Microfluidic mixing and dispensing

• US 20040208794A1
• Filed: 02/13/2004
• Published: 10/21/2004
• Est. Priority Date: 08/13/2002
• Status: Active Grant

• Current Assignee: Molecular BioProducts Incorporated (Perspecta, Inc.)
• Original Assignee: Nascent BioSciences Inc. (Thermo Fisher Scientific Incorporated)
• Inventors: Karg, Jeffrey A., Kroncke, Douglas W.
• Granted Patent: US 7,459,128 B2
• Time in Patent Office: Days
• US Class Current: 422/100
• CPC Class Codes: B01F 31/65 the materials to be mixed being directly submitted to a pulsating movement, e.g. by means of an oscillating piston or air column
• CPC Class Codes: B01F 33/30 Micromixers
• CPC Class Codes: B01F 35/75 Discharge mechanisms
• CPC Class Codes: B01F 35/7543 using pneumatic pressure, overpressure or gas pressure in a closed receptacle or circuit system
• CPC Class Codes: B01J 19/0046 Sequential or parallel reactions, e.g. for the synthesis of polypeptides or polynucleotides; Apparatus and devices for combinatorial chemistry or for making molecular arrays synthesis methods per se C40B50/00
• CPC Class Codes: B01J 2219/00315 Microtiter plates
• CPC Class Codes: B01J 2219/00317 Microwell devices, i.e. having large numbers of wells
• CPC Class Codes: B01J 2219/00369 in multiple or parallel arrangements
• CPC Class Codes: B01J 2219/00418 using pressure
• CPC Class Codes: B01L 2200/0605 Metering of fluids
• CPC Class Codes: B01L 2300/0829 Multi-well plates; Microtitration plates
• CPC Class Codes: B01L 2300/0838 Capillaries
• CPC Class Codes: B01L 2300/0867 Multiple inlets and one sample wells, e.g. mixing, dilution
• CPC Class Codes: B01L 2400/0406 capillary forces
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 2400/065 sliding valves
• CPC Class Codes: B01L 3/021 Pipettes, i.e. with only one conduit for withdrawing and redistributing liquids
• CPC Class Codes: G01N 2035/1039 Micropipettes, e.g. microcapillary tubes
• CPC Class Codes: G01N 35/028 having reaction cells in the form of microtitration plates
• CPC Class Codes: G01N 35/1072 with provision for selective pipetting of individual channels
• CPC Class Codes: G01N 35/1074 : arranged in a two-dimensional array
• CPC Class Codes: Y10T 436/2575 : Volumetric liquid transfer

Abstract

A microfluidic dispensing tap, such as for use in screening assays, includes a dispensing tube translatable within a sealed reservoir housing. The tube has an outer surface and defines an inner cavity open at a lower end of the tube, and a metering aperture extending through a side wall of the tube between the inner cavity and the outer surface to define a known volume. The tube is movable against a seal at a lower end of the reservoir housing between a first position, in which the metering aperture is disposed below the seal, and a second position, in which the metering aperture is disposed above the seal and exposed to the reservoir for entraining a discrete dose of a sample liquid within the aperture. An injector is configured to inject a known quantity of a diluent into the inner cavity of the tube and into fluidic contact with the dose of sample liquid in the aperture, such that the dose of sample liquid diffuses into the diluent to form a discrete mixture for dispensing from an open end of the tube.

Claims

1. A microfluidic dispensing tap, comprising

a dispensing tube having an outer surface and defining an inner cavity open at a lower end of the tube, the tube also defining a metering aperture extending through a side wall of the tube between the inner cavity and the outer surface, the metering aperture defining a known volume;

a reservoir housing defining, together with the tube outer surface, a reservoir cavity for holding a quantity of a first liquid;

a seal between the reservoir housing and the tube outer surface at a lower end of the reservoir cavity, the tube being movable against the seal between a first position, in which the metering aperture is disposed below the seal, and a second position, in which the metering aperture is disposed above the seal and exposed to the reservoir cavity for entraining a discrete dose of the first liquid within the aperture;

a tap actuator hydraulically connected to the inner cavity of the tube and configured to introduce a known quantity of a second liquid into the inner cavity of the tube and into fluidic contact with the dose of first liquid in the aperture, such that the dose of first liquid diffuses into the quantity of second liquid to form a discrete mixture for dispensing from the open end of the tube.

2. The dispensing tap of claim 1 wherein the reservoir cavity is sealed against air and light.

3. The dispensing tap of claim 1 wherein the aperture is a metering capillary and the first liquid is drawn via capillary forces into the metering capillary.

4. The dispensing tap of claim 1 wherein the actuator is adapted to cycle the solution up and down within the inner cavity of the tube to mix the first and second liquids before dispensing.

5. The dispensing tap of claim 4 wherein the solution is cycled through a mixing orifice.

6. The dispensing tap of claim 5 wherein the mixing orifice is defined at a detent in the outer surface of the tube.

7. The dispensing tap of claim 4 wherein the tap actuator is configured to perform such cycling pneumatically.

8. The dispensing tap of claim 1 further comprising means for propelling the mixed solution from the tube utilizing a compressed gas, such as air, nitrogen or argon, that engages an exposed surface of the solution.

9. The dispensing tap of claim 8 wherein the means for propelling the mixed solution from the tube comprises a compressed gas inlet port in fluid communication with inner cavity of the tube when the tube is in a dispense position.

10. The dispensing tap of claim 8 wherein the means for propelling the mixed solution from the tube comprises a compressed gas path terminating in an annular opening surrounding the lower end of the tube.

11. The dispensing tap of claim 1 wherein the second liquid is introduced into the inner cavity of the tube by injecting the second fluid into the tube at a point where the metering aperture is between the injected second fluid and said open end of the tube.

12. The dispensing tap of claim 1 wherein the second liquid is introduced into the inner cavity of the tube by being drawn up from the open end of the tube toward the metering aperture.

13. The dispensing tap of claim 1 wherein the metering aperture has a fixed volume of less than about 20 microliters, preferably between about 5 and 200 nanoliters.

14. In combination, a multiplicity of dispensing taps fashioned according to claim 1 and arranged in an array alignable with an array of wells of a microtiter plate, into each of which the mixed solution is expelled from a corresponding dispensing tap by operating the corresponding tap.

15. A device for storing and dispensing liquid into an array of wells in a multi-well container, the device comprising

an array of isolated, sealed, tapped reservoir units, each unit containing an integrated metering tap including a dispensing tube having an outer surface and defining an inner cavity open at a lower end of the tube, the tube also defining a metering capillary extending through a side wall of the tube between the inner cavity and the outer surface, the metering capillary sized to draw in a known volume of a liquid;

and

instrumentation configured to

pump a diluent along the inner cavity of the tube so that a lower meniscus edge of the diluent is below the metering capillary;

draw the liquid from the metering capillary into the diluent via diffusion or forced vacuum;

mix the liquid and diluent in the tube by hydraulically moving the diluent up and down inside the tube, to form a mixture; and

then to

expel the mixture from the tube by pumping the mixture to the end of the tube.

16. The device of claim 15 wherein the metering capillary has a fixed volume of less than about 20 microliters, preferably between about 5 and 200 nanoliters.

17. The device of claim 15 wherein the array of reservoir units is arranged so that each tap aligns with one well of a multi-well container such as a 96-well microtiter plate, a 384-well microtiter plate, a 1536-well microtiter plate or a flat plate designed to hold small amounts of fluid.

18. A method of mixing and dispensing microliter volumes of a sample liquid with a diluent liquid, the method including

providing a sealed, tapped reservoir unit containing an integrated metering tap with a dispensing tube having an outer surface and defining an inner cavity open at a lower end of the tube, the tube also defining a metering capillary extending through a side wall of the tube between the inner cavity and the outer surface;

drawing a dose volume of sample liquid into the metering capillary by capillary action;

pumping a volume of liquid diluent along the inner cavity of the tube so that a lower meniscus edge of the diluent is below the metering capillary;

drawing the dose of sample liquid from the metering capillary into the diluent via diffusion or forced vacuum;

mixing the sample liquid and diluent in the tube, to form a mixture; and

then

expelling the mixture from the tube by pumping the mixture to the end of the tube.

19. The method of claim 18 wherein the volume of liquid diluent is introduced into the inner cavity of the tube by injecting the diluent into the tube at a point where the metering aperture is between the injected diluent and said end of the tube.

20. The method of claim 18 wherein the liquid diluent is introduced into the inner cavity of the tube by being drawn up from the end of the tube toward the metering aperture.

21. The method of claim 18 wherein mixing includes hydraulically moving the diluent up and down inside the tube.

22. The method of claim 21 wherein mixing includes cycling the sample liquid and diluent through a mixing orifice.

23. The method of claim 21 wherein the diluent is moved up and down inside the tube pneumatically.

24. The method of claim 18 wherein expelling the mixture from the tube further comprises engaging an exposed surface of the mixture with a compressed gas, such as air, nitrogen or argon.