Electrospray emitter for microfluidic channel

• US 7,105,810 B2
• Filed: 03/21/2003
• Issued: 09/12/2006
• Est. Priority Date: 12/21/2001
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Craighead, Harold G., Kameoka, Jun
• Primary Examiner(s): WELLS, NIKITA
• Assistant Examiner(s): WELLS, NIKITA
• Application Number:
  US10/394,757
• Publication Number:
  US 20030213918A1
• Time in Patent Office: 1,271 Days
• Field of Search: 250/288, 250/281, 250/282, 210/656, 210/748, 210/198.2
• US Class Current: 250/288
• CPC Class Codes: G01N 30/6095 Micromachined or nanomachined, e.g. micro- or nanosize
• CPC Class Codes: G01N 30/7266 by electric field, e.g. electrospray
• CPC Class Codes: H01J 49/0018 Microminiaturised spectrometers, e.g. chip-integrated devices, Micro-Electro-Mechanical Systems [MEMS]
• CPC Class Codes: H01J 49/165 Electrospray ionisation

Abstract

An electrospray ionization device incorporates a shaped thin film with a microfluidic channel. The device may be interfaced to a time-of-flight mass spectrometer (TFOMS). In one embodiment, the shaped thin film has a polygonal-shaped or triangle-shaped thin polymer tip formed by lithography and etching. The microfluidic channel is approximately 20 micrometer wide and 10 micrometers deep, and embossed in a substrate using a silicon master. The shaped thin film is aligned with the channel and bonded between the channel substrate and a flat plate to create a microfluidic channel with a wicking tip protruding from the end of the channel. Application of a high voltage at one end of the channel creates an electrospray from the tip, which is provided to the TFOMS.

Claims

1. An electrospray device comprising;

a chip having a microchannel extending to an edge of the chip;

a cover; and

an emitter film having a polygonal tip sandwiched between the chip and the cover such that the polygonal tip extends from such edge of the chip.

2. The electrospray device of claim 1 and further comprising a reservoir formed in the chip and coupled to the microchannel.

3. The electrospray device of claim 1 wherein the tip of the emitter film is triangular in shape.

4. The electrospray device of claim 3 wherein the tip of the emitter film has an apex angle of between 40 and 140 degrees.

5. The electrospray device of claim 3 wherein the tip of the emitter film has an apex angle of approximately 90 degrees.

6. The electrospray device of claim 1 wherein the emitter film comprises a body portion, and a triangular tip extending from the body portion.

7. The electrospray device of claim 6 wherein the body portion is sandwiched between the chip and the cover, and has an edge substantially aligned with edges of the chip and the cover.

8. The electrospray device of claim 7 wherein the tip is located on the edge of the body that is aligned with the edges of the chip and cover, and the tip is approximately coaxial with the channel and extends from the edges.

9. The electrospray device emitter of claim 1 wherein the polygonal electrospray emitter is formed of material compatible with microfabrication techniques.

10. The electrospray device of claim 9 wherein the chip is formed of cyclo olefin polymer.

11. The device of claim 1 wherein the chip and electrospray emitter films are a single integrated piece.

12. The electrospray device of claim 11 wherein the apex is curved.

13. The electrospray device of claim 12 wherein the apex has a desired radius of curvature.

14. The electrospray device of claim 1, wherein the emitter film is formed with a triangular shape and the polygonal tip of the emitter film is curved.

15. An electrospray device comprising:

a chip having a microchannel with a first end extending to an edge of the chip;

a reservoir coupled to the microchannel;

a cover;

an emitter film haging a polygonal tip sandwiched betweenthe chip and the cover such that the polygonal tip extends from such edge of the chip; and

a power supply coupled to the reservoir.

16. The electrospray device of claim 15 and further comprising a counter electrode positioned a desired distance rom the polygonal tip.

17. The electrospray device of claim 15 wherein the polygonal electrospray emitter comprises a triangular shape or trapezoidal shape.

18. The electrospray device of claim 15 wherein the emitter film is formed of material compatibl with microfabrication techniques.

19. The nanospray emitter of claim 18 wherein the chip comprises cyclo olefin polymer.

20. An electrospray device comprising:

a chi having a microchannel with a first end extending to an edge of the chip;

a reservoir coupled to the microchannel;

a cover;

an emitter film having a polygonal tip sandwiched between the chip and the cover such that the polygonal tip extends from such edge of the chip;

a power suply coupled to the reservoir; and

a counter electrode positioned a desired distance from the polygonal tip wherein a voltage across the power supply and counter electrode causes a Taylor cone of fluid from the channel to form on the tip.

21. The electrospray device of claim 20 and further comprising a mass spectrometer having an orifice positioned opposite the Taylor cone and spaced from the tip sufficiently to receive an electrospray from the Taylor cone.

22. A method of makiong an electrospray device, the method comprising:

forming a microchannel on a substrate running to an edge of the substrate;

obtaining a thin filmemitter having a body portion with a polygonal tip on an edge of the body portion;

bonding the substrated and a cover with at least part of the body portion of thin film emitter between the substrate and cover such that the tip extends from the channel at the end of the edge of the substrate.

23. The method of claim 22 wherein the thin film emitter is formed of material compatible with microfabrication techniques.

24. The method of claim 23 wherein the substrate is formed of a cyclo olefin polymer plastic plate.

25. The method of claim 22 and further comprising creating an embossing master that is used to form the microchannel.

26. The method of claim 25, wherein the embossing master is formed from a silicon based substrate.

27. The method of claim 22 wherein the thin film emitter is obtained by patterning a polymer or silicon layer on the substrate in the shape of the desired emitter.

28. The method of claim 27 wherein the polymer or silicon layer is patterened by lithography followed by a plasma etch.

29. The method of claim 26 wherein the patterned polymer or silicon layer is peeled off the substrate in an isopropyl alcohol solution.

30. An electrospray device comprising:

a chip having a covered microfluidic structure that delivers fluid to an edge of the chip;

and

a planar emitter having a tip coupled to the edge of the chip and extending therefrom, wherein the tip has anapex shaped to facilitate formation of a Taylor cone from fluid delivered to the edge of the chip.

31. The electrospray device of claim 30 wherein the tip is triangular shaped.

32. The electrospray device of claim 30 wherein the apex is curved.

33. The electrospray device of claim 30 wherein the microfluidic structure comprises a channel, and where a width of the emitter is wider than a width of the channel.

34. The electrospray device of claim 33 wherein the emitter is approximately coaxial with the channel.

36. The microfluidic chip of claim 30, wherein the electrospray emitter is formed with a triangular shape.

37. The microfluidic chip of claim 36, wherein the electrospray emitter has a tip with an apex angle of between 40 and 140 degrees.

38. The microfluidic chip of claim 37, wherein the electrospray emitter tip has a trapezoidal configuration.

35. A microfluidic chip comprising:

a top chip portion that is formed with at least one microchannel extending to an edge of the top chip portion;

a bottom chip portion coupled to the top chip portion; and

an electrospray emitter found as a single integrated piece with the bottom chip portion, wherein the electrospray emitter extends from the ege of the top chip portion for directing an electrospray from the microfluidic chip.

39. The microfluidic chip of claim 35, wherein the electrospray emitter is approximately coaxial with the microchannel formed in the top chip portion.

40. The microfluidic chip of claim 35, wherein the electrospray emitter is formed with a triangular shape and has a curved tip.

41. The microfluidic chip of claim 40, wherein the curved tip has a small radius of curvature.

42. The microfluidic chip of claim 40 wherein the electrospray emitter has a base which extends beyond both sides of the microchannel and is approximately coaxial with the microchannel.

44. The electrospray ionization device and mass spectrometer interface as recited in claim 39, further comprising an XYZ stage that movably supports the electrospray ionization device relative to the orifice of the mass spectrometer.

43. An electrospray ionization device and mass spectrometer interface comprising:

a covered microfluidic structure formed with a reservoir in fluid communication with a microchannel that delivers fluid to an exit side of the microfluidic structure; and

an electrospray emitter extending from the edge of the microfluidic structure that is formed as a single integrated piece with at least a portion of the microfluidic structure;

a mass spectrometer having an orifice for receiving and electrospray from the emitter; and

a power supply system connected to the reservoir and a counter electrode positioned substantially adjacent to the emitter for applying a voltage to emit at least a portion of the electrospray from the emitter into the orifice of the mass spectrometer.

45. The electrospray ionization device and mass spectrometer interface as recited in claim 43, wherein the covered microfluidic structure is formed as a single piece.

46. The electrospray ionization device and mass spectrometer interface as recited in claim 43, wherein the emitter is formed with a thin-film tip.

47. An electrospray device comprising:

a covered microfluidic structure formed with a micrchannel that delivers fluid to a selected surface of the microfluidic structure; and

a wicking tip extending from the selected surface of the microfluidic structure that is formed as a single integrated place with at least a portion of the microfluidic structure, wherein the tip is configured with a predefined shape to facilitate formation of a Taylo cone when fluid is sprayed therefrom.

48. The electrospray device of claim 47 wherein the microfluidic structure includes a top portion that forms the single integrated piece with the wicking tip.

49. The electrospray device of claim 47, wherein the microfluidic structure includes a bottom portion that forms the single integrated piece with the wicking tip.

50. A device comprising:

a chip having a microchannel extending to an edge of the chip;

a cover; and

an electrospray emitter film having an apex, wherein the electrospray emitter film is sandwiched between the chip and the cover such that the apex extends from the edge of the chip.

51. The electrospray device of claim 50, wherein the apex is curved.

52. The electrospray device of claim 51 wherein the apex has a desired radius of curvature.

53. The microfluidic chip of claim 50, wherein the electrospray emitter apex has an apex angle of between 40 and 140 degrees.

54. A device comprising:

a chip having a microchannel extending to an edge of the chip;

a cover; and

emitter means extending from the edge of the chip and coupled to the microchannel for emitting an electrospray from fluid flowing through the microchannel.

55. The device of claim 54, wherein the means for emitting an electrospray creates a Taylor cone.

56. The device of claim 55 wherein the means for emitting an electrospray wicks fluid from the microchannel.

57. A device comprising:

a chip having multiple microchannels extending to an edge of the chip;

a cover; and

a plurality of electrospray emitter films, each having an apex, wherein the electrospray emitter films are disposed between the chip and the cover such that each apex extends from a microchannel at the edge of the chip.

58. The microfluidic chip of claim 57, wherein the electrospray emitter apex has an apex angle of between 40 and 140 degrees. emitter apex has an apex angle of between 40 and 140 degrees.