Printed UHF RFID antennas with high efficiencies using nano-particle silver ink

One of the most popular targets of conductive ink technology is to print RFID tag antennas. However, the printed RFID antennas, manufactured by conductive silver ink which is generally based on micro-sized silver particles, have lower conductivity and consequently lower radiation efficiency than those by conventional copper etching method. This work demonstrates nano-particle conductive silver ink that is capable of printing UHF RFID antennas with improved radiation efficiency. Compared with commercial micro-particle silver ink, the solid content of metal is much higher in the proposed nano-particle silver ink, leading to better electrical properties. Two types of dipole antennas are printed with the proposed nano-particle as well as with commercial micro-particle inks. Also, the same antennas are fabricated by copper etching. With these conductive inks, a straight and a meandered dipole antennas are fabricated and their radiation efficiencies are measured with the Wheeler cap method. Experimental results show that the radiation efficiencies of the antennas based on nano-particle silver ink are superior to those printed with the micro-particle silver ink, and are comparable to those of popular copper antennas.