Flexible Fingerprint Sensor

• US 20080093687A1
• Filed: 10/23/2007
• Published: 04/24/2008
• Est. Priority Date: 10/23/2006
• Status: Active Grant

• Current Assignee: Patrick R. Antaki
• Original Assignee: Patrick R. Antaki
• Inventors: Antaki, Patrick R.
• Granted Patent: US 8,253,696 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A flexible pressure sensor has a first set of substantially parallel conductors in the x direction, a second set of substantially parallel conductors in the y direction, and a composite material disposed between the first set and second set of conductors. The composite material is capable of returning to substantially its original dimensions on release of pressure. The composite material includes conductive particles at least partially embedded in an elastomeric layer that have no relative orientation and are disposed within the elastomeric layer for electrically connecting the first set and second set of conductors in the z direction under application of sufficient pressure there between.

Claims

1. A flexible pressure sensor comprising:

a composite material comprising a first set of conductive particles, a second set of conductive particles and a third set of conductive particles all of which are at least partially embedded in an elastomeric layer that is capable of returning to substantially its original dimensions on release of pressure;

wherein the first set of conductive particles are electrically connected to form a first set of substantially parallel conductors within a lower portion of the elastomeric layer in the x direction;

wherein the second set of conductive particles are electrically connected to form a second set of substantially parallel conductors within an upper portion of the elastomeric layer in the y direction; and

wherein the third set of conductive particles have no relative orientation and are disposed within the elastomeric layer for electrically connecting the first set and second set of conductors in the z direction under application of sufficient pressure there between.

2. The flexible pressure sensor as recited in claim 1, further comprising:

a first layer disposed above the composite material;

or

a second layer disposed below the composite material.

3. The flexible pressure sensor as recited in claim 2, wherein the first and second layers provide protection against contamination or physical damage, adhesion, a mechanical mounting structure, a flexible substrate or a combination thereof.

4. The flexible pressure sensor as recited in claim 1, wherein the composite material is encapsulated in a protective material having a first set of conductive leads electrically connected to the first set of conductors that extend through the protective material and a second set of conductive leads electrically connected to the second set of conductors that extend through the protective material.

5. The flexible pressure sensor as recited in claim 1, further comprising a fourth set of conductive particles that are electrically connected to form a third set of substantially parallel conductors in the z direction to connect the second set of conductors to a set of conductive leads within or attached to the lower portion of the elastomeric layer.

6. The flexible pressure sensor as recited in claim 1, wherein:

the sensor is a fingerprint sensor;

the conductive particles comprise a metal, a core particle having a conductive coating, carbon nanotubes, carbon nanofibers, conductive fibers, or a combination thereof, the fingerprint sensor has an overall thickness of less than 0.020 inches; and

the first set of conductors and second set of conductors provide a resolution of at least 300 dots per inch.

7. The flexible pressure sensor as recited in claim 1, wherein the sensor is integrated into a hand-held device, a credit card, a debit card, an identification badge, an identification card, an access card or a passport.

8. A flexible pressure sensor comprising:

a first set of substantially parallel conductors in the x direction;

a second set of substantially parallel conductors in the y direction; and

a composite material disposed between the first set and second set of conductors, wherein the composite material is capable of returning to substantially its original dimensions on release of pressure and comprises conductive particles at least partially embedded in an elastomeric layer that have no relative orientation and are disposed within the elastomeric layer for electrically connecting the first set and second set of conductors in the z direction under application of sufficient pressure there between.

9. The flexible pressure sensor as recited in claim 8, wherein:

the sensor is a fingerprint sensor;

the conductive particles comprise a metal, a core particle having a conductive coating, carbon nanotubes, carbon nanofibers, conductive fibers, or a combination thereof,

the fingerprint sensor has an overall thickness of less than 0.020 inches; and

the first set of conductors and second set of conductors provide a resolution of at least 300 dots per inch.

10. The flexible pressure sensor as recited in claim 8, wherein the sensor is integrated into a hand-held device, a credit card, a debit card, an identification badge, an identification card, an access card or a passport.

11. A flexible pressure sensor comprising:

a first set of substantially parallel conductors in the x direction;

a composite material in contact with the first set of conductors, the composite material comprising a first set of conductive particles and a second set of conductive particles all of which are at least partially embedded in an elastomeric layer that is capable of returning to substantially its original dimensions on release of pressure;

wherein the first set of conductive particles are electrically connected to form a second set of substantially parallel conductors within an upper portion of the elastomeric layer in the y direction; and

wherein the second set of conductive particles have no relative orientation and are disposed within the elastomeric layer for electrically connecting the first set and second set of conductors in the z direction under application of sufficient pressure there between.

12. The flexible pressure sensor as recited in claim 11, further comprising one or more additional layer that provide protection against contamination or physical damage, adhesion, a mechanical mounting structure, a flexible substrate or a combination thereof.

13. The flexible pressure sensor as recited in claim 11, wherein the composite material is encapsulated in a protective material having a first set of conductive leads electrically connected to the first set of conductors that extend through the protective material and a second set of conductive leads electrically connected to the second set of conductors that extend through the protective material.

14. The flexible pressure sensor as recited in claim 11, further comprising a fourth set of conductive particles that are electrically connected to form a third set of substantially parallel conductors in the z direction to connect the second set of conductors to a set of conductive leads within or attached to the lower portion of the elastomeric layer.

15. The flexible pressure sensor as recited in claim 11, wherein:

the sensor is a fingerprint sensor;

the conductive particles comprise a metal, a core particle having a conductive coating, carbon nanotubes, carbon nanofibers, conductive fibers, or a combination thereof,

the fingerprint sensor has an overall thickness of less than 0.020 inches; and

the first set of conductors and second set of conductors provide a resolution of at least 300 dots per inch.

16. The flexible pressure sensor as recited in claim 11, wherein the sensor is integrated into a hand-held device, a credit card, a debit card, an identification badge, an identification card, an access card or a passport.

17. A flexible fingerprint sensor comprising:

a first set of substantially parallel conductors in the x direction attached to, deposited on or placed on a flexible substrate;

a composite material in contact with the first set of conductors, the composite material comprising a first set of conductive particles and a second set of conductive particles all of which are at least partially embedded in an elastomeric layer that is capable of returning to substantially its original dimensions on release of pressure;

wherein the first set of conductive particles are electrically connected to form a second set of substantially parallel conductors within an upper portion of the elastomeric layer in the y direction;

wherein the second set of conductive particles have no relative orientation and are disposed within the elastomeric layer for electrically connecting the first set and second set of conductors in the z direction under application of sufficient pressure there between;

wherein the conductive particles comprise a metal, a core particle having a conductive coating, carbon nanotubes, carbon nanofibers, conductive fibers, or a combination thereof,

wherein the fingerprint sensor has an overall thickness of less than 0.020 inches; and

wherein the first set of conductors and second set of conductors provide a resolution of at least 300 dots per inch.

18. The flexible fingerprint sensor as recited in claim 17, further comprising a fourth set of conductive particles that are electrically connected to form a third set of substantially parallel conductors in the z direction to connect the second set of conductors to a set of conductive leads within or attached to the lower portion of the elastomeric layer.

19. A method for fabricating a flexible pressure sensor comprising the steps of:

providing a composite material that is capable of returning to substantially its original dimensions on release of pressure and comprises conductive particles at least partially embedded in an elastomeric layer that have no relative orientation and are disposed within the elastomeric layer for electrically connecting a first set and a second set of conductors in the z direction under application of sufficient pressure there between;

providing the first set of substantially parallel conductors in the x direction below or within a lower portion of the composite material; and

providing the second set of substantially parallel conductors in the y direction above or within an upper portion of the composite material.

20. The method as recited in claim 19, wherein:

the first set of parallel conductors are created by electrically connecting a first set of conductive particles within the lower portion of the elastomeric layer in the x direction;

or

the second set of parallel conductors are created by electrically connecting a second set of conductive particles within the upper portion of the elastomeric layer in the y direction.

21. The method as recited in claim 19, wherein:

the first set of parallel conductors are created by electrically connecting a first set of conductive particles within the lower portion of the elastomeric layer in the x direction;

the second set of parallel conductors are created by electrically connecting a second set of conductive particles within the upper portion of the elastomeric layer in the y direction; and

wherein the first and second set of parallel conductors are semi-conductive or partially conductive.

22. The method as recited in claim 19, further comprising the step of creating a third set of substantially parallel conductors in the z direction by electrically connecting a fourth set of conductive particles that are electrically between the second set of conductors and a set of conductive leads within or attached to the lower portion of the elastomeric layer.

23. The method as recited in claim 19, wherein:

the first set of parallel conductors are attached to, deposited on or placed on a first flexible substrate;

or

the second set of parallel conductors are attached to, deposited on or placed on a second flexible substrate.

24. The method as recited in claim 19, wherein:

the sensor is a fingerprint sensor;

the conductive particles comprise a metal, a core particle having a conductive coating, carbon nanotubes, carbon nanofibers, conductive fibers, or a combination thereof,

the fingerprint sensor has an overall thickness of less than 0.020 inches; and

the first set of conductors and second set of conductors provide a resolution of at least 300 dots per inch.

25. The method as recited in claim 19, further comprising the steps of:

attaching conductive leads to the first set of conductors and the second set of conductors;

providing one or more additional layers;

encapsulating the sensor in a package;

or

integrating the sensor into a hand-held device, a credit card, a debit card, an identification badge, an identification card, an access card or a passport.