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Posted: Mar 01, 2011

The rise of flexible electronics

(Nanowerk News) The silicon chip took over forty years to approach a $300 billion business today. Now there is a new form of electronics that will hit that figure in half the time because, unlike the silicon chip, it subsumes electrics such as lighting, batteries, solar cells and heaters, not just electronics. It is usually achieved by printing and its most vital characteristic is physical flexibility. Take that as meaning a variety of capabilities valued in the marketplace such as foldability, conformance to architectural features, stretchability and even the ability to be tightly rolled, worn, washed and waterproof. Some forms survive being hammered and even stabbed so, in the main, we are talking of putting electrics and electronics where they could never go before. Another aspect is biodegradability where needed, even printing electronics onto paper. Multilayer structures are increasingly possible, reducing the number of interconnects and the area needed and increasing reliability.
The world's largest event exploring this new world and what comes next is the IDTechEx Printed Electronics & Photovoltaics Europe 2011 taking place in Düsseldorf 5-6 April. The presentations give a guide as to the most vital aspects being brought to market. For example, mobile phone company Nokia will talk about its work on stretchable electronics, something more usually related to healthcare products. The Samsung speaker Dr Bonwon Koo refer to customers wanting to carry something small that give wide area viewing and how its record breaking flexible polymer dispersed liquid crystal (PDLC) displays are one route to that market need. They are driven by ink jet printed transistor backplanes.
Creating many new markets
Presenter Dr. Harry Zervos of IDTechEx points out that, "Flexibility and light weight open up many new markets. It will be easy to go to the local DIY shop and buy rolled or folded solar panels and fit them in the average family car to take them home. There will be no need to strengthen the home roof before installing such panels."
However, he counsels that there is still work to be done if the full potential is to be realised, not least by improving the efficiency of the solar cells - currently one tenth of the figure for today's heavy glass versions - and reducing the cost of some of the inks used.
Konarka, a leader in organic photovoltaics (OPV), will address its technical progress and commercial direction. For example, poor OPV efficiency and weather tolerance currently makes it inappropriate for power station replacement. By contrast, its extreme flexibility and relative safety with children make it excellent for toys, packaging, solar bags and more. Taken together, these markets are potentially as large as the "power station" dream - something only recently appreciated.
High speed electronic printing
CSIRO of Australia will report how high speed gravure can be employed to print such films and the technical University of Ilmenau will describe slot die coating to make them. G24 Innovations will give the latest on its reel to reel printed Dye Sensitised Solar Cells (DSSC) that are based on unusually low cost materials and have certain usefully unique properties. ISORG of France now offers a new generation of high performance, thin and flexible electronic photodetectors and image sensors with 3D product integration capability for a large range of markets (industry, consumer electronics, environment, medical and security). Others have printed flexible batteries, memory and other components. It is clear that a formidable repertoire of components for complex flexible electrical/electronic circuits is becoming available. Indeed, basic circuit modules are now demonstrated such as the HF digital analogue RFID on plastic film demonstrated by Sunchon University Korea. It deploys transistors and diodes. This is a toolkit that creative designers will die for.
Of course, not all of these features appear in every form of the new electronics but each creates a huge new market where the silicon chip and its many connections to bulky conventional electronics and electrics will never compete. Here we often have ultra low cost, extreme thinness and, where needed, wide area because the clunky batch production with small slow machines that familiar in the manufacture of today's electrics and electronics is partially or wholly replaced by reel to reel printing with the new electrically active inks. Even the mirror-like images created by certain fast letterpress technology can be tweaked to be useful electronically. Other regular presses can sometimes be used for both conventional graphics and electronics. Indeed, in its early stages this new electronics has been more often been about modernising printing than about replacing old electronic products.
Invisible electronics
A wide variety of transparent electrical and electronic components have now been printed, opening up the possibility of adding electrical and electronic functionality to almost anything by applying a transparent plastic film to the surface because these see through circuits and power supplies have been already printed onto it.
Smart skin, brand protection, unrolling displays
Here we have the ability to put smart skin on dirigible balloons and aircraft to harvest energy, sense condition - even store electrical energy. Here is apparel that electronically protects against counterfeiting and provides new features such as monitoring vital signs. Smart packaging, posters, point of sale displays and healthcare disposables increasingly speak, interact and have moving colour images and more. Here is the modernisation of anything that is printed conventionally: we add sound, changing surface texture, colour video and more. Yes, the predicted mobile phone will arrive that unrolls a big colour display and keyboard that also captures light to power the battery. It will spring back into the body of the phone when not needed, being very tightly rollable.
New applications
We are at the beginning of this new world, with modest initial victories such as rollable keyboards and moulded car antennas made possible by screen printed flexible metal patterns. We have conformal light emitting "ac electroluminescent" colour displays up to four meters high and one hundred meters long but also animated colour emitted from washable t-shirts. Animated printed posters with sound interactivity and other electronic features can be seen in the Tokyo subway this year, their power coming from capturing the low level of lighting available using printed OPV. They are unrolled and applied like a regular paper poster. Indeed paper versions are coming next, the present disposable versions being on plastic film. Apparel, bags and parasols that charge your phone are newly on the market.
Massachusetts Institute of Technology refers to "tortuous flexing and folding into three dimensional structures" using photovoltaics printed onto paper - part of the new "origami electronics". On the other hand, Platingtech will address large area printed textiles and their applications made possible by printed sensor structures and heating.
Andreas Roepert of Interactive Wear says, "Building wearable electronics applications calls for flexible and very robust components. Requirements for textile integration from requirements in consumer and industrial applications." He will report progress towards functions including fashion/sports, wellness/medical and safety/security using keypads, displays, heating pads, solar cells and RFID. He sees this new electronics reviving brands with startling new features and market awareness. Here, the sequence will be photovoltaics, then Organic Light Emitting Diode (OLED) displays then other displays being incorporated as they mature, he predicts.
Kent Displays reveals flexible bistable displays, retaining their image when the electric power is removed. Polymer Vision describes very different displays and both will emphasise the many applications emerging for these advances. Hitachi Chemical's new copper nanoparticle inks have been used to manufacture intricate flexible structures opening up the capability to print complex antennas, keypads and other flexible structures. Particle sizes range between 10 and 100 nm for these inks and conductivities achieved have reached values (6 µΩ) comparable to those achieved with bulk copper (3 µΩ) so a more affordable alternative to printed silver is now with us.
All the above companies - and many more - are presenting or exhibiting at the world's leading event on the subject, Printed Electronics & Photovoltaics Europe 2011 in Düsseldorf Germany on April 5-6. There will be optional masterclasses and visits to centres of excellence in the subject on the day before and the day after the two day conference and exhibition. There is an awards dinner - still time to apply - and many other opportunities to network and get free information and working samples.
Source: IDTechEx (Dr Peter Harrop)
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