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Printed Electronics World
Posted on February 21, 2011 by  & 

Paper electronics ready for prime time

The term paper electronics refers to electronic and electric circuits printed onto paper - increasingly both at the same time. Paper electronics has its origins in the screen printing of electrodes onto battery separators for cylindrical batteries and it has been used for conductors and sensors in such things as T-Ink toys and novelties.
Paper electronics progressed into the manufacture of laminar batteries almost entirely made of paper, where Blue Spark Technologies is a leader. This type of battery powers an interactive cover for a recent edition of Canvas magazine for instance. It is a carbon zinc single use battery and these are also popular for active RFID and powering new electronic features on consumer goods, novelties and promotions.
Blue Spark Technologies has printed other devices on these batteries such as RFID antennas and it is willing to license its processes for incorporation in printed and conventional electrical and electronic products, there being cost and reliability benefits in multilayer structures without conventional interconnects. All these forms of printed electronics employ screen printing because the relatively thick pastes involved bridge the rough surface of paper.
We now have the capability to print conductors, resistors, capacitors, primitive sensors and displays and low power single-use batteries onto paper. For the market to multiply one hundredfold, we need diodes, most sensors, transistors, better displays, photovoltaics and other electrical and electronic components to be viably printable. Increasingly, that will be in one multilayer process, though the speed of progress varies. For example printing animated colour displays and even digital displays on paper has been done by about ten companies using electrochromic and ac electroluminescent technology but commercial success has been elusive, there being issues with appearance and life in some cases.
Nonetheless, Dr Peter Harrop, Chairman of IDTechEx says, "Electronics and electrics printed on paper or laminated into paper will be a major part of the $300 billion plus printed electronics market in twenty years from now."
At the largest event on printed electronics, the forthcoming "Printed Electronics Europe" in Düsseldorf Germany 5-6 April
paper electronics will be a major focus because it is now ready for prime time. About 15 presentations are relevant to paper electronics.
For example, consumer goods leader Mars and supermarket giant Metro Group of Germany will describe how they need paper electronics in point of sale material and other applications and the US Army will describe its needs and developments. Large area advertising giant JC Decaux of France will talk about its requirements. The optional masterclasses before and after the two day conference and exhibition will also explain the new advances with paper and what comes next.
BlueSpark Technologies and many others can be seen in both the exhibition and the conference.
In the main session, Karen K. Gleason, Alexander and I. Michael Kasser Professor of Chemical Engineering at Massachusetts Institute of Technology will speak on "Paper thin organic photovoltaic circuits fabricated directly onto everyday substrates". She notes that, "Paper offers substantial decreases in both cost and weight, even over plastic substrates. Paper photovoltaics can be rolled up for storage and shipment and can be readily installed with a staple gun. Fabrication on paper opens new venues for solar cells including folded window shades, wallpaper, documents, and currency."
Professor ArvedHübler of Chemnitz University of Technology, Germany will present on "Printed solar cells on paper? Why and how". Another form of energy harvesting comes from printing piezoelectrics, one of the topics to be covered by Professor ShashankPriya of VirginiaTech Center for Energy Harvesting Materials and Systems CEHMS. The large research centre ITRI in Taiwan shares its latest work on printed electronics.
Paper creates both opportunities and limitations. One of these is its poor thermal conductivity of paper limiting its use for uniform heating by means of resistor patterns but making it excellent for localized, directed heating.
Speaker Dr Harry Igbenehi of Flexible Electronics Concepts advises, "Paper's structure is of paramount importance in the evaluation of electronic devices on paper substrates. The relatively poor thermal conductivity and rough surface (as measured by AFM) introduce many unique challenges as well as opportunities. Non-obvious structural challenges include; localized degradation of paper's cellulose on contact with materials and solvents used in the electronic industry, sorption behaviour, permeability, and residual stress effects created by vacuum environments."
Other speakers point out that paper is biodegradable - very much an issue of the moment - and compatible with most packaging and media. With the graying of the population, the huge number of self-help medical testers, drug delivery devices and other treatments must be very low cost and disposable, making paper a prime candidate for their construction. Countries such as Russia, Italy and Japan are headed for up to 60% dependent elderly in the next forty years, enough to overwhelm existing medical services: disposable electronics and electrics must be widely deployed instead.
It is therefore interesting that Fraunhofer IFAM of Germany is talking on what it calls "INKtelligent printing of sensor structures". This includes strain gauges and thermocouples.
A number of new developments have rendered paper electronics much more widely applicable. Professor Elvira Fortunato of the New University of Lisbon will speak on "From e-paper to paper-e: latest progress". Her point is that so called e-paper is invariable plastic, the term referring to replacing paper books with e-readers where E-Ink of the USA will announce new colour versions at the event. By contrast, hernext step is the much wider deployment of intelligent paper. Her discovery is that paper can form the gate dielectric in printed transistors and she will report how this is progressing to commercialisation.
This is counterintuitive because, at first sight, one would think that the thickness of that dielectric would be very large if the paper substrate was used and therefore impractically high voltages must be applied but, for reasons not fully understood, these gates work well. Elegantly, paper acts as both substrate and gate dielectric.
On the other hand, Applied Materials of the USA will discuss silicon based flexible thin film transistor TFT technologies, initially on plastic. Professor Margit Härting of the University of Cape Town in South Africa will describe her rapid progress to commercialisation of printed crushed silicon on paper and other substrates. On the basis of "walk before you run" the first devices are diodes which can be the basis of many things, initially thermistors, but soon rectifiers, charge pumps, voltage dividers and so on. Transistor circuits are in the frame for later. A huge number of applications await those printing affordable but only moderately performing devices on paper.
New processing technologies help. The strong light pulses by NovaCentrix anneal inks at high temperatures without damaging the low cost low temperature substrates underneath. They will describe," Reducing screen-printed copper oxide to copper on paper substrates at industrial speeds in air". Indeed, the move from conductors made by vacuum processing or rare metals to lower cost copper is another new trend to be aired at the event.
Exhibitor Intrinsiq will demonstrate copper nanoparticle ink accepting photonic curing at room temperature in air. It is ready to print using industry standard commercial inkjet systems on a variety of substrates including paper.
Q-foil, a sensor technology developed by isiQiri interface technologies of Germany and being presented at the event, makes it possible to equip large areas with continuous photodetectors that are flexible and can sense the position of localized light and shadow areas with high precision.
The first application, an interactive projection screen called Q-screen, will hit the market end of this year. The audience can vote by shining laser guns at the giant screen and the electronics then presents the resulting statistics, for example. Such new technologies can be expected to appear on both paper and plastic film.
Presenters Thin Film Electronics of Sweden will show their paper games and cards with printed rewritable memory. Here the memory is printed on plastic film and laminated into paper media. Printechnologics also presents on this type of construction but for batteries, read only memory etc and they can also print devices directly onto paper.

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Posted on: February 21, 2011

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