Silver nanowire antenna printed on polymer and paper substrates

Dramatic spread is going on high frequency operation device, such as mobile phones, wireless LAN, and radio frequency identification (RFID). Especially, the antenna is the most important element in the high-frequency operation device, and has been studied around the world. The printed antenna on flexible substrate is remarkable, since such printed antenna package is thinner, lighter and cheaper than conventional antenna prepared by etching process. In addition, printing process is a highly efficient and eco-friendly method. Silver nanowires are conductive and printable, and are thus promising materials in the field of printed electronics. However, the resistivity of printed lines of silver nanowires is higher than those of silver particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotube, and graphenes. Here we report that signal losses of printed silver nanowire lines in the high-frequency radio were lower than those of etched copper foil antennas, even though the resistivity of silver nanowire lines was 43-71 μΩcm, which was much higher than that of etched copper foil (2μΩcm). This was because the surface of printed silver nanowire antennas were much smoother than those of etched copper foil antennas. When printed silver nanowire antennas were heated at 100 °C, they achieved much lower signal loss than those of silver paste antennas comprising microparticies, nanoparticies, and flakes. Such a low temperature process is advantageous antennas on polyethylene terephthalate (PET) film and paper substrate. Furthermore, using a low temperature process, we succeeded in remote control of a commercial radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a PET film.