Strain monitoring system and apparatus

• US 9,510,785 B2
• Filed: 05/29/2015
• Issued: 12/06/2016
• Est. Priority Date: 07/08/2004
• Status: Active Grant

• Current Assignee: Deborah Susan Munro
• Original Assignee: Deborah Munro
• Inventors: Munro, Deborah, Lee, Eunice, Ramahi, Amjad
• Primary Examiner(s): EISEMAN, ADAM JARED
• Application Number:
  US14/725,286
• Publication Number:
  US 20150265213A1
• Time in Patent Office: 557 Days
• Field of Search: 600/587, 600593-595
• US Class Current: 1/1
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 2562/0261 Strain gauges
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• 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 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/4566 Evaluating the spine A61B5/4561 takes 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 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 90/06 Measuring instruments not otherwise provided for
• CPC Class Codes: A61B 90/98 using electromagnetic means, e.g. transponders
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2002/30668 : Means for transferring electromagnetic energy to implants
• CPC Class Codes: A61F 2250/0001 : Means for transferring electromagnetic energy to implants

Abstract

A system for monitoring strain as an indicator of biological conditions, such as spinal fusion, glucose levels, spinal loading, and heart rate. The system includes an inter-digitated capacitor sensor, and RF transmitter, and an associated antenna, all of which are microminiature or microscopic in size and can be implanted in a biological host such as a human or animal. An inductively coupled power supply is also employed to avoid the need for implantation of chemical batteries. Power is provided to the sensor and transmitter, and data is transmitted from the sensor, when an external receiving device, such as a handheld RF ID type receiver, is placed proximate the location of the implanted sensor, transmitter and inductively coupled power supply. The implanted sensor, transmitter and inductively coupled power supply can be left in place permanently or removed when desired.

Claims

1. A strain sensor apparatus configured for implantation into a biological host for detecting strain, the strain sensor apparatus comprising:

a plurality of free-standing, inter-digitated fingers arranged to form an area variation inter-digitated capacitor having a capacitance, the plurality of fingers configured to be coupled to a surface in a configuration to allow movement with bending of the surface, wherein the inter-digitated capacitor is configured to change its capacitance as a result of a change in area defined between fingers of the plurality of fingers due to lateral movement of the plurality of fingers;

a transmitter coupled to the inter-digitated capacitor; and

an antenna coupled to the transmitter, each of the inter-digitated capacitor, the transmitter, and the antenna being configured for implantation in a biological host.

2. The strain sensor apparatus according to claim 1, wherein lateral movement of the plurality of fingers and the change in capacitance are linearly related.

3. The strain sensor apparatus according to claim 1, wherein the inter-digitated capacitor has a sensitivity of 10⁻

14 F.

4. The strain sensor apparatus according to claim 1, wherein the inter-digitated capacitor is disposed in a housing.

5. The strain sensor apparatus according to claim 1, wherein the transmitter includes:

a voltage controlled oscillator; and

a radio frequency power amplifier.

6. The strain sensor apparatus according to claim 5, wherein the voltage controlled oscillator is a ring oscillator.

7. The strain sensor apparatus according to claim 1, wherein the transmitter has an operating frequency of 100 GHz.

8. The strain sensor apparatus according to claim 1, wherein the transmitter is at least one of a frequency modulation transmitter or a radio frequency transmitter.

9. The strain sensor apparatus according to claim 1, wherein the antenna is a microstrip antenna.

10. The strain sensor apparatus according to claim 9, wherein the microstrip antenna includes:

a conducting ground plane;

a low-loss dielectric substrate positioned on the ground plane; and

a metallic patch positioned on the dielectric substrate.

11. The strain sensor apparatus according to claim 1, further comprising a power supply configured for inductive coupling to a power source, the power supply being coupled to the plurality of fingers and the transmitter, wherein the power supply is configured for implantation in a biological host.

12. The strain sensor apparatus according to claim 11, wherein the power supply includes:

an inductive coil;

a rectifier coupled to the inductive coil; and

a regulator coupled to the rectifier.

13. The strain sensor apparatus according to claim 1, further comprising:

a first base having a first set of fingers of the plurality of fingers extending therefrom; and

a second base laterally spaced from and in parallel alignment with the first base, the second base having a second set of fingers of the plurality of fingers extending therefrom.

14. The strain sensor apparatus according to claim 13, wherein a distance between a tip of each finger of the first set of fingers and the first base is 50 micrometers.

15. The strain sensor apparatus according to claim 1, wherein a length of each finger of the plurality of fingers is 200 micrometers or less.