Carbon nanotube temperature and pressure sensors
The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.
1. A temperature sensor comprising:
a sensor element including a plurality of bundles of electrically interconnected carbon nanotubes having a fixed number of junctions between the bundles of electrically interconnected carbon nanotubes, wherein each bundle of the bundles of electrically interconnected carbon nanotubes includes a plurality of substantially parallel carbon nanotubes, wherein current flows between adjacent bundles of the electrically interconnected carbon nanotubes across the junctions;
at least one electrical contact to the sensor element in electrical communication with the plurality of bundles of electrically interconnected carbon nanotubes; and
a power source in connection with the at least one electrical contact providing a substantially constant current to the plurality of bundles of electrically interconnected carbon nanotubes from which voltage can be measured and a resistance determined, wherein the temperature sensor measures temperature independent of pressure by correlating the resistance of the bundles of electrically interconnected carbon nanotubes to temperature through a linear temperature dependent resistivity that is defined by:
ρ( T )=α T+ρ T EXP( T T /( T+T S ),
where ρ is the resistance,
T is the temperature,
α and ρ t are temperature independent constants,
T t is a temperature corresponding to thermal voltage fluctuations that increase energy of electronic states above an activation energy, and
T t /T s is a ratio defining tunneling in the absence of thermal fluctuations.
2. The temperature sensor of claim 1 , wherein the plurality of bundles of electrically interconnected carbon nanotubes is fixed to a rigid substrate.
3. The temperature sensor of claim 1 , wherein the bundles of electrically interconnected carbon nanotubes are carbon nanotubes having a purity of greater than 90%.
4. The temperature sensor of claim 2 , wherein the rigid substrate comprises a glass, plastic, metal, or semiconductor material.
5. The temperature sensor of claim 2 , wherein the rigid substrate has a shear modulus of 1.0 Gpa or greater.
6. The temperature sensor of claim 1 , wherein the bundles of electrically interconnected carbon nanotubes are fixed in a matrix comprising a polymer, a metal, a glass, a ceramic, a semiconductor material or a combination thereof.
7. The temperature sensor of claim 1 , wherein the power source comprises an AC power supply, DC power supply or generated by thermoelectric power.
8. The temperature sensor of claim 1 , wherein the power source comprises an AC power supply and the capacitance of the bundles of electrically interconnected carbon nanotubes is correlated to the temperature or the power source comprises a DC power supply and the resistance of the bundles of electrically interconnected carbon nanotubes is correlated to the temperature.
9. The temperature sensor of claim 1 , wherein the sensor element has a thickness ranging from about 20 nm to about 100 nm.