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Printed Electronics World
Posted on March 21, 2005 by  & 

Remarkable innovations by VTT Finland

VTT has over 2500 people and the polymer electronics group of about 15 people is working on utilizing high volume manufacturing techniques to make inherently conducting polymer based devices. Tapio Makela told us at a recent conference that they are studying gravure and flexo. Primary interest is sensors such as humidity and time-temperature. Using an engraved cylinder they can make 100 micron lines of conductive polymer, with flexo they get 50 microns. This has been used to make all polymer organic Field Effect transistors OFET but not all the processing is by fast printing. A fully reel to reel process is being developed. Multilayer electronic constructions have been made using gravure. Flexible OLEDs for decorative use are being developed but they only last for a few days if unprotected. Low cost is the target so the current expensive ways of extending life are not of interest. Indeed 50% of the cost is the PET ITO conductively coated substrate.
VTT notes that inherently conductive polymers such as PANI are sensitive to PH changes etc.

Breakthrough in time temperature indicators

VTT has developed a colour and conductance changing indicator that can have large area and be printed on packaging unlike today's chemical TTI's. However, it would need approvals before use in food or drug packaging. I-dedocecyl alcohol is used. The electrical transition can be predetermined to any three degree interval and can go from conductive to insulating or the opposite at the chosen transition. This can be electrically detected by contactless interrogation even if the device is buried in the packaging. Cost, at around 0.01 cents, is projected to a fraction of today's chemical TTI's which simply show a dot changing colour.

Smart packaging electronic games

A jungle game asks the child what foods the pictured animals eat. It is fully printable in 7-8 layers with a 5V battery. Response is by changing colour on a package when the player gives the right answer. It uses Al and Ag conductive layers for metal electrodes, a PANI-T heater, thermochromic ink, a 5V 100mA battery and a connection made by pressing on the surface. A hockey game on a four pack of beer cans uses similar layers to give an indicated score when the player wins.
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