I did end up making a working cloth RFID tag. This is a 2×3 inch iron-on patch with an antenna coil made of conductive thread. I sewed the bulk of the antenna by machine (and it would have been thicker if my thread hadn’t broke) then I did the more intricate bits by hand. The antenna itself is actually conductive only on one side, since I had insulating thread in the bobbin. I ran the conductive thread back from the outside of the coil to the center of the tag by sewing on the opposite side, so as not to short-circuit the coil. The black blob is an ATtiny85 microcontroller in a SOIC-8 package. In this tag, I attached the chip to the antenna using conductive epoxy. In my next prototype, I’ll probably use crimp beads as Leah Buechley suggests. The antenna should also really use more ‘turns’ of thread. This tag works with my Parallax RFID reader, but the range is only a few millimeters. On the right is a larger coil I was sewing for practice. This one would have been larger too, but I had problems with the thread breaking. I plan to make more prototype RFID tags, both to practice my sewing and to try and increase the range. (via Soft RFID tags and cuddly plushies : scanlime)