I don’t believe that this is possible. A transponder that is only 2 millimeters in size would have a very tiny antenna. Antenna size relates directly to read range, because a smaller antenna can not harvest as much energy from a reader as a larger antenna can. So a transponder that small would have a read range of just a few millimeters.
Perhaps one of our readers might know something I don’t, however. If anyone is aware of a tiny passive tag that can be read from a distance of 5 meters or more, and that would be useful for this particular application, please post information about it below. Thanks.
—Mark Roberti, Founder and Editor, RFID Journal