Strain monitoring system and apparatus

Abstract

A system for monitoring strain as an indicator of biological conditions, such as spinal fusion, glucose levels, spinal loading, and heart rate, includes an inter-digitated capacitor sensor, an 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.

1 . (canceled) 
     
     
         2 . A strain sensor system for detecting strain, comprising:
 a sensor configured to sense strain in a spinal implant;   a transmitter in communication with the sensor and configured to receive information representative of the strain sensed by the sensor; and   an antenna in communication with the transmitter and configured to transmit the information representative of the strain sensed by the sensor to a receiving device, wherein each of the sensor, the transmitter, and the antenna is configured to be implanted in a biological host.   
     
     
         3 . The strain sensor system according to  claim 2 , wherein the transmitter includes:
 a voltage controlled oscillator; and   a radio frequency power amplifier.   
     
     
         4 . The strain sensor system according to  claim 3 , wherein the voltage controlled oscillator is a ring oscillator. 
     
     
         5 . The strain sensor system according to  claim 2 , wherein the transmitter has an operating frequency of 100 GHz. 
     
     
         6 . The strain sensor system according to  claim 2 , wherein the transmitter is at least one of a frequency modulation transmitter or a radio frequency transmitter. 
     
     
         7 . The strain sensor system according to  claim 2 , wherein the antenna is a microstrip antenna. 
     
     
         8 . The strain sensor system according to  claim 7 , 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.   
     
     
         9 . The strain sensor system according to  claim 2 , further comprising a power supply configured for inductive coupling to a power source, the power supply being coupled to the sensor and the transmitter, wherein the power supply is configured for implantation in a biological host. 
     
     
         10 . The strain sensor system according to  claim 9 , wherein the power supply includes:
 an inductive coil;   a rectifier coupled to the inductive coil; and   a regulator coupled to the rectifier.   
     
     
         11 . The strain sensor system according to  claim 2 , wherein the sensor includes at least one finger. 
     
     
         12 . The strain sensor system according to  claim 11 , further comprising:
 a first base having a first set of fingers of the at least one finger 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 at least one finger extending therefrom.   
     
     
         13 . The strain sensor system according to  claim 11 , wherein a length of the at least one finger is 200 micrometers or less. 
     
     
         14 . The strain sensor system according to  claim 2 , wherein the antenna is configured to wirelessly transmit the information representative of the strain sensed by the sensor to a receiving device disposed outside of the biological host. 
     
     
         15 . The strain sensor system according to  claim 2 , wherein the sensor is configured to sense the strain in response to movement of the spinal implant. 
     
     
         16 . A method of detecting strain in a spinal implant, comprising:
 coupling a spinal implant to a spine, the spinal implant having a strain sensor system coupled thereto;   sensing a strain in the spinal implant with the strain sensor system;   transmitting information representative of the sensed strain to an antenna of the strain sensor system using a transmitter of the strain sensor system; and   transmitting the information representative of the sensed strain from the antenna to a receiving device.   
     
     
         17 . The method according to  claim 16 , further comprising determining a progress of spinal fusion of the at least two vertebrae using the information representative of the sensed strain received by the receiving device. 
     
     
         18 . The method according to  claim 16 , further comprising inductively coupling a sensor of the strain sensor system to a power supply, the strain in the spinal implant being sensed by the sensor. 
     
     
         19 . The method according to  claim 16 , wherein the antenna wirelessly transmits the information representative of the sensed strain to the receiving device. 
     
     
         20 . The method according to  claim 16 , wherein at least one finger of the strain sensor system senses the strain in the spinal implant. 
     
     
         21 . The method according to  claim 16 , wherein the strain sensor senses the strain in the spinal implant in response to movement of the spine.