Strain sensor, monitoring system, and method of manufacturing thereof

Abstract

Electronic devices, apparatus, systems, and methods of operating and constructing the devices, apparatus, and/or systems include a wireless sensor configured to measure strain of hardware, which can be implanted in a subject. In various embodiments, temporal measurement of the hardware strain includes monitoring changes of the resonant frequency of the sensor. The sensor can be realized as an inductively powered device that operates as an all-on-chip resonator, where the components of the sensor are biocompatible. Additional apparatus, systems, and methods are disclosed.

What is claimed is: 
     
         1 . A strain sensor comprising:
 a substrate; and   a resonator configured as a strain gauge composed of:
 a conductive layer on the substrate in contact therewith; 
 a solid dielectric material on the conductive layer in contact therewith as a dielectric capacitor; and 
 a conductive coil on the solid dielectric material in contact therewith, 
   wherein the conductive layer, the solid dielectric material, and the conductive coil of the resonator are configured to undergo strain as strain is imparted to the substrate,   wherein the resonator is configured to be inductively powered without an incorporated power supply,   wherein the resonator is configured to reflect electromagnetic waves corresponding to a resonant frequency of the resonator in response to an alternating magnetic or electromagnetic field directed toward the strain sensor, and   wherein the resonant frequency of the resonator shifts in correspondence with the strain imparted to the substrate.   
     
     
         2 . The strain sensor of  claim 1 , wherein the substrate is flexible. 
     
     
         3 . The strain sensor of  claim 2 , wherein the flexible substrate is configured as a flexible tape. 
     
     
         4 . The strain sensor of  claim 1 , wherein the solid dielectric material is composed of silicon nitride and the conductive coil is composed of gold. 
     
     
         5 . The strain sensor of  claim 1 , wherein the solid dielectric material, the conductive layer, and the conductive coil of the resonator are composed as a metamaterial. 
     
     
         6 . The strain sensor of  claim 1 , wherein the conductive coil has one of a spiral, split-ring, or nested split-ring configuration. 
     
     
         7 . The strain sensor of  claim 6 , wherein the spiral configuration has a continuous length of conductive material with at least two spiral turns. 
     
     
         8 . The strain sensor of  claim 6 , wherein the nested split-ring configuration includes an inner square and an outer square, the outer square including a first break and the inner square including a second break, the first break being along a length of the outer square that is opposite a length of the inner square having the second break. 
     
     
         9 . The strain sensor of  claim 8 , further including an array of nested split-ring configuration. 
     
     
         10 . The strain sensor of  claim 6 , wherein the spiral coil configuration has at least two spiral turns. 
     
     
         11 . The strain sensor of  claim 6 , wherein the nested split-ring configuration has a plurality of rectangles with a common base side but having different heights, and each having a gap opposite the base side. 
     
     
         12 . The strain sensor of  claim 1 , wherein the conductive coil is configured as an array of conductive coils. 
     
     
         13 . The strain sensor of  claim 12 , wherein the array of conductive coils includes at least two different coil configurations. 
     
     
         14 . The strain sensor of  claim 1 , wherein the resonator has a suspended resonator configuration. 
     
     
         15 . The strain sensor of  claim 1 , wherein the conductive coil has a triplet configuration with each being configured as one of a rectangular spiral coil resonator, a circular spiral coil resonator, a suspended resonator, or a split-ring-resonator. 
     
     
         16 . The strain sensor of  claim 1 , wherein the resonant frequency of the resonator ranges from 50 MHz to 7 GHz at no load. 
     
     
         17 . A monitoring system comprising:
 a strain sensor comprising:
 a substrate; and 
 a resonator configured as a strain gauge composed of:
 a conductive layer on the substrate in contact therewith; 
 a solid dielectric material on the conductive layer in contact therewith as a dielectric capacitor; and 
 a conductive coil on the solid dielectric material in contact therewith, 
 
 wherein the conductive layer, the solid dielectric material, and the conductive coil of the resonator are configured to undergo strain as strain is imparted to the substrate, 
 wherein the resonator is configured to be inductively powered without an incorporated power supply, 
 wherein the resonator is configured to reflect electromagnetic waves corresponding to a resonant frequency of the resonator in response to an alternating magnetic or electromagnetic field directed toward the strain sensor, and 
 wherein the resonant frequency of the resonator shifts in correspondence with the strain imparted to the substrate; 
   an electromagnetic field generator configured to generate an alternating magnetic or electromagnetic field to power the resonator;   a receiver configured to receive electromagnetic waves reflected by the resonator in response to the resonator being excited by the generated alternating magnetic or electromagnetic field;   a spectrum analyzer configured to determine a resonant frequency of the resonator based on the electromagnetic waves reflected by the resonator at different times over a period; and   an analyzer configured to determine a temporal change in strain imparted to the substrate based on a shift in the resonant frequency of the resonator over the period.   
     
     
         18 . The monitoring system of  claim 17 , further including a machine-readable storage medium storing instructions executable by a computer for:
 determining the resonant frequency of the resonator;   determining the shift in the resonant frequency of the resonator based on the received reflected electromagnetic waves at different times over the period in response to electromagnetic probe signals directed toward the strain sensor at different times over the period; and   determining the temporal change in the strain imparted to the substrate based on the shift in resonant frequency of the resonator over the period.   
     
     
         19 . A method of manufacturing a strain sensor, the method comprising the steps of:
 providing a substrate; and   forming a resonator configured as a strain gauge by:
 forming a conductive layer on the substrate in contact therewith; 
 forming a solid dielectric material on the conductive layer in contact therewith as a dielectric capacitor; and 
 forming a conductive coil on the solid dielectric material in contact therewith, 
   wherein the conductive layer, the solid dielectric material, and the conductive coil of the resonator are configured to undergo strain as strain is imparted to the substrate,   wherein the resonator is configured to be inductively powered without an incorporated power supply,   wherein the resonator is configured to reflect electromagnetic waves corresponding to a resonant frequency of the resonator in response to an alternating magnetic or electromagnetic field directed toward the strain sensor, and   wherein the resonant frequency of the resonator shifts in correspondence with the strain imparted to the substrate.