Piezoelectric transducer

• US 20030006673A1
• Filed: 09/06/2002
• Published: 01/09/2003
• Est. Priority Date: 12/30/1997
• Status: Active Grant

• Current Assignee: Remon Medical Technologies Ltd. (Boston Scientific Corporation)
• Original Assignee: Remon Medical Technologies Ltd. (Boston Scientific Corporation)
• Inventors: Tsaliah, Yoseph, Doron, Eyal, Porat, Yarlv
• Granted Patent: US 6,720,709 B2
• Time in Patent Office: Days
• US Class Current: 310/324
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/413 Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
• CPC Class Codes: A61N 1/37288 Communication to several implantable medical devices within one patient
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/72 Devices for measuring pulsing fluid flows
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A miniature piezoelectric transducer element is provided, comprising: (a) a cell element having a cavity; (b) a flexible piezoelectric layer attached to the cell member, the piezoelectric layer having an external surface and an internal surface, the piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic wave; and (c) a first electrode attached to the external surface and a second electrode attached to the internal surface of the piezoelectric layer. At least one of the electrodes may be specifically shaped so as to provide a maximal electrical output, wherein the electrical output may be current, voltage or power. A preferred shape of the electrodes includes two cores interconnected by a connecting member. The transducer element may function as a transmitter. When used as a transmitter, the electrodes are electrically connected to an electrical circuit including a switching element for modulating the reflected acoustic wave by controllably changing the mechanical impedance of the piezoelectric layer according to the frequency of an electrical message signal arriving from an electronic member, such as a sensor. Third and fourth electrodes may be attached to the piezoelectric layer and the electrical circuit, such that the switching element alternately connects the electrodes in parallel and anti-parallel electrical connections so as to controllably change the mechanical impedance of the piezoelectric layer.

Claims

1. A transducer element, comprising:

(a) a cell member having a cavity;

(b) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic wave; and

(c) a first electrode attached to said external surface and a second electrode attached to said internal surface.

2. The transducer element of claim 1, wherein the wavelength of said acoustic wave is substantially larger than said dimensions.

3. The transducer element of claim 2, wherein said cavity is etched into a substrate.

4. The transducer element of claim 3, where said substrate includes an electrically insulating layer and an electrically conducting layer.

5. The transducer element of claim 4, wherein said first electrode is integrally made with a substantially thin electrically conducting layer disposed on said substrate.

6. The transducer element of claim 5, wherein said substantially thin electrically conducting layer is connected to said substrate by means of a sealing connection.

7. The transducer element of claim 3, wherein said substrate includes a plurality of cell members.

8. The transducer element of claim 7, wherein said plurality of cell members are electrically connected in parallel connections.

9. The transducer element of claim 7, wherein said plurality of cell members are electrically connected in serial connections.

10. The transducer element of claim 1, wherein said cell member is circular in shape.

11. The transducer element of claim 2, wherein said cavity includes a gas.

12. The transducer element of claim 11, wherein said gas is of substantially low pressure.

13. The transducer element of claim 2, wherein said transducer element is used as a transmitter.

14. The transducer element of claim 13, further including a switching element electrically connected thereto so as to controllably change the mechanical impedance of said piezoelectric layer.

16. The transmitter element of claim 15, wherein said cavity is isolated.

17. The transmitter element of claim 15, wherein the switching frequency of said switching element equals the frequency of an electrical message signal arriving from an electric member.

18. The transmitter element of claim 17, wherein said electronic member is a sensor.

19. The transmitter element of claim 15, wherein said switching element is for modulating a reflected acoustic wave according to a message signal arriving from an electronic component.

20. The transmitter element of claim 15, further including a third electrode attached so said external surface and a fourth electrode attached to said internal surface.

21. The transmitter element of claim 20, wherein said switching element alternately connects said electrodes in parallel and anti-parallel connections, thereby controllably changing the mechanical impedance of said piezoelectric layer.

22. The transmitter element of claim 20, wherein said electrodes are electrically interconnected by means of a substantially built-in anti-parallel connection.

23. The transmitter element of claim 20, wherein said electrodes are electrically interconnected by means of a substantially built-in parallel connection.

24. The transmitter element of claim 20, wherein said switching element is an on/off switch.

25. The transmitter element of claim 20, wherein said piezoelectric layer includes first and second portions having opposite polarities.

15. A transmitter element, comprising:

(a) a cell member having a cavity;

(b) a substantially flexible piezoelectric layer attached to said cell member, said piezoelectric layer having an external surface and an internal surface, said piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic field; and

(c) a first electrode attached to said external surface and a second electrode attached to said internal surface, said electrodes coupled to an electrical circuit, said electrical circuit having a switching element, whereby a switching frequency of said switching element controls the mechanical impedance of the piezoelectric layer.