Flexible radio frequency identification tags

Abstract

Flexible, stretchable RFID tags are formed by a pocket that is formed from one or more substrates and layers of adhesive, and an electronic circuit that is located within this pocket. The RFID tags can include a stretchable substrate and an electronic circuit attached to the stretchable substrate by one or a finite number of discrete spaced apart attachment locations. When the pocket is formed by relatively thick adhesive layers adhering together one or more flexible substrates to form an internal cavity, the electronic circuit is located within this cavity and either is not adhered to any of the substrates of the cavity, and is free to move about within the cavity, or the electronic circuit can be attached to a substrate by a thin layer of adhesive.

What is claimed is: 
     
         1 . A stretchable radio frequency identification tag comprising:
 a flexible stretchable first substrate;   a flexible stretchable third substrate substantially coextensive with and attached to the first substrate along a periphery of the first and third substrates, the first and third substrates defining an air gap therebetween substantially coextensive with the first and third substrates; and   an electronic circuit disposed and floating within the air gap and unattached to the first and third substrates.   
     
     
         2 . The stretchable radio frequency identification tag of  claim 1 , further comprising a second substrate disposed and floating within the air gap, the electronic circuit being disposed on the second substrate. 
     
     
         3 . The stretchable radio frequency identification tag of  claim 2 , further comprising a fourth substrate adjacent to and attached to the second substrate such that the electronic circuit is contained between the second substrate and the fourth substrate. 
     
     
         4 . The stretchable radio frequency identification tag of  claim 1 , wherein the air gap is at least partially filled with a cushioning material, wherein the cushioning material is non-conductive and non-adhesive, the cushioning material being located on the surface of the first substrate, the surface of the third substrate, or both.