Accelerometer based on the measurement of Casimir force fluctuations
View Patent ↗An accelerometer based on the measurement of Casimir force fluctuations is described. The accelerometer comprises a sealed housing containing a vacuum or a liquid, a piezoelectric plate fixed with the sealed housing, and a mass moveable within the sealed housing located in proximity to the piezoelectric plate. The moveable mass and the piezoelectric plate each have conductive surfaces which are located from each other at a distance which creates a Casimir Effect between the movable mass and the piezoelectric plate. Fluctuations in acceleration of the moveable mass cause fluctuations in the Casimir force on the piezoelectric plate. The acceleration fluctuations cause fluctuations in an electric output of the piezoelectric plate. The fluctuations in electric output are measured and used to calculate an acceleration and direction of movement of the accelerometer or a host device in which the accelerometer is carried.
1. An accelerometer, comprising:
a sealed housing having an interior surface which defines a cavity;
a piezoelectric sensor located within the sealed housing, the piezoelectric sensor comprising a piezoelectric plate rigidly attached to the interior surface of the sealed housing and having a conductive surface having a first dielectric permittivity;
a first mass located within the sealed housing and having a conductive surface having a second dielectric permittivity, the first mass being attached to the interior surface of the sealed housing in proximity to the conductive surface of the piezoelectric plate to produce a Casimir effect between the conductive surface of the first mass and the conductive surface of the piezoelectric plate which causes a proportional force to be exerted on the piezoelectric plate when the first mass accelerates;
voltage detection circuitry connected to opposite sides of the piezoelectric plate which detects and measures electrical output of the piezoelectric plate in terms of a voltage generated by forces exerted on the piezoelectric plate.
2. The accelerometer of claim 1 , wherein the first mass is attached to the interior surface of the sealed housing by a cantilever arm.
3. The accelerometer of claim 2 , wherein the piezoelectric plate is attached to the interior surface of the sealed housing by two or more anchor rigid arms and wherein the anchoring arms are shorter than the cantilever arm.
4. The accelerometer of claim 3 , wherein the anchoring arms are at least three times shorter than the cantilever arm.
5. The accelerometer of claim 4 , wherein the piezoelectric material is lead zirconate titanate (PZT).
6. The accelerometer of claim 1 , wherein the first dielectric permittivity and second dielectric permittivity are the same.
7. The accelerometer of claim 6 , wherein the cavity comprises a vacuum.
8. The accelerometer of claim 6 , wherein the conductive surface of the first mass and the conductive surface of the piezoelectric sensor comprises a gold-plating.
9. The accelerometer of claim 8 , wherein the gold-plating has a thickness of approximately 2000 Ångströms.
10. The accelerometer of claim 1 , wherein the first dielectric permittivity and second dielectric permittivity are different.
11. The accelerometer of claim 10 , wherein the cavity comprises an immersion liquid, wherein the immersion liquid is a chemically inert liquid which is selected to have a dielectric permittivity which is higher than the first dielectric permittivity of the conductive surface of the piezoelectric plate and lower than the second dielectric permittivity of the conductive surface of the mass.
12. The accelerometer of claim 11 , wherein the immersion liquid is one of bromobenzene, ethanol or p-Xylene.
13. The accelerometer of claim 1 , wherein the conductive surface of the first mass comprises a gold-plating and the conductive surface of the piezoelectric sensor a silica-plating.
14. The accelerometer of claim 13 , wherein the cavity comprises an immersion liquid, wherein the immersion liquid is a chemically inert liquid which is selected to have a dielectric permittivity which is lower than the gold-plating of the mass and higher than the silica-plating of the piezoelectric plate.
15. The accelerometer of claim 14 , wherein the immersion liquid is one of bromobenzene, ethanol or p-Xylene.
16. The accelerometer of claim 1 , comprising a first pair of piezoelectric sensors rigidly attached to the interior surface of the sealed housing, each of the piezoelectric sensors in the first pair of piezoelectric sensors including a piezoelectric plate having a conductive surface having the first dielectric permittivity, the conductive surfaces of the piezoelectric plates in the first pair of piezoelectric sensors being located on opposite sides of the first mass so as to face a conductive surface on the first mass, the conductive surfaces of the piezoelectric plates in the first pair of piezoelectric sensors being aligned in parallel so to form a first axis, the first pair of piezoelectric sensors measuring acceleration in opposite directions along the first axis defined by the parallel piezoelectric plates of the first pair of piezoelectric sensors;
wherein the first mass is in proximity to the conductive surfaces of the first pair of piezoelectric sensors to produce a Casimir effect between the conductive surface of the first mass and the conductive surfaces of the first pair of piezoelectric sensors which causes a proportional force to be exerted on the piezoelectric plates of the first pair of piezoelectric sensors when the first mass accelerates.
17. The accelerometer of claim 16 , further comprising a second pair of piezoelectric sensors rigidly attached to the interior surface of the sealed housing oriented orthogonal to the first pair of piezoelectric sensors, each of the piezoelectric sensors in the second pair of piezoelectric sensors including a piezoelectric plate having a conductive surface having the first dielectric permittivity, the conductive surfaces of the piezoelectric plates in the second pair of piezoelectric sensors being located on opposite sides of the first mass so as to face a conductive surface on the first mass, the conductive surfaces of the piezoelectric plates in the second pair of piezoelectric sensors being aligned in parallel so to form a second axis orthogonal to the first axis, the second pair of piezoelectric sensors measuring acceleration in opposite directions along the first axis defined by the parallel conductive surfaces of the second pair of piezoelectric sensors;
wherein the first mass is in proximity to the conductive surfaces of the second pair of piezoelectric sensors to produce a Casimir effect between the conductive surface of the first mass and the conductive surfaces of the second pair of piezoelectric sensors which causes a proportional force to be exerted on the piezoelectric plates of the second pair of piezoelectric sensors when the first mass accelerates.
18. The accelerometer of claim 17 , further comprising:
a second mass located within the sealed housing and having a conductive surface having the second dielectric permittivity, the second mass being attached to the interior surface of the sealed housing; and
a third pair of piezoelectric sensors rigidly attached to the interior surface of the sealed housing oriented orthogonal to the first pair and second of piezoelectric sensors, each of the piezoelectric sensors in the third pair of piezoelectric sensors including a piezoelectric plate having a conductive surface having the first dielectric permittivity, the conductive surfaces of the piezoelectric plates in the third pair of piezoelectric sensors being located on opposite sides of the second mass so as to face a conductive surface on the second mass, the conductive surfaces of the piezoelectric plates in the third pair of piezoelectric sensors being aligned in parallel so to form a third axis orthogonal to the first axis and second axis, the third pair of piezoelectric sensors measuring acceleration in opposite directions along the third axis defined by the parallel conductive surfaces of the third pair of piezoelectric sensor;
wherein the second mass is in proximity to the conductive surfaces of the third pair of piezoelectric sensors to produce a Casimir effect between the conductive surface of the second mass and the conductive surfaces of the third pair of piezoelectric sensors which causes a proportional force to be exerted on the piezoelectric plates of the third pair of piezoelectric sensors when the second mass accelerates.
19. The accelerometer of claim 1 , further comprising an amplifier configured to amplify the electrical output received from the piezoelectric plate.
20. The accelerometer of claim 1 , further comprising a processor configured to calculating acceleration based on electrical output from the one piezoelectric plate.
21. The accelerometer of claim 1 , wherein the piezoelectric plate operates in transverse mode and electrical contacts for the voltage detection circuitry are connected to the piezoelectric plate at opposite sides of the piezoelectric plate, perpendicular to the conductive surface of the piezoelectric plate.
22. The accelerometer of claim 1 , wherein the first mass is a cuboid.
23. The accelerometer of claim 1 , wherein the first mass is a cylinder and the piezoelectric plate is oriented parallel to a longitudinal axis of the cylinder.
24. A portable electronic device, comprising:
a processor;
an accelerometer connected to the processor, the accelerometer including:
a sealed housing having an interior surface which defines a cavity;
a piezoelectric sensor located within the sealed housing, the piezoelectric sensor comprising a piezoelectric plate rigidly attached to the interior surface of the sealed housing and having a conductive surface having a first dielectric permittivity; a first mass located within the sealed housing and having a conductive surface having a second dielectric permittivity, the first mass being attached to the interior surface of the sealed housing in proximity to the conductive surface of the piezoelectric plate to produce a Casimir effect between the conductive surface of the first mass and the conductive surface of the piezoelectric plate which causes a proportional force to be exerted on the piezoelectric plate when the first mass accelerates; and
voltage detection circuitry connected to opposite sides of the piezoelectric plate which detects and measures electrical output of the piezoelectric plate in terms of a voltage generated by forces exerted on the piezoelectric plate;
wherein the processor is configured for receiving electrical output from the voltage detection circuitry.
25. The portable electronic device of claim 24 , wherein the cavity comprises an immersion liquid, wherein the immersion liquid is a chemically inert liquid which is selected to have a dielectric permittivity which is higher than the first dielectric permittivity of the conductive surface of the piezoelectric plate and lower than the second dielectric permittivity of the conductive surface of the mass.
26. An accelerometer, comprising:
a sealed housing having an interior surface which defines a cavity;
a piezoelectric sensor located within the sealed housing, the piezoelectric sensor comprising a piezoelectric plate rigidly attached to the interior surface of the sealed housing and having a conductive surface having a first dielectric permittivity;
a first mass located within the sealed housing and having a conductive surface having a second dielectric permittivity, the first mass being attached to the interior surface of the sealed housing in proximity to the conductive surface of the piezoelectric plate to produce a Casimir effect between the conductive surface of the first mass and the conductive surface of the piezoelectric plate which causes a proportional force to be exerted on the piezoelectric plate when the first mass accelerates;
wherein the cavity comprises an immersion liquid, wherein the immersion liquid is a chemically inert liquid which is selected to have a dielectric permittivity which is higher than the first dielectric permittivity of the conductive surface of the piezoelectric plate and lower than the second dielectric permittivity of the conductive surface of the mass.