SUSPENDED MEMBRANE PRESSURE SENSING ARRAY

• US 20090004767A1
• Filed: 04/23/2008
• Published: 01/01/2009
• Est. Priority Date: 04/23/2007
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Sierra Scientific Instruments, Inc.
• Inventors: Parks, Thomas R., Cao, Chi
• Granted Patent: US 7,944,008 B2
• Time in Patent Office: Days
• US Class Current: 438/53
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/228 using tactile array force sensors

Abstract

An accurate and low cost macro pressure sensor is described. The pressure sensor includes an array of capacitive sensing elements formed at the intersections of sets of conductors. A lower set of conductors is supported by a substrate and an upper set of conductors is supported on a flexible polymer membrane. Capacitive sensing elements are formed where a conductor in the upper set overlaps a spacer in the lower set. Separators hold the membrane away from the substrate with a separation that, because of deflection of the membrane, varies in relation to the pressure applied to the membrane. As a result, the separation of conductors, and therefore capacitance, in each cell varies in response to the applied pressure. By attaching the membrane to the separators and optionally using slits in the membrane between capacitive sensing elements, measurements made in each capacitive sensing element can be mechanically decoupled.

Claims

1. A method of making a capacitive multidimensional sensing apparatus, the method comprising:

providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes;

orienting the membrane relative to the substrate such that each of at least two of the plurality of elongated membrane electrodes intersects each of at least two of the plurality of substrate electrodes forming a multi-dimensional array of capacitive elements, and such that open portions of the separation layer align with the capacitive elements; and

attaching the separation layer to the membrane.

2. The method of claim 1, wherein the separators comprise a non-compliant material.

3. The method of claim 1, further comprising, attaching the one or more separators to the substrate.

4. The method of claim 1, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises, depositing at least a portion of the one or more separators on the substrate.

5. The method of claim 1, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises:

providing a substrate body; and

forming grooves in the substrate body separated by ridges, wherein the ridges form at least a portion of the one or more separators.

6. The method of claim 5, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises:

providing a substrate body; and

depositing a non-conductive layer on the substrate body.

7. The method of claim 5, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises, depositing conductive films in the grooves forming substrate electrodes.

8. The method of claim 1, wherein the substrate is cylindrically shaped.

9. The method of claim 1, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises, patterning conductive electrodes on a flexible membrane using flex-circuit processing.

10. The method of claim 1, wherein the membrane comprises a polyimide and/or a polyethylene terephthalate.

11. The method of claim 1, wherein providing a substrate having a plurality of elongated substrate electrodes, a separation layer comprising one or more separators and one or more open portions, and a membrane having a plurality of elongated membrane electrodes comprises, forming a plurality of slits in the membrane.

12. The method of claim 11, wherein the slits are configured to be oriented perpendicular to an orientation of the separators.

13. The method of claim 1, further comprising, positioning spacer elements in open portions of the separation layer.

14. The method of claim 1, further comprising, removing spacer elements from open portions of the separation layer after the substrate, the separation layer, and the membrane are connected.

15. The method of claim 1, wherein the separators are not plastically deformed when the membrane is attached to the separation layer.

16. An apparatus for capacitively sensing force or pressure, the apparatus comprising:

a substrate;

a plurality of elongated substrate electrodes disposed at the substrate;

a membrane configured to deflect in response to force or pressure applied to the membrane;

a plurality of elongated membrane electrodes disposed at the membrane, wherein each of at least two of the plurality of membrane electrodes intersects each of at least two of the plurality of substrate electrodes forming a multi-dimensional array of capacitive elements having a capacitive element at each intersection; and

a plurality of separators fixedly connected with the substrate and separating the substrate and the membrane, thereby forming a plurality of sensor regions of the apparatus with sensor regions positioned between adjacent separators of the plurality of separators each including at least one capacitive element; and

wherein a membrane portion of each sensor region is mechanically decoupled from a membrane portion of each adjacent sensor region.

17. The apparatus of claim 16, wherein the membrane is attached to each separator in the plurality of separators.

18. The apparatus of claim 16, further comprising a plurality of elongated slits in the membrane, wherein each sensor region is bound by one or more separators and one or more slits.

19. The apparatus of claim 16, wherein the plurality of elongated substrate electrodes comprises a plurality of parallel elongated substrate electrodes.

20. The apparatus of claim 16, wherein the plurality of elongated membrane electrodes comprises a plurality of parallel elongated membrane electrodes.

21. The apparatus of claim 16, wherein an orientation of plurality of substrate electrodes is substantially perpendicular to an orientation of the plurality of membrane electrodes.

22. The apparatus of claim 16, wherein the plurality of separators comprises a plurality of parallel elongated separators and the sensor regions are mechanically decoupled, at least in part, by attaching the membrane to the plurality of separators.

23. The apparatus of claim 22, further comprising a plurality of elongated slits in the membrane, wherein each slit in the plurality of elongated slits is oriented perpendicular to an orientation of an elongated separator in the plurality of parallel elongated separators.

24. The apparatus of claim 16, wherein a side of the substrate facing the membrane is substantially cylindrically curved.

25. The apparatus of claim 16, wherein the substrate is cylindrical with a central substrate axis extending along a center of the cylindrical.

26. The apparatus of claim 25, wherein the membrane substantially encircles the cylindrically-shaped substrate.

27. The apparatus of claim 25, wherein the separators substantially encircle the central substrate axis.

28. The apparatus of claim 27, wherein the elongated substrate electrodes substantially encircle the central substrate axis.

29. The apparatus of claim 25, wherein the elongated membrane electrodes are substantially parallel to the central substrate axis.

30. The apparatus of claim 25, wherein:

the substrate comprises;

an outer surface comprising a plurality of grooves formed therein, each groove having a floor;

insulting layers disposed on the floors of the plurality of grooves, each of the plurality of substrate electrodes being disposed on an insulating layer;

a lumen parallel to the central substrate axis; and

a plurality of holes passing through the substrate from the lumen to a substrate electrode.

31. The apparatus of claim 30, further comprising:

a wiring harness disposed within the lumen, the wiring harness having a plurality of contact points extending therefrom, each contact point being electrically coupled through a hole of the plurality of holes to a substrate electrode.

32. The apparatus of claim 25, wherein the membrane comprises a plurality of slits.

33. The apparatus of claim 32, wherein the slits are oriented substantially parallel to the central substrate axis.

34. The apparatus of claim 25, further comprising an elastomeric sleeve encircling the central substrate axis and covering a side of the membrane facing away from the substrate.

35. The apparatus of claim 16, wherein the apparatus is cylindrical with a diameter suitable for use as an instrument to be inserted into the gastrointestinal tract of a subject.

36. The apparatus of claim 16, wherein a total area of the sensor regions of the apparatus is at least about 1 square inch.

37. The apparatus of claim 16, wherein the plurality of membrane electrodes are disposed on a side of the membrane that faces the substrate.

38. The apparatus of claim 16, further comprising an elastomeric cover adjacent to a side of the membrane that faces away from the substrate.

39. The apparatus of claim 16, wherein the membrane comprises a polyimide and/or a polyethylene terephthalate.

40. A method of operating a capacitive multi-dimensional sensing apparatus, the method comprising:

providing a multidimensional array capacitive sensing apparatus comprising;

a substrate having a plurality of substrate electrodes;

a membrane having a plurality of membrane electrodes, wherein each of at least two of the substrate electrodes intersects more than one membrane electrode in the plurality of membrane electrodes, the intersections of the membrane electrodes and the substrate electrodes forming a multidimensional array of capacitors; and

a separation layer having open portions corresponding to a plurality of sensor regions;

deflecting a first membrane portion corresponding to a first toward the substrate by stretching the first membrane portion with a first pressure while mechanically isolating membrane portions corresponding to adjacent sensor regions from a deflection of the first membrane portion; and

measuring a change in capacitance between a substrate electrode and a membrane electrode corresponding to the deflection of the first membrane portion.

41. The method of claim 40, further comprising:

deflecting a second membrane portion corresponding to a second sensor region toward the substrate by stretching the second membrane portion with a second pressure while mechanically isolating membrane portions corresponding to adjacent sensor regions from the second pressure and while deflecting the first membrane portion with the first pressure; and

measuring a change in capacitance between a substrate electrode and a membrane electrode corresponding to the deflection of the second membrane portion.