Thin flexible sensor

• US 8,994,528 B2
• Filed: 06/13/2008
• Issued: 03/31/2015
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Celik-Butler, Zeynep, Butler, Donald P.
• Primary Examiner(s): Mehmood, Jennifer
• Assistant Examiner(s): Terrell, Emily C
• Application Number:
  US12/664,838
• Publication Number:
  US 20100245114A1
• Time in Patent Office: 2,482 Days
• Field of Search: 340/239.22, 340/539.26, 340/573.1, 340/572.1
• US Class Current: 340/539.22
• CPC Class Codes: G01D 11/245 Housings for sensors
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: Y10T 156/1075 of plural laminae from single stock and assembling to each other or to additional lamina

Abstract

The present invention provides a sensor (100, 300, 400) that includes a thin and substantially flat flexible substrate (102, 406) having one or more sensor arrays (104, 302), a power source (106, 416), an output interface (108, 418) and a processor or analog circuit (304), all of which are disposed on the substantially flat flexible substrate (102, 406). The substrate (102, 406) can be any shape (e.g., rectangular, circular, a polygon, an irregular shape that is decorative) and made from a polymer, metal film or other suitable material. Note that the substrate can be rigid or semi-flexible instead of flexible. A protective layer may cover the sensor array (104, 302), the power source (106, 416), and the processor or analog circuit (304). Alternatively, a protective covering can be used to encapsulate the device. The one or more sensor arrays (104, 302) measure acceleration, force or pressure.

Claims

1. A sensor (100, 300, 400) comprising:

a thin and substantially flat flexible substrate (102, 406);

one or more sensor arrays (104, 302) fabricated on the flexible substrate (102, 406) that measure acceleration, force or pressure, wherein each sensor array includes at least a pressure sensor comprising a bridge structure having a central plate suspended over a pit by at least two bridge arms and one or more piezoresistors disposed on at least one of the bridge arms;

an output interface (108, 418) disposed on the flexible substrate (102, 406);

a processor or an analog circuit (304) disposed on the flexible substrate (102, 406) and connected to the one or more sensor arrays (104, 302) and the output interface (108, 418);

a power source (106, 416) disposed on the flexible substrate (102, 406) and connected to the one or more sensor arrays (104, 302), the output interface (108, 418), and the processor or the analog circuit (304); and

the flexible substrate (102, 406), the one or more sensor arrays (104, 302), the output interface (108, 418), the processor or an analog circuit (304) and the power source (106, 416) form a flexible integrated circuit that can be stretched, wrinkled or flexed without degradation of the flexible integrated circuit.

2. The sensor (100, 300, 400) as recited in claim 1, wherein:

the flexible substrate (102, 406) comprises a polymer or a metal film; and

the one or more sensor arrays (104, 302) measure depth, force, frequency or acceleration of compressions.

3. The sensor (100, 300, 400) as recited in claim 1, further comprising a protective layer covering the sensor array(s) (104, 302), the processor or the analog circuit (304), and the output interface (108, 418).

4. The sensor (100, 300, 400) as recited in claim 1, wherein the sensor array(s) (104, 302) comprise:

one or more accelerometers (200); and

one or more pressure sensors (202) positioned around the accelerometer(s) (200).

5. The sensor (100, 300, 400) as recited in claim 1, wherein:

the processor or the analog circuit (304) determines whether one or more operational parameters are within one or more guidelines and provides a feedback regarding whether the operational parameters are within the guidelines via the output interface (108, 418); and

the one or more operational parameters comprise an applied pressure, an acceleration, a shearing force, a compressive force or a combination thereof.

6. The sensor (100, 300, 400) as recited in claim 5, further comprising a data storage (310) connected to the processor or the analog circuit (304) that stores the one or more parameters, the feedback, a status of the sensor, diagnostic information or a combination thereof.

7. The sensor (100, 300, 400) as recited in claim 6, wherein the data storage (310) comprises a RFID tag, a magnetic strip, a memory or a combination thereof.

8. The sensor (100, 300, 400) as recited in claim 1, wherein the substrate (102, 406) is rigid or semi-flexible instead of flexible.

9. The sensor (100, 300, 400) as recited in claim 1, wherein the sensor array(s) (104, 302) further measure one or more operational parameters.

10. The sensor (100, 300, 400) as recited in claim 9, wherein the one or more operational parameters comprise a physical contact with an object or a recipient, a temperature of the object or the recipient, an electrical activity of the object or the recipient, or a combination thereof.

11. The sensor (100, 300, 400) as recited in claim 10, wherein:

the recipient is a human or an animal; and

the object is a machine, a structure, a composition, a vehicle, a plant or a natural object.

12. The sensor (100, 300, 400) as recited in claim 1, wherein the output interface (108, 418) comprises a visual display, a speaker, a multi-tone generator, a communications interface (306) or a combination thereof.

13. The sensor (100, 300, 400) as recited in claim 12, wherein the visual display comprises a set of light emitting diodes, a liquid crystal display or combination thereof that provide a feedback to a user.

14. The sensor (100, 300, 400) as recited in claim 12, wherein the communications interface (306) comprises an optical communications interface, an infrared communications interface, a wireless communications transceiver, a physical communications port or a combination thereof.

15. The sensor (100, 300, 400) as recited in claim 14, wherein the wireless transceiver comprises an active radio frequency identification tag, a passive radio frequency identification tag, a cellular phone, an Internet connection or a personal data assistant.

16. The sensor (100, 300, 400) as recited in claim 1, further comprising:

a geographic locator (208) that is disposed on the flexible substrate (102, 406) and connected to the processor or the analog circuit (304); and

a communications interface (306) disposed on the flexible substrate (102, 406), connected to the processor or the analog circuit (304), wherein the processor or the analog circuit (304) periodically transmits a status of the sensor, a location of the sensor as determined by the geographic locator (208), diagnostic information, a status of the recipient or object, or a combination thereof to another location via the communications interface (306).

17. The sensor (100, 300, 400) as recited in claim 1, wherein the sensor (100, 300, 400) is integrated in or attached to a recipient, an object, a device, a personal item, a clothing or a thin portable user device.

18. The sensor (100, 300, 400) as recited in claim 17, wherein the device comprises a phone, a mobile communications device, a cellular phone, an audio and/or video device or a personal data assistant.

19. The sensor (100, 300, 400) as recited in claim 1, wherein the power source (106, 416) comprises a battery, a solar panel, a layer of piezoelectric film (408) for voltage generation, an electromagnetic voltage generator, an energy harvesting device or a combination thereof.

20. The sensor (100, 300, 400) as recited in claim 19, wherein the battery is replaceable or rechargeable.

21. The sensor (100, 300, 400) as recited in claim 1, wherein the power source (106, 416) comprises:

a battery;

layer of piezoelectric film (408) or other energy harvesting methods for voltage generation; and

a power controller to manage power consumption and storage in the battery and the layer of piezoelectric film.

22. The sensor (100, 300, 400) as recited in claim 1, further comprising a magnetic strip, a RFID tag, a wireless communications device or other information bearing device disposed on the exterior or interior of the sensor.

38. The sensor as recited in claim 1, wherein the sensor has a thickness less than or equal to 1.25 mm.

41. The sensor as recited in claim 1, wherein the central shuttle plate comprises Si₃N₄ and the pit comprises an undercut etched pit.

23. A sensor (100, 300, 400) comprising:

an upper protective layer (402);

a lower protective layer (404); and

a thin and substantially flat flexible polymer or thin metal substrate (102, 406) disposed between the upper protective layer (402) and the lower protective layer (404);

one or more sensor arrays (104, 302) fabricated on the substrate that measure acceleration, force or pressure, wherein each sensor array includes at least a pressure sensor comprising a bridge structure having a central plate suspended over a pit by at least two bridge arms and one or more piezoresistors disposed on at least one of the bridge arms;

an output interface (108, 418) disposed on the substrate (102, 406);

a processor or an analog circuit (304) disposed on the substrate (102, 406) and connected to the sensor array(s) (104, 302) and the output interface (108, 418);

a power source (106, 416) disposed on the substrate (102, 406) and connected to the processor or the analog circuit (304); and

the upper protective layer (402), the lower protective layer (404), the flexible substrate (102, 406), the one or more sensor arrays (104, 302), the output interface (108, 418), the processor or an analog circuit (304) and the power source (106, 416) form a flexible integrated circuit that can be stretched, wrinkled or flexed without degradation of the flexible integrated circuit.

24. The sensor (100, 300, 400) as recited in claim 23, wherein the upper protective layer (402) and the lower protective layer (404) encapsulate the substrate (102, 406).

25. The sensor (100, 300, 400) as recited in claim 23, further comprising an energy producing layer (408) disposed between the lower protective layer (404) and the substrate (102, 406).

26. The sensor (100, 300, 400) as recited in claim 23, wherein the sensor array(s) (104, 302) comprise:

one or more accelerometers (200) ; and

one or more pressure sensors (202) positioned around the accelerometer(s) (200).

27. The sensor (100, 300, 400) as recited in claim 23, wherein:

the processor or the analog circuit (304) determines whether one or more operational parameters are within one or more guidelines and provides a feedback regarding whether the operational parameters are within the guidelines via the output interface (108, 418); and

the one or more operational parameters comprise an applied pressure, an acceleration, a shearing force, a compressive force or a combination thereof.

28. The sensor (100, 300, 400) as recited in claim 23, wherein the substrate (102, 406) is rigid or semi-flexible instead of flexible.

29. The sensor (100, 300, 400) as recited in claim 23, wherein the output interface (108, 418) comprises a visual display, a speaker, a multi-tone generator, a communications interface or a combination thereof.

30. The sensor (100, 300, 400) as recited in claim 24, further comprising:

a geographic locator (208) that is disposed on the flexible substrate (102, 406) and connected to the processor or the analog circuit (304); and

a communications interface (306) disposed on the flexible substrate (102, 406), connected to the processor or the analog circuit (304), wherein the processor or the analog circuit (304) periodically transmits a status of the sensor, a location of the sensor as determined by the geographic locator (208), diagnostic information, a status of a recipient or object, or a combination thereof to another location via the communications interface (306).

31. The sensor (100, 300, 400) as recited in claim 23, wherein the power source (106, 416) comprises a battery, a solar panel, a layer of piezoelectric film (408) for voltage generation, an electromagnetic voltage generator, an energy harvesting device or a combination thereof.

39. The sensor as recited in claim 23, wherein the sensor has a thickness less than or equal to 1.25 mm.

42. The sensor as recited in claim 23, wherein the central shuttle plate comprises Si₃N₄ and the pit comprises an undercut etched pit.

32. A method or manufacturing a sensor comprising the steps of:

passivating a silicon wafer;

adding a polyimide layer to the wafer;

creating one or more sensor arrays (104, 302) on the polyimide layer using a Micro-Electro-Mechanical Systems (MEMS) process wherein the sensor array(s) (104, 302) measure acceleration, force or pressure, wherein each sensor array includes at least a pressure sensor comprising a bridge structure having a central plate suspended over a pit by at least two bridge arms and one or more piezoresistors disposed on at least one of the bridge arms;

dicing the wafer to extract the individual dies/sensors;

printing a circuit on a flexible substrate (102, 406);

applying a paste or epoxy to the flexible substrate (102, 406) to receive and secure the individual dies/sensors;

placing the individual dies/sensors on the flexible substrate (102, 406);

placing the flexible substrate (102, 406) on a lower protective layer (404) containing electrical interconnects and an output interface (108, 418) a processor or an analog circuit (304), and a power source (106, 416);

securing the flexible substrate (102, 406) to the lower protective layer (404);

placing and securing a upper protective layer (402) to the flexible substrate (102, 406) and the lower protective layer (404) to complete assembly of the sensor; and

wherein the foregoing steps form a flexible integrated circuit that can be stretched, wrinkled or flexed without degradation of the flexible integrated circuit.

33. The method as recited in claim 32, further comprising the step of testing the sensor (100, 300, 400).

34. The method as recited in claim 32, wherein the one or more sensor arrays (104, 302) comprises a pressure sensor and the step of creating the one or more sensor arrays (104, 302) on the polyimide layer comprises the steps of:

depositing a layer of Si₃N₄ on top of the polyimide layer;

patterning the layer of Si₃N₄ using a mask to from the bridge structure;

depositing a polysilicon layer on top of the layer of Si₃N₄;

patterning the polysilicon layer using a mask to form the one or more piezoresistors;

depositing a metallic layer on top of the polysilicon layer; and

patterning the metallic layer to form conductive leads for the pressure sensor.

35. The method as recited in claim 32, wherein the polyimide layer comprises a first polyimide layer, and the step of creating the one or more sensor arrays (104, 302) on the first polyimide layer comprises the steps of:

depositing a first layer of Si₃N₄ on top of the first polyimide layer;

depositing a second layer of polyimide on the layer Si₃N₄;

depositing a second layer of Si₃N₄ on top of the second polyimide layer;

patterning the second layer of Si₃N₄ using a mask to from the bridge structure;

depositing a polysilicon layer on top of the layer of Si₃N₄;

patterning the polysilicon layer using a mask to form the one or more piezoresistors;

depositing a metallic layer on top of the polysilicon layer;

patterning the metallic layer to form conductive leads for the pressure sensor; and

underetching the second polyimide layer.

36. The method as recited in claim 32, wherein the one or more sensor arrays (104, 302) further includes an accelerometer, the polyimide layer comprises a first polyimide layer, and the step of creating the one or more sensor arrays (104, 302) on the first polyimide layer comprises the steps of:

depositing a first layer of Si₃N₄ on top of the first polyimide layer;

depositing a metallic layer on top of the first layer of Si₃N₄;

patterning the metallic layer to form conductive leads for the accelerometer;

depositing a second layer of polyimide on the patterned metallic layer;

patterning the second layer of polyimide using a first mask to from one or more anchors;

depositing a second layer of Si₃N₄ on top of the second polyimide layer;

patterning the second layer of Si₃N₄ using a second mask to form the accelerometer; and

underetching the second polyimide layer.

37. The method as recited in claim 32, further comprising wherein the one or more sensor arrays (104, 302) further includes an accelerometer, the polyimide layer comprises a first polyimide layer, and the step of creating the one or more sensor arrays (104, 302) on the first polyimide layer comprises the steps of:

depositing a first layer of Si₃N₄ on top of the first polyimide layer;

depositing a metallic layer on top of the first layer of Si₃N₄;

patterning the metallic layer to form conductive leads for the accelerometer;

depositing a second layer of polyimide on the patterned metallic layer;

patterning the second layer of polyimide using a first mask to from one or more anchors;

depositing a second layer of Si₃N₄ on top of the second polyimide layer;

patterning the second layer of Si₃N₄ using a second mask to form the accelerometer;

depositing a third layer of polyimide on the patterned second layer of Si₃N₄;

patterning the third layer of polyimide using a third mask;

depositing an encapsulant material on the patterned third layer of polyimide;

patterning the encapsulant material using a fourth mask; and

underetching the second polyimide layer and the third polyimide layer.

40. The method as recited in claim 32, wherein the sensor has a thickness less than or equal to 1.25 mm.