Switchable RFID antennas responsive to an environmental sensor

1. A sensor system comprising:

a RFID tag having an antenna and an integrated circuit electrically coupled to the antenna;

a plurality of sensor devices electrically coupled to the integrated circuit; and

a plurality of electrical connections between the integrated circuit and the plurality of sensor devices,

wherein the integrated circuit is configured to sense whether each of the plurality of sensor devices is in a conductive state or in a non-conductive state, and produce a different output based on the state of each of the plurality of sensor devices,

wherein the output is adapted to be transmitted through the antenna to a reader,

wherein an at least one of the plurality of sensor devices comprises a dopant layer, a conductive polymer, and a permeable membrane located between the dopant layer and the conductive polymer,

wherein when the at least one of the plurality of sensor devices reaches a threshold temperature, the dopant layer diffuses through the permeable membrane into the conductive polymer to increase conductivity of the conductive polymer, and

wherein at least one of the electrical connections is electrically connected to the conductive polymer.

2. The sensor system of claim 1 , wherein the dopant layer comprises a water-based acrylic adhesive layer containing a microencapsulated dopant.

3. The sensor system of claim 1 , wherein the at least one of the electrical connections comprises at least two electrical terminals.

4. The sensor system of claim 1 , wherein the RFID tag comprises a passive tag.

5. A sensor system comprising:

a RFID tag having an antenna and an integrated circuit electrically coupled to the antenna;

a plurality of sensor devices electrically coupled to the integrated circuit; and

a plurality of electrical connections between the integrated circuit and the plurality of sensor devices,

wherein the integrated circuit is configured to sense whether each of the plurality of sensor devices is in a conductive state or in a non-conductive state, and produce a different output based on the state of each of the plurality of sensor devices,

wherein the output is adapted to be transmitted through the antenna to a reader,

wherein an at least one of the plurality of sensor devices comprises a chemical etchant layer, a conductive metal layer, and a permeable membrane located between the chemical etchant layer and the conductive metal layer, and

wherein when the at least one of the plurality of sensor devices reaches a threshold temperature, the chemical etchant layer diffuses through the membrane into the conductive metal layer to degrade conductivity of the conductive metal layer.

6. The sensor system of claim 5 , wherein at least one of the electrical connections is electrically connected to the conductive metal layer.

7. The sensor system of claim 5 , wherein the chemical etchant layer comprises a water-based acrylic adhesive layer containing a microencapsulated etchant.

8. The sensor system of claim 5 , wherein at least one of the electrical connections comprises at least two electrical terminals.

9. The sensor system of claim 5 , wherein the RFID tag comprises a passive tag.

10. A sensor system comprising:

a RFID tag having an antenna and an integrated circuit electrically coupled to the antenna;

a plurality of sensor devices electrically coupled to the integrated circuit; and

a plurality of electrical connections between the integrated circuit and the plurality of sensor devices,

wherein the integrated circuit is configured to sense whether each of the plurality of sensor devices is in a conductive state or in a non-conductive state, and produce a different output based on the state of each of the plurality of sensor devices,

wherein the output is adapted to be transmitted through the antenna to a reader,

wherein an at least one of the plurality of sensor devices comprises a first chamber with a conductive liquid, a second chamber, and a permeable membrane located between the first chamber and the second chamber, and

wherein when the at least one of the plurality of sensor devices reaches a threshold temperature, the conductive liquid diffuses through the membrane into the second chamber, thereby causing a change in conductivity of the at least one of the plurality of sensor devices.

11. The sensor system of claim 10 , wherein at least one of the electrical connections is electrically connected to the first chamber.

12. The sensor system of claim 10 , wherein at least one of the electrical connections is electrically connected to the second chamber.

13. The sensor system of claim 10 , wherein at least one of the electrical connections comprises at least two electrical terminals.

14. The sensor system of claim 10 , wherein the RFID tag comprises a passive tag.

15. A sensor system comprising:

a RFID tag having an antenna and an integrated circuit electrically coupled to the antenna;

a plurality of sensor devices electrically coupled to the integrated circuit; and

a plurality of electrical connections between the integrated circuit and the plurality of sensor devices,

wherein the integrated circuit is configured to sense whether each of the plurality of sensor devices is in a conductive state or in a non-conductive state, and produce a different output based on the state of each of the plurality of sensor devices,

wherein the output is adapted to be transmitted through the antenna to a reader,

wherein an at least one of the plurality of sensor devices comprises a first chamber with a gel, a second chamber, and a permeable membrane located between the first chamber and the second chamber, and

wherein when the at least one of the plurality of sensor devices reaches a threshold temperature, the gel passes through the permeable membrane in to the second chamber, thereby causing a change in conductivity of the at least one of the plurality of sensor devices.

16. The sensor system of claim 15 , wherein at least one of the electrical connections is electrically connected to the first chamber.

17. The sensor system of claim 15 , wherein at least one of the electrical connections is electrically connected to the second chamber.

18. The sensor system of claim 15 , wherein at least one of the electrical connections comprises at least two electrical terminals.

19. The sensor system of claim 15 , wherein the RFID tag comprises a passive tag.

20. A sensor system comprising:

a RFID tag having an antenna and an integrated circuit electrically coupled to the antenna;

a plurality of sensor devices electrically coupled to the integrated circuit; and

a plurality of electrical connections between the integrated circuit and the plurality of sensor devices,

wherein the integrated circuit is configured to sense whether each of the plurality of sensor devices is in a conductive state or in a non-conductive state, and produce a different output based on the state of each of the plurality of sensor devices,

wherein the output is adapted to be transmitted through the antenna to a reader,

wherein an at least one of the plurality of sensor devices comprises a first chamber with a pH modifying liquid, a second chamber with a pH sensitive gel, a third chamber, a first membrane located between the first chamber and the second chamber, and a second membrane located between the second chamber and the third chamber, and

wherein when the at least one of the plurality of sensor devices reaches a threshold temperature, the pH modifying liquid diffuses through the first membrane into the second chamber and turns the pH sensitive gel to liquid, causing the pH sensitive gel to pass through the second membrane, thereby causing a change in conductivity of the at least one of the plurality of sensor devices.

21. The sensor system of claim 20 , wherein at least one of the electrical connections is electrically connected to the third chamber.

22. The sensor system of claim 20 , wherein at least one of the electrical connections comprises at least two electrical terminals.

23. The sensor system of claim 20 , wherein the RFID tag comprises a passive tag.