Electrokinetic Pump with Fixed Stroke Volume

• US 20090148308A1
• Filed: 12/03/2008
• Published: 06/11/2009
• Est. Priority Date: 12/11/2007
• Status: Active Grant

• Current Assignee: Teleflex Life Sciences Pte., Ltd. (Teleflex Incorporated)
• Original Assignee: Eksigent Technologies LLC
• Inventors: Saleki, Mansour A., Reis, Antonio
• Granted Patent: US 8,251,672 B2
• Time in Patent Office: Days
• US Class Current: 417/53
• CPC Class Codes: F04B 17/00 Pumps characterised by combination with, or adaptation to, specific driving engines or motors
• CPC Class Codes: F04B 43/04 Pumps having electric drive
• CPC Class Codes: F04B 43/06 Pumps having fluid drive
• CPC Class Codes: H02K 44/02 Electrodynamic pumps

Abstract

An electrokinetic pump and fluid delivery system is provided that may include any of a number of features. One feature of the fluid delivery system is that it can deliver a fixed volume of fluid with each stroke of the electrokinetic pump. Another feature of the fluid delivery system is that it can accurately deliver fluid at a target flow rate over time. Methods associated with use of the electrokinetic pump and fluid delivery system are also covered.

Claims

1. A method of pumping a fixed stroke volume of fluid with an electrokinetic pump, the method comprising:

applying a forward voltage across a pair of electrodes for a stroke period to move a fixed volume of pump fluid from a first chamber to a second chamber until the pump fluid moves a first movable member in fluid communication with the first chamber from a starting limit to an ending limit prior to lapse of the stroke period; and

causing the electrokinetic pump to occlude for a forward occlusion period greater than zero until lapse of the stroke period without degrading the pump fluid.

2. The method of claim 1 further comprising moving a second movable member in fluid communication with the pump fluid to move a fixed volume of delivery fluid through a pump outlet.

3. The method of claim 2 wherein the step of moving a second movable member comprises moving the fixed volume of delivery fluid through the pump outlet against a range of back pressures, the forward occlusion period being greatest at a lower end of the range and least at a higher end of the range.

4. The method of claim 2 wherein the second movable member is a flexible impermeable diaphragm.

5. The method of claim 2 wherein the second movable member is a piston.

6. The method of claim 1 further comprising the steps of:

applying a reverse voltage across the pair of electrodes for the stroke period to move the pump fluid from the second chamber to the first chamber until the pump fluid moves the first movable member from the ending limit to the starting limit; and

causing the electrokinetic pump to occlude for a reverse occlusion period greater than zero until lapse of the stroke period without degrading the pump fluid.

7. The method of claim 1 wherein the first movable member is a piston.

8. The method of claim 1 wherein the first movable member is a flexible impermeable diaphragm.

9. The method of claim 1 wherein the forward voltage is a square wave voltage.

10. The method of claim 1 wherein the forward voltage is applied pulsatively.

11. The method of claim 1 wherein the forward voltage is a two-step square wave voltage.

12. The method of claim 6 wherein the reverse voltage is a square wave voltage.

13. The method of claim 6 wherein the reverse voltage is applied pulsatively.

14. The method of claim 6 wherein the reverse voltage is a two-step square wave voltage.

21. The fluid delivery system of claim 13 wherein the fluid delivery cartridge further comprises a third movable member, wherein the fluid delivery cartridge is detachable from the electrokinetic pump.

15. A fluid delivery system, comprising:

an electrokinetic pump filled with a pump fluid and comprising a first chamber separated from a second chamber by a porous dielectric material disposed between a pair of capacitive electrodes, wherein the first chamber contains a first movable member in fluid communication with the pump fluid and the second chamber contains a second movable member in fluid communication with the pump fluid; and

a fluid delivery cartridge filled with a delivery fluid and comprising a compression chamber, the fluid delivery cartridge coupled to the electrokinetic pump, wherein the second movable member is disposed between the second chamber and the compression chamber, the compression chamber having a fluid inlet and a fluid outlet; and

a controller programmed to apply a forward voltage across the pair of capacitive electrodes for a stroke period to displace a fixed stroke volume of the delivery fluid from the fluid delivery cartridge through the fluid outlet.

16. The fluid delivery system of claim 15 wherein applying the forward voltage causes the second chamber to expand by the fixed stroke volume, thereby causing the compression chamber to contract by the fixed stroke volume.

17. The fluid delivery system of claim 16 wherein the second movable member extends from a retracted position to an extended position when the second chamber expands.

18. The fluid delivery system of claim 15 wherein the controller is further programmed to apply a reverse voltage across the pair of capacitive electrodes for the stroke period to draw into the fluid delivery cartridge through the fluid inlet the fixed stroke volume of the delivery fluid.

19. The fluid delivery system of claim 18 wherein applying the reverse voltage causes the second chamber to contract by the fixed stroke volume, thereby causing the compression chamber to expand by the fixed stroke volume.

20. The fluid delivery system of claim 19 wherein the second movable member collapses from an extended position to a retracted position when the second chamber contracts.

22. The fluid delivery system of claim 19 wherein the third movable member is mated to the second movable member when the fluid delivery cartridge is coupled to the electrokinetic pump.

23. The fluid delivery system of claim 15 wherein the first movable member is a piston.

24. The fluid delivery system of claim 15 wherein the first movable member is a flexible impermeable diaphragm.

25. The fluid delivery system of claim 15 wherein the second movable member is a piston.

26. The fluid delivery system of claim 15 wherein the second movable member is a flexible impermeable diaphragm.

27. The fluid delivery system of claim 15 wherein the forward voltage is a square wave voltage.

28. The fluid delivery system of claim 15 wherein the forward voltage is applied pulsatively.

29. The fluid delivery system of claim 15 wherein the forward voltage is a two-step square wave voltage.

30. The fluid delivery system of claim 18 wherein the reverse voltage is a square wave voltage.

31. The fluid delivery system of claim 18 wherein the reverse voltage is applied pulsatively.

32. The fluid delivery system of claim 18 wherein the reverse voltage is a two-step square wave voltage.

33. A method of managing an accumulated charge on a pair of capacitive electrodes in a one-directional electrokinetic pump, the method comprising:

applying a forward voltage to the pair of capacitive electrodes to move a pump fluid from a first chamber to a second chamber by electro-osmosis;

measuring the accumulated charge on the pair of capacitive electrodes;

applying a reverse voltage to the pair of capacitive electrodes when the accumulated charge exceeds a threshold value, creating an occlusion condition which discharges the pair of capacitive electrodes.

34. The method of claim 33 further comprising the step of applying the forward voltage to the pair of capacitive electrodes to resume moving the pump fluid from the first chamber to the second chamber.

35. The method of claim 33, wherein a one-way valve disposed in the second chamber creates the occlusion condition and prevents the pump fluid from moving from the second chamber to the first chamber.