3D Printing Antennae with Graphene: RFID Research from the UK

An inter-institutional research team in Manchester, UK has released a paper for publication in Applied Physics Letters in which they explore the potential for the use of high conductivity graphene as the ink of choice in printing radio frequency identification (RFID) antennae. Graphene is being hailed as the new wonder material from many different directions. The paper itself, "Binder-free highly conductive graphene laminate for low cost printed radio frequency applications," is highly complex and requires a specialized knowledge set, and a great deal of personal fortitude, to read in its entirety.
In preparation of printing, graphene inks are either dispersed directly into solvents with no binder or a binder such as ethyl cellulose is utilized. When the ink is prepared with a binder, it has a higher conductivity rating but it is unsuitable for application on heat-sensitive substrates (such as paper...or your cat!). The binder-free version, however, has a significantly lower capacity for conductivity, and research, therefore, is directed at maximizing conductivity while also maintaining a lower temperature processing.
In their paper, the researchers presented a technique purported to enhance the conductivity of binder-free graphene ink for screen printing on an industrial scale. The technique they have developed for improving the conductivity of the graphene laminate results in an improvement in conductivity of over 50 times. In addition, they have demonstrated its effectiveness in terms of radiation and propose that it is a valuable prospective material for use in RFID as well as other radio frequency applications.
The binder that is used to create the graphene ink is designed to ease the flow of conductivity between its component nano flakes. The binder creates the continuity necessary for the conduction, however, it is also its own worst enemy as the binding material itself is an insulator, i.e., something that slows conductivity. The reason that the compression rolling technique is useful for improving the conductivity of binder-based graphene inks is that after it has been rolled, the graphene nano flakes are much more dense and a laminate is formed.
The researchers noted:

"Not only [does] the conductivity increase significantly with compression but also the sheet resistance of the graphene laminate reduces. In antenna applications, especially in RF band, sheet resistance matters more...Due to the flexibility of graphene laminate, the antenna is flexible when printed on paper or plastic, which is quite important for flexible electronics like wearable and RFID applications."

The smoothing of the surface architecture of the graphene by the rolling technique utilized by the researchers creates lowered contact resistance and a smooth pathway for electron transport. To further investigate the radio frequency radiation properties, the researchers created a half-wavelength dipole antenna. Antenna patterns were screen printed onto a sheet of normal paper and a series of tests were run in order to determine the level of performance of the screen printed graphene laminate.
While there was good impedance matching, further tests are needed because the results only indicate that power is transmitted from the antenna to the source but not necessarily that the transmitted power is radiated in an effective manner to the free space.


Read more about this research: http://3dprint.com/68774/graphene-3d-printing-antennae/
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