Piezoelectric transducer

1. An implantable medical device, comprising:

an acoustic transducer configured to receive an acoustic interrogation signal; and

a means for modulating a reflected acoustic wave from the acoustic transducer, the reflected acoustic wave including data to be transmitted from the implantable medical device.

2. The implantable medical device of claim 1 , wherein the means for modulating a reflected acoustic wave comprises a switching element coupled to the acoustic transducer.

3. The implantable medical device of claim 2 , wherein the acoustic transducer includes a piezoelectric layer, and wherein the switching element is configured to controllably change the mechanical impedance of the piezoelectric layer based on the data.

4. The implantable medical device, of claim 2 , further comprising a sensor configured for sensing at least one parameter and generating an electrical sensor signal, and wherein the switching element is configured to controllably change the mechanical impedance of the piezoelectric layer based on the frequency of the electrical sensor signal.

5. The implantable medical device of claim 1 , wherein the acoustic transducer is configured to convert the acoustic interrogation signal into an electrical signal for providing electrical power to one or more components of the implantable medical device.

6. The implantable medical device of claim 1 , wherein the acoustic transducer comprises:

a cell member including at least one cavity;

a flexible piezoelectric layer coupled to the cell member, the piezoelectric layer having an external surface and an internal surface; and

a first electrode attached to the external surface of the piezoelectric layer and a second electrode attached to the internal surface of the piezoelectric layer.

7. The implantable medical device of claim 6 , wherein the piezoelectric layer has a resonance at or near a wavelength of the acoustic interrogation signal.

8. The implantable medical device of claim 7 , wherein the piezoelectric layer has a flexibility such that the resonant wavelength is larger than a dimension of the acoustic transducer.

9. The implantable medical device of claim 6 , wherein the piezoelectric layer has a concave shape.

10. The implantable medical device of claim 6 , wherein the cavity includes a gas.

11. The implantable medical device of claim 6 , wherein at least one of the first and second electrodes covers only a portion of a surface of the piezoelectric layer.

12. An implantable medical device, comprising:

at least one sensor configured for sensing at least one parameter of a physiological condition and for generating an electrical sensor signal representative of the physiological condition;

an acoustic transducer coupled to the at least one sensor, the acoustic transducer configured to convert a received acoustic interrogation signal into an electrical signal;

a means for modulating a reflected acoustic wave from the acoustic transducer based on the electrical sensor signal, the reflected acoustic wave including one or more encoded sensor measurements sensed by the at least one sensor.

13. The implantable medical device of claim 12 , wherein the means for modulating a reflected acoustic wave comprises a switching element coupled to the acoustic transducer.

14. The implantable medical device of claim 13 , wherein the acoustic transducer includes a piezoelectric layer, and wherein the switching element is configured to controllably change the mechanical impedance of the piezoelectric layer based on the frequency of the electrical sensor signal.

15. The implantable medical device of claim 12 , wherein the acoustic transducer is configured to convert the acoustic interrogation signal into an electrical signal for providing electrical power to one or more components of the implantable medical device.