Microelectrode array

1. A microelectrode comprising:

a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use,

wherein the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

2. A microelectrode according to claim 1 , wherein the body includes more than one region of electrically conducting material and the passage passes through the body of electrically non-conducting material and through the regions of electrically conducting material.

3. A microelectrode according to claim 1 or claim 2 , wherein the region or regions are in the form of a layer or layers.

4. A microelectrode according to claim 1 , wherein the body comprises a layered structure comprising at least two spaced layers of non-conducting material and at least one layer of conducting material sandwiched between the layers of non-conducting material and at least one passage formed through the layers in a direction transverse to the layers.

5. A microelectrode according to claim 4 , wherein each layer has a thickness in a range of 5 to 1000 microns.

6. A microelectrode according to claim 4 , wherein a total thickness of the layered structure is in a range of 50 to 3000 microns.

7. A microelectrode according to claim 1 , where the passage is an analysis passage.

8. A microelectrode according to claim 1 , wherein the body has a plurality of passages passing through it and through the region or regions of electrically conducting material.

9. A microelectrode according to claim 8 , wherein the passages form a regular array.

10. A microelectrode according to claim 9 , wherein the passages form an irregular array.

11. A microelectrode according to claim 10 , wherein a dopant concentration is uniform through a conductive layer such that a dispersion of dopant when viewed over a whole volume of the electrode is such that the concentration of dopant atoms, as measured by SIMS, in any 1 mm 3 volume does not vary from the concentration of dopant atoms in any other 1 mm 3 volume by more than about 50%.

12. A microelectrode according to claim 8 , wherein all the passages have a circular cross-section.

13. A microelectrode according to claim 12 , wherein all the passages have the same diameter.

14. A microelectrode according to claim 12 , wherein a diameter of the passages is in a range of 5 microns to 10 mm.

15. A microelectrode according to claim 8 , wherein the passages are all separate from one another.

16. A microelectrode according to claim 15 , wherein a separation between passages is at least twice a diameter of the passages.

17. A microelectrode according to claim 16 , wherein a separation between passages is at least three times a diameter of the passages.

18. A microelectrode according to claim 8 , wherein one or more of the passages intersect another passage or passages.

19. A microelectrode according to claim 18 , wherein one or more intersection passages intersect one or more analysis passages.

20. A microelectrode according to claim 1 , wherein the electrically conducting diamond is boron doped diamond.

21. A microelectrode according to claim 1 , wherein the diamond is CVD or HPHT diamond.

22. A microelectrode according to claim 21 , wherein a dopant concentration is uniform such that the concentration of dopant atoms on an analysis surface(s) of a conducting layer, as measured by SIMS, in any 0.36 mm 2 area of an analysis area, does not vary from the concentration of dopant atoms in any other 0.36 mm 2 of an analysis area by more than about 50%.

23. A microelectrode according to claim 21 , wherein a dopant concentration is uniform such that the concentration of dopant atoms on any surface of a conducting layer, as measured by SIMS, in any 0.36 mm 2 area, does not vary from the concentration of dopant atoms in any other 0.36 mm 2 of area by more than about 50%.

24. A microelectrode according to to claim 21 , wherein a dopant concentration is uniform across all conductive layers in the device.

25. A microelectrode according to claim 21 , wherein, where the conductive region or layer comprises boron doped single crystal diamond, all the passages traverse a single growth sector.

26. A microelectrode array according to claim 25 , wherein, where the conductive region comprises boron doped single crystal diamond, all the analysis passages traverse a single growth sector.

27. A microelectrode according to claim 21 , wherein, where the diamond of the one or more conductive layers or regions is polycrystalline boron doped diamond, a typical grain size (modal grain size) of the diamond is less than 0.5 times a diameter of the one or more passages.

28. A microelectrode according to claim 1 , wherein the region or regions of electrically conducting material are in electrical contact with an external surface of the body.

29. An electrochemical cell which includes a microelectrode according to claim 1 .

30. A microelectrode according to claim 1 , wherein the device is adapted to be operated with a fluid flow velocity through the one or more passages of greater than 10 ms −1 .

31. A microelectrode according to claim 1 , wherein the device is adapted to be operated with a differential pressure between front and back surfaces of greater than about 0.05 MPa.

32. A microelectrode according to claim 1 , wherein the microelectrode is a micro-electro-osmotic pump.

33. A microelectrode according to claim 1 , further comprising:

separately addressable layers.

34. A microelectrode according to claim 1 , further comprising:

separately addressable regions.

35. A microelectrode according to claim 34 , further comprising:

separately addressable regions and separately addressable layers within the same microelectrode.

36. A microelectrode according to claim 1 , further comprising:

a reference electrode as an in-situ device.

37. A microelectrode according to claim 36 , wherein the reference electrode is fabricated on a surface of the microelectrode.

38. A method comprising:

applying a voltage on certain conductive layers of a microelectrode, the applied voltage being varied with time causing a fluid in passages to be pumped along the passages,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

39. A method comprising:

processing a fluid either as part of an analysis or as an alternative to the analysis by a microelectrode,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

40. A method comprising:

processing a fluid for use external to a microelectrode structure,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

41. A method comprising:

modifying a fluid by electrical means by a microelectrode,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

42. A method comprising:

modifying a fluid by electrochemical means by a microelectrode,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

43. A method comprising:

modifying a fluid by means of mixing by a microelectrode,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.

44. A method comprising:

modifying a fluid by means of dispersion into liquid droplets suspended in a gas by a microelectrode,

wherein the microelectrodes comprises a body formed from electrically non-conducting material and including at least one region of electrically conducting material and at least one passage extending through the body of non-conducting material and the region of conducting material, the electrically conducting region presenting an area of electrically conducting material to a fluid flowing through the passage in use, and the electrically conducting material is electrically conducting diamond and the non-conducting material is non-conducting diamond.