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Printed Electronics World
Posted on January 16, 2009 by  & 

Cheap, printed RFID tags performing simple functions may be here soon

Printed RFID tags that could be cheap enough to use on consumable packaging to monitor temperature, store and transmit data may only be a year way claim scientists at the Fraunhofer Institute of Integrated Systems and Device Technology IISB in Erlangen.
 
With continuous technological advances, over the years we have seen televisions transform from the bulky square objects that dominated our living rooms to sleek thinner, lighter and aesthetically pleasing devices that easily adorn our walls or coffee tables.
 
If you were to look inside you would see fine conductor paths and transistors that supply the electricity needed to switch the pixels on the screen on and off. These circuits are manufactured layer by layer, usually by photolithography. The materials are deposited onto the entire surface of a substrate which needs to be flat to start with and covered with photoresist, which is exposed to light at specific points using a mask. The exposed photoresist alters its chemical properties - It becomes soluble and can be easily removed. The layer to be structured returns to the surface and can be etched away. However, the parts of the layer still covered with photoresist remain intact. One major disadvantage of this process is that a large fraction of the deposited material is not used. A more cost-efficient and resource-saving method is to deposit the material by printing only in places where it will actually be needed later.
 
 
Printed electronics already exists in the form of conductor paths and devices made from polymers. However, their electrical properties cannot compete with those of inorganic materials. The charge carriers in the polymers travel more slowly, with the result that a printed RFID tag, for example, will have a shorter transmission range than a conventional one. Moreover, polymers tend to react more sensitively to moisture and UV light.
 
Researchers at the Fraunhofer Institute of Integrated Systems and Device Technology IISB in Erlangen claim to have developed a process line in which electron devices can be printed from inorganic materials using an ink jet similar to those in any office printer. They use ink made of nanoparticles and add a stabilizer so that the particles can be easily processed and do not clump together.
 
The researchers hope that they will be able to print circuits performing simple functions in about a year's time.
 
IISB group manager Dr. Michael Jank says, "We expect printed products to cost around 50 percent less than silicon-based ones in the case of simple circuits. Printed RFID tags should then be cheap enough to be attached to the packaging of low-cost products such as yogurts, where they can then monitor the temperature, and store and transmit data."
 
 
Top image: In order for printed electron devices to work, the researchers need to match the properties of the ink and the substrate surface to one another. The untreated insulator (left) is difficult to wet, unlike the surface-treated insulator (right). (Source: the Fraunhofer Institute of Integrated Systems and Device Technology IISB).
 
Reference: The Fraunhofer Institute of Integrated Systems and Device Technology IISB.
 
To get a wider picture read Dr Peter Harrop's earlier article New strategy for printed electronics.
 
 
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