RFID tag including environmentally sensitive materials

1. An RFID device, comprising: a substrate; an antenna structure having a first sheet of electrically conductive material including two parts and an elongated slot extending therebetween, the elongated slot having a length and one open end; a wireless communications device coupled to the substrate; and a non-ambient environmentally responsive material deposited within or across a portion of the elongated slot wherein the material alters the level of interaction between the two parts of the antenna structure in response to a change in an environmental factor and wherein the interaction between the two parts of the antenna varies along a length of the slot.

2. The RFID device of claim 1 , wherein the antenna structure is a slot-loop antenna.

3. The RFID device of claim 1 , wherein the two parts include a plurality of interdigitated fingers along a portion of the elongated slot.

4. The RFID device of claim 3 , wherein the environmentally responsive material is disposed proximate to the interdigitated fingers.

5. The RFID device of claim 1 , further comprising a second sheet of electrically conductive material disposed on an exposed side of the environmentally-responsive material.

6. The RFID device of claim 1 , wherein the environmentally-responsive material is disposed over the antenna structure as a coating.

7. The RFID device of claim 1 , wherein

the sheet of electrically conductive material having a first part and a second part, the first and second parts being coupled together reactively, conductively or a combination of both reactive and conductive coupling, such that an operating parameter of the antenna structure varies in relation to an environmental condition to alter the gain, far field performance and near field performance of the RFID device.

8. The RFID device of claim 7 , wherein the coupling is facilitated by a dielectric material.

9. The RFID device of claim 8 , wherein the dielectric material is responsive to the environmental condition.

10. The RFID device of claim 8 , wherein the dielectric material is disposed between the first part and the second part.

11. An RFID device, comprising: a substrate; an antenna structure having a sheet of electrically conductive material having a first part and a second part, the two parts being capacitively coupled together such that an operating parameter of the antenna structure varies in relation to an environmental condition wherein an elongated slot having a length that extends between the two parts and a non-ambient environmentally responsive material is desposited within a portion of the length of the elongated slot and the non-ambient environmentally responsive material alters the level of interaction between the two parts of the antenna structure in response to an environmental and wherein the interaction between the two parts of the antenna varies along a length of the slot; and a wireless communications device coupled to the antenna structure.

12. A method of forming an RFID device, comprising:

depositing a first electrically conductive material on a substrate; defining an elongated slot in the first electrically conductive material such that the conductive material includes two parts the elongated slot having a length and an end; depositing a non-ambient environmentally responsive material at a location along the elongated slot wherein the material alters the level of interaction between the two parts in response to an environmental factor selected from the group including temperature, physical compression, bending, stretching air pressure, biological or chemical and wherein the interaction between the two parts of the antenna varies along a length of the slot; and coupling a wireless communications device to the antenna structure.

13. The method of claim 12 , further comprising:

defining an interdigitated region at a location along the elongated slot; and

depositing an environmentally responsive material at the interdigitated region.

14. The method of claim 12 , further comprising depositing a second electrically conductive material on an exposed side of the environmentally-responsive material.

15. The method of claim 12 , further comprising coating the first electrically conductive material with an environmentally responsive material.

16. The method of claim 12 , wherein the-sheet of electrically conductive material has a first part and a second part; and the two parts are

capacitively coupled.

17. The method of claim 12 , wherein the environmentally-responsive material is a dielectric.

18. The method of claim 12 , wherein the antenna structure is a slot-loop antenna.

19. The method of claim 12 , wherein the environmentally-responsive material is disposed within the elongated slot.