Tunable wideband slot antennas based on printable graphene inks†
Nano-materials could endow electronics with some new functionalities. A slot antenna with a tunable bandwidth, consisting of a planar slot antenna with graphene at the end and a gap located between the ground and a small patch, is proposed in this study. The printed graphene inks deposited onto the antenna are made of graphene powder and graphene oxide aqueous dispersion. Graphene oxide sheets function as effective surfactants providing assistance to form uniform inks; meanwhile, the tailored blending proportions endow the graphene inks with optimized original resistances. Dried graphene inks display alterable electrical resistance under DC voltages and the variation in the resistance affects the radiation of the antenna. The slot antenna realizes an operating bandwidth (reflection coefficient |S11| < −10 dB) from 2.83 GHz to 6 GHz and a maximum frequency shift of 0.54 GHz after applying a DC voltage of less than 15 V. The graphene inks reported in this work integrate the dual advantages of graphene and graphene oxide. They not only provide stable and tunable graphene solution to antennas, but also could expand their applications in many other fields of electronic devices.