Fluidic switches and methods for controlling flow in fluidic systems

1. A method of controlling fluid flow in a fluidic system, comprising:

providing a fluidic system, including a first fluid path having a first inlet and a second fluid path in fluid contact with the first fluid path at a fluid contact point;

flowing a fluid through the first fluid path; and

changing an aspect ratio of the first fluid path at the fluid contact point to switch at least a portion of the fluid from the first fluid path to the second fluid path at the fluid contact point.

2. A method of controlling fluid flow in a fluidic system comprising:

providing a fluidic system, including a first fluid path having a first inlet, a second inlet and a third inlet, and a second fluid path in fluid contact with the first fluid path at a fluid contact point;

supplying a process fluid to the first inlet of the first fluid path;

supplying a carrier fluid to the second inlet of the first fluid path such that the carrier fluid forces the process fluid into a first portion of the first fluid path, inhibiting switching of the process fluid to the second fluid path at the fluid contact point;

ceasing supplying the carrier fluid to the second fluid path; and

supplying the carrier fluid to the third inlet of the first fluid path such that the carrier fluid forces the process fluid into a second portion of the first fluid path, facilitating switching of the process fluid to the second fluid path at the fluid contact point.

3. A method comprising:

allowing a first fluid to flow along a first fluid path;

allowing a second fluid to flow along a second fluid path tangentially intersecting the first fluid path, the first and second fluid paths essentially free of the second and first fluids, respectively; and

manipulating a valve associated with either fluid path, diverting at least a portion of the first fluid into the second path.

4. A fluidic system, comprising:

a first fluid path having a first inlet;

a second fluid path in fluid contact with the first fluid path at a fluid contact point;

a switch for selectively controlling whether, at the fluid contact point, a portion of fluid flowing in one of the first or second fluid paths continues to flow in the same fluid path or flows into the other of the first or second fluid paths; and

a fluid flowing in at least one of the first fluid path and the second fluid path under laminar flow conditions.

5. The fluidic system of claim 4 , wherein the fluid is characterized by having a Reynolds number of less than or equal to about 10.

6. The fluidic system of claim 4 , wherein the switch comprises:

a switching region of the first fluid path proximate to the fluid contact point, the switching region including a first position corresponding to a first aspect ratio of the first fluid path and a second position corresponding to a second aspect ratio of the first fluid path.

7. The fluidic system of claim 4 , wherein the switch comprises:

a second inlet and a third inlet to the first fluid path located on either side of the first inlet;

a first fluid source connected to the first inlet;

a second fluid source distinct from the first fluid source connected to the second inlet;

a third fluid source distinct from the first fluid source connected to the third inlet; and

a metering system for selectively supplying fluid to the first fluid path from the first fluid source and one of the second fluid source and the third fluid source.

8. A microfluidic system, comprising:

a first fluid path having a first inlet;

a second fluid path in fluid contact with the first fluid path at a fluid contact point; and

a switch for selectively controlling whether, at the fluid contact point, a portion of fluid flowing in one of the first or second fluid paths continues to flow in the same fluid path or flows into the other of the first or second fluid paths;

wherein at least one of the first fluid path and the second fluid path has a cross-sectional dimension of less than about 500 μm.

9. The microfluidic system of claim 8 , wherein the switch comprises:

a switching region of the first fluid path proximate to the fluid contact point, the switching region including a first position corresponding to a first aspect ratio of the first fluid path and a second position corresponding to a second aspect ratio of the first fluid path.

10. The microfluidic system of claim 9 , wherein the first aspect ratio is greater than the second aspect ratio.

11. The microfluidic system of claim 9 , wherein the first aspect ratio is selected to inhibit transfer of fluid from the first fluid path to the second fluid path.

12. The microfluidic system of claim 9 , wherein the second aspect ratio is selected to promote transfer of fluid from the first fluid path to the second fluid path.

13. The microfluidic system of claim 9 , wherein the first aspect ratio of the first fluid path is greater than about 1.

14. The microfluidic system of claim 9 , wherein the second aspect ratio of the first fluid path is less than about 1.

15. The microfluidic system of claim 9 , wherein the switching region of the first fluid path is constructed of a flexible material.

16. The microfluidic system of claim 15 , wherein the switching region of the first fluid path is constructed of an elastomer.

17. The microfluidic system of claim 8 , wherein the switch comprises:

a second inlet and a third inlet to the first fluid path located on either side of the first inlet;

a first fluid source connected to the first inlet;

a second fluid source distinct from the first fluid source connected to the second inlet;

a third fluid source distinct from the first fluid source connected to the third inlet; and

a metering system for selectively supplying fluid to the first fluid path from the first fluid source and one of the second fluid source and the third fluid source.

18. The microfluidic system of claim 17 , wherein the first fluid source is a source of a process fluid and the second fluid source and third fluid source are sources of a carrier fluid.

19. The microfluidic system of claim 8 , wherein the first fluid path is substantially rectangular in cross-section.

20. The microfluidic system of claim 8 , wherein the second fluid path crosses the first fluid path at the fluid contact point, defining a crossing angle.

21. The microfluidic system of claim 20 , wherein the first fluid path and second fluid path partially overlap at the fluid contact point.

22. The microfluidic system of claim 21 , wherein the first fluid flow path and the second flow path are tangential to one another at the fluid contact point.

23. The microfluidic system of claim 20 , wherein the crossing angle is between about 5 and about 175 degrees.

24. The microfluidic system of claim 23 , wherein the crossing angle is between about 30 and about 150 degrees.

25. The microfluidic system of claim 24 , wherein the crossing angle is between about 45 and about 135 degrees.

26. The microfluidic system of claim 20 , wherein the crossing angle is about 90 degrees.

27. The microfluidic system of claim 8 , wherein at least one of the first fluid path and the second fluid path has a cross-sectional dimension of less than about 300 μm.

28. The microfluidic system of claim 27 , wherein at least one of the first fluid path and the second fluid path has a cross-sectional dimension of less than about 100 μm.

29. The microfluidic system of claim 28 , wherein at least one of the first fluid path and the second fluid path has a cross-sectional dimension of less than about 50 μm.

30. The microfluidic system of claim 8 , wherein both the first fluid path and the second fluid path have a cross-sectional dimension of less than about 500 μm.

31. The microfluidic system of claim 8 , wherein both the first fluid path and the second fluid path include respective portions upstream and downstream of the fluid contact point.