Nanotube RFID

Nanotube RFID

Nanotube

Carbon Nanotubes (CNT) are tube shaped material, which is made up of carbon having diameter less than 1nm(nanometer scale). The carbon atoms are arranged in hexagonal shape. Nanotubes are constructed with the ratio of 132000000:1(length to diameter ratio).  It has so many properties which can be useful in many fields such as nanotechnology, electronics etc. The allotropes of`carbon are diamond, buckyballs, graphite, carbon nanotube. The cross section of human hair is 80000 larger than carbon nanotube .From the name itself, it is clear that tube like structure having one atom thick sheet of carbon atom as their walls. These sheets are rolled at some specific angles. The properties of nanotubes are determined by this rolling angle and radius.

History

• In 1952 L.V Radushkevich and Lukyanovich published a paper in the soviet journal of physical chemistry. This paper contains the clear images of 50nm diameter tubes made up of carbon. In 1976 Oberlin, Endo, and Koyama published a paper containing clear images of hollow carbon fibers having diameter in the nanoscale range. In 1979, John Abrahamson published a paper at the biennial conference of carbon which contains details about the evidence of carbon nanotubes. In this paper the carbon nanotube  is described as carbon fibers.  In 1981, Soviet Scientists presented the details of structural andchemical characterization of carbon. The scientists suggested that, it is possible to produce carbon multilayer tubular crystals by rolling graphene layer into cylinders. The two possibilities of arrangements they suggested are armchair nanotube (circular) and  chiral tube (helical). In 1987, Howard.G.Tennet  got U.S patent for the production of cylindrical discreate carbon fibrils. In 1991, Japanese electron microscopist Sumio Ligima discovered multi walled carbon nanotubes.

Classification of Carbon Nanotubes

The Carbon Nanotubes (CNT) is classified into two.They are :-

• Single-walled Nanotubes (SWNT)
• Multi-walled Nanotubes (MWNT)                  

The figure below shows the Single-walled Nanotubes(SWNT) and Multi-walled Nanotubes(MWNT)

Other Carbon Nanotube structures are Torus, Nanobud, Graphenated Carbon Nanotubes(g-CNT), Nitrogen doped Carbon Nanotubes (N-CNTs), Peapod, Cup-Stacked carbon Nanotubes.

Single-walled Nanotubes (SWNT) 

It consists of only one layer of carbon. Most of the single walled nanotubes having diameter of 1nm. The structure is like wrapping a one atom thick layer of carbon into cylinder. They shows metallic and semiconducting behavior depending upon their geometry.The way of wrapping is represented by indices (n,m). This is called as chiral vector. n and m denotes the number of unit vector along the two directions.The nanotubes are called as “zigzag”, if m=0 and the nanotubes are called “armchair”,if n=m. otherwise they are called as “chiral”. 

Multi-walled Nanotubes (MWNT) 

It consists of two or more layers of carbon. i.e multiple rolled layers of carbon. There are two models which is used to describe the structure of multi-walled nanotubes. They are:-

• Russian Doll Model :- In this model, the sheets of graphite are arranged in concentric cylinders.
• Parchment Model :- In this model, a single sheet of graphite are rolled in around itself just like a rolled newspaper.

Properties of Carbon Nanotubes

• Strength :- They are the most strongest, stiffest, are flexible compared to other fiber materials  in terms of tensile strength and elastic modulus.
• Hardness :- The hardness and bulk modulus of carbon nano tubes are even higher than diamond. (Diamond is considered as the hardest material).
• Electrical Properties:- Carbon has a unique electronic structure. So it has high current carrying capacity. The electrical properties of carbon nanotube is strongly depends upon its geometry.
• Thermal Conductivity :- Carbon Nanotubes are good thermal conductors.

There are two problems related to carbon are given follows.

• Toxicity:- Under certain conditions nanotubes cross the barriers of membranes . It will adversely affects the  human beings which may lead cancer, lung disease and cardiovascular effects.
• Crystallographic defect :- This defect adversely affects the material properties. It causes the formation of atomic vacancies, reducing the tensile strengths. It also affects the electrical properties and thermal properties of nanotubes.

There are three methods which is used for the production of Carbon Nanotubes such as Arc Discharge Method, Laser Ablation, Chemical Vapour Deposition (CVD).

RFID- Radio Frequency Identification

The Radio Frequency Identification (RFID) is a technology which uses radio waves which transfer the data between electronic reader and movable item. It is used for so many purposes such as  identification , track, categorize etc. It is a small electronics device which consists of small chip and antenna and the chip is capable to carry 2000 bytes of data. The technology is same as that of the identification of barcode, magnetic strip on the ATM card or credit card. Just like this, the RFID device scanned for retrieving the information. The main advantage of the  RFID device is that there is no need to place the device precisely to the scanner. It is fast and reliable technology  which does not require line of sight between electronic reader and movable item. The RFID device will work within few feets of the scanner. For the identification of barcode, first of all to make sure that barcode can be read or not and for the identification of magnetic strip of ATM or credit card, it require a special reader. RFID tags are intelligent barcodes which means it communicate with the electronic reader. This electronic reader is connected to the network system and this will send the information to the retailer.

The main components of RFID are:-

• RFID tag
• RFID antenna
• RFID reader
• RFID station

The small chip inside label will send the information, when the label is exposed to radio waves. RFID tag consists of chips which holds the information about the object, antenna which is used to transmit radio waves, package which is used to encase the chip and antenna. There are two types of tags. They area active tags and passive tags. Active tag contains a battery which give power to the microchip circuit.RFID tag send strong signal with the aid of this battery. Passive tags have no battery. It gets power from the electronic reader. The electromagnetic waves send by electronic reader produces a current in the antenna of the tag .It helps to power the microchip. The main problems are tag collision and reader collision. When the signals from two or more electronic reader overlap, the tag can’t respond to simultaneous queries which leads to reader collision. If more tags are present in a small area, then it will lead to tag collision.

Nanotube RFID

Nanotube RFID (Radiiofrequency Identification) is a leading technology which use to develop carbon nanotubes for radio frequency identification tags. Thet are printed transmitters which allows  quck scanning of the products.  There are lots of properties of the nanotube which can be used for the Nanotube Radio Frequency Identification. The RFID have so many applications such as identification, track products, librarybooks etc. Currently the tag is madeup of silicon. It is too expensive. The cost can be reduced if the tags are made with plastics. Research is going on to develop cheap RFID tags. Researchers develop semiconducting ink which is made up of carbon nanotubes that can hold electric charge. They try to integrate more data in the small tags. This will reduces the cost while comparing with RFID which is madeup of silicon. This will replace the barcodes and silicon based RFID. This makes the carbon nanotubes RFID more popular. Nanotube RFID are passive tags. i.e The tags get the power from the reader and return information to the reader. So it has a very great life time because there is no battery integrates within the circuit. Whenever the radiowaves from the reader hits the tag,they will get charged up and sent the information to the reader. 

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In some places (South Korea), the RFID tags are printed in plastic films. They just use the combinations of industrial materials such as roll to roll printing, ink-jet printing, etc.. The carbon nanotube RFID uses inks containing carbon nanotubes deposit on the circuit components such as transistors or capacitors in the RFID tags. This is the first product that  uses  the printed transistors which is made from carbon nanotubes. Research is still going on to develop nanotubes  inks. But the only product developed is film for display electrodes.  Scientists says that, to make good quality nanotube ink, the ink must be uniform and viscous enough to print. But it is costly to produce.  The transistors using nanotube ink is difficult to produce because of several reasons. The challenging thing is that printing of large number of small transistors with nanotube inks with better alignment is a difficult process.Another problem is that the making of transistor arrays which control the display with nanotube ink is a challenging process. But still the research is going on to produce display control circuits with carbon nanotube transistors.