Miniature on skin passive UHF RFID antenna sticker

Abstract

Passive Radio Frequency Identification (RFID) in recent years has been more widely suggested for medical use with different types of wearable antenna designs. However, wearable passive RFID technology has always been limited by a few key constraints (primarily size) when trying to overcome the variable human body's dielectric properties to produce a high read range antenna design. Here we present an on skin passive RFID antenna design, three centimetres in diameter with a read range near two meters on the human body. With slight adjustments to the polyutherane thickness, the original sticker design can negate the difference between the variable human body dielectric properties within subject groups with only slight loses in antenna read range. It was more cost effective to vary the thickness of the breathable polyutherane used as the tag substrate to achieve a resonance within the European UHF RFID frequency range (as well as to increase the read range capability) than to redesign the antenna. Most variability was seen in subjects with high muscle to fat ratio; if the subject was highly muscular then the antenna polyutherane layer was increased to accommodate the increase in the subject's dielectric properties. This has led to a single passive RFID antenna design (two different polyutherane thicknesses) that can accommodate most people as a wearable design with numerous possible applications.