Abstract
In this paper, we report highly conductive, highly flexible, light weight and low cost printed graphene for wireless wearable communications applications. As a proof of concept, printed graphene enabled transmission lines and antennas on paper substrates were designed, fabricated and characterized. To explore its potentials in wearable communications applications, mechanically flexible transmission lines and antennas under various bended cases were experimentally studied. The measurement results demonstrate that the printed graphene can be used for RF signal transmitting, radiating and receiving, which represents some of the essential functionalities of RF signal processing in wireless wearable communications systems. Furthermore, the printed graphene can be processed at low temperature so that it is compatible with heat-sensitive flexible materials like papers and textiles. This work brings a step closer to the prospect to implement graphene enabled low cost and environmentally friendly wireless wearable communications systems in the near future.
Highlights
Carbon nanotubes, with typical sheet resistance above 50 Ω/sq, due to high junction resistance between overlapped nanotubes[17,18], is still not conductive enough to meet practical RF circuit requirements
We briefly introduce the preparation of printed graphene, and the details are included in the Method section[34]
We have presented highly conductive and flexible printed graphene TLs and antennas using graphene nanoflakes aiming for wireless wearable communications applications
Summary
With typical sheet resistance above 50 Ω/sq, due to high junction resistance between overlapped nanotubes[17,18], is still not conductive enough to meet practical RF circuit requirements. One is binder-free technique which disperses the graphene directly in solvents such as N-Methyl-2-pyrrolidone or Dimethylformamide (NMP/DMF) without adding any binder[31,32], whereas the other uses binders like ethyl cellulose (EC)[29,33] Even though the latter technique can offer higher conductivity, it requires high-temperature thermal annealing, making it incompatible with heat-sensitive substrates like papers and textiles[18]. The measured conductivity from this technique reaches 4.3 × 104 S/m, which is almost double of 2.5 × 104 S/m from previously reported RGO (reduced graphene oxide) with binder and 10 times higher than that from binder-free method[29,32] In this report, this highly conductive printed graphene is further utilized to construct transmission lines and antennas on a flexible substrate such as paper. Together with the aforementioned progress of graphene active RF devices, a truly all graphene enabled wireless wearable communications system can be expected in the near future
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