SHIELDED CAPACITOR SENSOR SYSTEM FOR MEDICAL APPLICATIONS AND METHOD

• US 20120152036A1
• Filed: 02/27/2012
• Published: 06/21/2012
• Est. Priority Date: 06/29/2010
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Stein, Marc, Chase, Andrew
• Granted Patent: US 8,714,009 B2
• Time in Patent Office: Days
• US Class Current: 73/862.626
• CPC Class Codes: A61B 17/1615 Drill bits, i.e. rotating tools extending from a handpiece to contact the worked material
• CPC Class Codes: A61B 17/1666 for the acetabulum
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 2562/0252 Load cells
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/4509 Bone density determination
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06

Abstract

A measurement system for measuring a parameter of the muscular-skeletal system is disclosed. The measurement system comprises a capacitor, a signal generator, a digital counter, counter register, a digital clock, a digital timer, and a data register. The sensor of the measurement system is the capacitor. The measurement system generates a repeating signal having a measurement cycle that corresponds to the capacitance of the capacitor. The capacitor comprises more than one capacitor mechanically in series. Electrically, the capacitor comprises more than one capacitor in parallel. In one embodiment, the capacitor includes a dielectric layer comprising polyimide. A force, pressure, or load is applied to the capacitor that elastically compresses the device. The capacitor is shielded from parasitic coupling and parasitic capacitance.

Claims

1. An integrated medical sensor comprising an elastically compressible capacitor including a shield configured to reduce capacitive coupling to a conductive region of the capacitor.

2. The sensor of claim 1 further including interconnect coupled to the conductive region of the capacitor.

3. The sensor of claim 2 further including a shield configured to reduce capacitive coupling to the interconnect.

4. The sensor of claim 3 where the capacitor is configured to measure a force, pressure, or load.

5. The sensor of claim 4 where the force, pressure, or load compresses a dielectric layer of the capacitor.

6. The sensor of claim 3 where the shield of the capacitor and the shield of the interconnect is configured to be coupled to ground.

7. The sensor of claim 3 where the capacitor is flexible.

8. The sensor of claim 1 where the capacitor is conformal to a non-planar surface.

9. A medical device, tool, equipment, or component having a non-planar surface including a capacitor coupled to and conforming to the non-planar surface.

10. The medical device, tool, equipment, or component of claim 9 where the capacitor is elastically compressible.

11. The medical device, tool, equipment, or component of claim 10 further including an interconnect coupled to electronic circuitry where the capacitor is formed in the interconnect.

12. The medical device, tool, equipment, or component of claim 10 further including a shield configured to reduce capacitive coupling to a conductive region of the capacitor.

13. The medical device, tool, equipment, or component of claim 10 further including a shield configured to reduce capacitive coupling to interconnect from the electronic circuitry to the capacitor.

14. The medical device, tool, equipment or component of claim 10 where the capacitor comprises:

a first dielectric layer;

a first conductive region overlying the first dielectric layer; and

a second conductive region underlying the first dielectric layer where the first and second conductive regions are coupled in common.

15. The medical device, tool, equipment, or component of claim 14 further including:

a second dielectric layer overlying the first conductive layer; and

a third conductive region overlying the second dielectric layer.

16. The medical device, tool, equipment, or component of claim 14 where the third conductive region is a shield configured to reduce capacitive coupling to the first and second conductive regions of the capacitor.

17. The medical device, tool, equipment, or component of claim 16 further including:

a third dielectric layer underlying the second conductive region; and

a fourth conductive region underlying the third dielectric layer.

18. The medical device, tool, equipment, or component of claim 17 where the fourth conductive region is a shield configured to reduce capacitive coupling to the first and second conductive regions of the capacitor and where the third and fourth conductive region are coupled in common.

19. A method of sensing a force, pressure, or load comprising the steps of:

compressing a capacitor with the force, pressure, or load; and

shielding at least one conductive region of the capacitor to reduce capacitive coupling.

20. The method of claim 19 further including a step of shielding an interconnect coupling the capacitor to electronic circuitry to reduce capacitive coupling.