Digitally Fabricated Epidermal Transfer Tattoo UHF Radio Frequency Identification Tags

This thesis focuses on the inkjet printing of UHF RFID tags in the form of transfer tattoos for use on the skin. Inkjet printing of these tags is proposed as a cheaper and more appropriate alternative to conventional etching.

The work seeks to assesses the performance of inkjet printed epidermal RFID tags using parameters such as read range, transmitted power and backscattered power. The effect of different printing parameters such as the number of conductive ink layers, sintering time and temperature on the performance of the tags are assessed by simulation and measurement. Additionally, techniques to reduce the volume of conductive ink used for the fabrication of the tag are also examined and compared with an aim to determine which has the best achieved read range and ink utilization balance. This would help to reduce the cost of fabrication of the tags.

Also, due to some defects being introduced to the tags during the printing process because of printing conditions and characteristics inherent to the printing technology, the effects of these defects on the performance of the printed tag is also examined by simulation and measurement. The robustness of the epidermal transfer tattoo tag was further experimentally determined by exposure to everyday use conditions and situations involving sweat and mechanical friction.

Finally, a diversity study on an inkjet printed tag integrated with a medical sticking plaster was performed. This involved the use of two to four tags placed horizontally and vertically in order to determine which orientation offers better read coverage in each of the diversity setups while a volunteer carried out a set of motions.