive a flow rate. Each pulse, comprising a small fluid volume, whose composition is different from the mean composition of the fluid, can be created by electrochemical means, such as by electrolysis of a solvent, electrolysis of a dissolved species, or electrodialysis of a dissolved ionic species. Measurements of the conductivity of the fluid can be used to detect the arrival time of the pulses, from which the fluid flow rate can be determined. A pair of spaced apart electrodes can be used to produce the electrochemical pulse. In those instances where it is desired to measure a wide range of fluid flow rates a three electrode configuration in which the electrodes are spaced at unequal distances has been found to be desirable.

Composition pulse time-of-flight mass flow sensor

An apparatus that couples automated injection with flow feedback to provide nanoliter accuracy in controlling microliter volumes. The apparatus comprises generally a source of hydraulic fluid pressure, a fluid isolator joined to the outlet of the hydraulic pressure source and a flow sensor to provide pressure-driven analyte metering. For operation generally and particularly in microfluidic systems the hydraulic pressure source is typically an electrokinetic (EK) pump that incorporates gasless electrodes. The apparatus is capable of metering sub-microliter volumes at flowrates of 1&#x2013;100 &#x3bc;L/min into microsystem load pressures of up to 1000&#x2013;50 psi, respectively. Flowrates can be specified within 0.5 &#x3bc;L/min and volumes as small as 80 nL can be metered.

Sample preparation system for microfluidic applications

An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

Electrodes for microfluidic applications

A polycarbonate polymer such as poly(cyclohexene carbonate) acts as a positive electron beam resist, is substantially transparent to ultra violet light and that depolymerizes when heated. The polymer acts as a positive electron beam resist at 5 kV, and depolymerizes at temperatures between approximately 200-300&deg; C. The polymer is removable from underneath other layers by heating, facilitating fabrication of overhanging structures such as tubes by depositing layers on top of the polymer.

Method of using heat-depolymerizable polycarbonate sacrificial layer to create nano-fluidic devices

A device for measuring fluid flow rates over a wide range of flow rates (<1 nL/min to >10 &mgr;L/min) and at pressures at least as great as 10,000 psi. The invention is particularly adapted for use in microfluidic systems. The device operates by producing compositional variations in the fluid, or pulses, that are subsequently detected downstream from the point of creation to derive a flow rate. Each pulse, comprising a small fluid volume, whose composition is different from the mean composition of the fluid, can be created by electrochemical means, such as by electrolysis of a solvent, electrolysis of a dissolved species, or electrodialysis of a dissolved ionic species. Measurements of the conductivity of the fluid can be used to detect the arrival time of the pulses, from which the fluid flow rate can be determined

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Livermore, CA, United States of America

Cindy K Harnett