42 research outputs found
Near-Field UHF RFID Transponder with a Screen-Printed Graphene Antenna
As a method of producing RFID tags, printed graphene provides a low-cost and
eco-friendly alternative to the etching of aluminum or copper. The high
resistivity of graphene, however, sets a challenge for the antenna design. In
practice, it has led to using very large antennas in the UHF RFID far field
tags demonstrated before. Using inductive near field as the coupling method
between the reader and the tag is an alternative to the radiating far field
also at UHF. The read range of such a near field tag is very short, but, on the
other hand, the tag is extremely simple and small. In this paper, near field
UHF RFID transponders with screen-printed graphene antennas are presented and
the effect of the dimensions of the tag and the attachment method of the
microchip studied. The attachment of the microchip is an important step of the
fabrication process of a tag that has its impact on the final cost of a tag. Of
the tags demonstrated, even the smallest one with the outer dimensions of 21 mm
* 18 mm and the chip attached with isotropic conductive adhesive (ICA) was
readable from a distance of 10 mm with an RF power marginal of 19 dB, which
demonstrates that an operational and small graphene-based UHF RFID tag can be
fabricated with low-cost industrial processes.Comment: 8 pages, 9 figures. IEEE Transactions on Components, Packaging and
Manufacturing Technology, 201
Graphene-Flakes Printed Wideband Elliptical Dipole Antenna for Low Cost Wireless Communications Applications
This letter presents the design, manufacturing and operational performance of
a graphene-flakes based screenprinted wideband elliptical dipole antenna
operating from 2 GHz up to 5 GHz for low cost wireless communications
applications. To investigate radio frequency (RF) conductivity of the printed
graphene, a coplanar waveguide (CPW) test structure was designed, fabricated
and tested in the frequency range from 1 GHz to 20 GHz. Antenna and CPW were
screen-printed on Kapton substrates using a graphene paste formulated with a
graphene to binder ratio of 1:2. A combination of thermal treatment and
subsequent compression rolling is utilized to further decrease the sheet
resistance for printed graphene structures, ultimately reaching 4 Ohm/sq. at 10
{\mu}m thicknesses. For the graphene-flakes printed antenna an antenna
efficiency of 60% is obtained. The measured maximum antenna gain is 2.3 dBi at
4.8 GHz. Thus the graphene-flakes printed antenna adds a total loss of only 3.1
dB to an RF link when compared to the same structure screen-printed for
reference with a commercial silver ink. This shows that the electrical
performance of screen-printed graphene flakes, which also does not degrade
after repeated bending, is suitable for realizing low-cost wearable RF wireless
communication devices.Comment: Accepted, in press (online preview available
Single-Walled Carbon Nanotube Network Field Effect Transistor as a Humidity Sensor
Single-walled carbon nanotube network field effect transistors were fabricated and studied as humidity sensors. Sensing responses were altered by changing the gate voltage. At the open channel state (negative gate voltage), humidity pulse resulted in the decrease of the source-drain current, and, vice versa, the increase in the source-drain current was observed at the positive gate voltage. This effect was explained by the electron-donating nature of water molecules. The operation speed and signal intensity was found to be dependent on the gate voltage polarity. The positive or negative change in current with humidity pulse at zero-gate voltage was found to depend on the previous state of the gate electrode (positive or negative voltage, respectively). Those characteristics were explained by the charge traps in the gate dielectric altering the effective gate voltage, which influenced the operation of field effect transistor.Peer reviewe
Screen-printed and spray coated graphene-based RFID transponders
We report Ultra-High-Frequency (UHF, 800MHz-1GHz) Radio Frequency Identification (RFID) transponders consisting of printed dipole antennas combined with RFID microchips. These are fabricated on Kapton via screen printing and on paper via spray coating, using inks obtained via microfluidization of graphite. We introduce a hybrid antenna structure, where an Al loop (small compared to the overall size of the antenna) is connected to a microchip with the double function of matching the impedances of antenna and microchip and avoiding bonding between exfoliated graphite and chip. The transponders have reading distance11m at UHF RFID frequencies, larger than previously reported for graphene-based RFID and comparable with commercial transponders based on metallic antenna