Behind the buzz and beyond the hype:
Our Nanowerk-exclusive feature articles
Posted: Feb 15, 2011
Printed electronics widens its scope
(Nanowerk Spotlight) Printed electronics has its origins in conductive patterns printed as part of conventional electronics, forming flexible keyboards, antennas and so on. Then came fully printed testers on batteries, electronic skin patches and other devices made entirely by printing, including batteries and displays. A clear next step has been to modernise static print with the e-reader and the talking poster with animated, light emitting display and solar power. These are partly or almost wholly printed, with a clear roadmap to making them lower cost and more reliable and flexible by using printing more fully in their manufacture in future.
Making new products possible
However, we now see printed electronics and electrics certain to penetrate far more applications than anyone realised. For example, large batteries have often used a measure of printing of simple electrodes and connectors but much more sophisticated printing processes are being applied to next generation solid state batteries in such things as power tools and traction batteries for the booming electric car industry, even the electrolyte being deposited by print like processes. An important engine of this dramatic widening of the scope of printed electronics is new materials, particularly relatively low cost, non toxic ones with superlative electronic and electric properties from creation of light to sensing of specific gases and generation of power in various ways. A great deal of work is going on to develop these into electronic healthcare disposables for testing and drug administration, to take just two examples.
Colourful wide area solar cells
For example, Oxford Photovoltaics, a company recently spun out from the University of Oxford in the UK, has developed new solar cell technology that is manufactured from cheap, abundant, non-toxic and non-corrosive materials and can be scaled to any volume. Harnessing the sun's energy, the solar cells are printed onto glass or other surfaces, are available in a range of colours and could be ideal for new buildings where solar cells are incorporated into glazing panels and walls. By combining earlier research on artificial photosynthetic electrochemical solar cells and semiconducting plastics Oxford PV can now create manufacturable solid-state dye sensitized solar cells. The device is a form of thin film solar technology, a relatively new development in solar energy generation. Leading thin film technologies are currently hampered by the scarcity of minerals used. Other dye-sensitized solar cells are being held back by the volatile nature of liquid electrolytes. Oxford PV's technology replaces the liquid electrolyte with a solid organic semiconductor, enabling entire solar modules to be screen printed onto glass or other surfaces.
The technology was developed by Dr Henry Snaith, of Oxford University's Department of Physics, who said, "One of the great advantages is that we can process it over large areas very easily. You don't have to worry about extensive sealing and encapsulation, which is an issue for the electrolyte dye cell."
Avoiding wet electrolytes
Printing solids is valuable, or at least printing materials that can easily be turned into solids at low enough temperatures not to damage low cost plastic film substrates. For example, so called copper indium gallium diselenide CIGS solar cells provide to only source of electricity for elegant solar boats for up to 150 people made by Kopf Solarschiff in Germany.
The Kopf Solarschiff
Inorganic, organic and composite inks
Combining organic and inorganic chemicals is increasingly the way to go rather than a misguided approach that used to see purely organic chemicals taking over. To take one instance of this, GeorgiaTech has printed flexible transistor arrays using High K inorganic gate dielectric with organic layers. The Russians, Koreans and others are racing to make flexible colour e-readers usually by printing both inorganic and organic layers and also composites.
Clearly all this concerns much more than improving the typical package, poster, book or battery, though there is much more to come in these areas. For example, a bird book will emit the song of the bird you touch simply by having electronic inks in the picture. More radically, cars will glow in the dark and have far more passenger space, aircraft and submarines will monitor their complete outer surface and military vehicles that destroy missiles that hit them. The common factor here is smart skin. Increasingly the multiple electronic and electric layers that constitute smart skin will be printed to save cost and weight and improve performance. A precursor of this will be the Northrop Grumman unmanned surveillance airship recently ordered that will be covered with thin film photovoltaics to provide power. Traditional heavy solar cells on glass panels are not an option here.
Invisible, self-healing and edible electronics
Some of the new developments seem like magic such as invisible electronics and electrics thanks to transparent printed components or the printed metamaterials that bend light. Researchers are creating a new type of solar cell designed to self-repair like natural photosynthetic systems in plants by using carbon nanotubes and DNA, an approach aimed at increasing service life and reducing cost.
"We've created artificial photosystems using optical nanomaterials to harvest solar energy that is converted to electrical power," said Jong Hyun Choi, an assistant professor of mechanical engineering at Purdue University.
The design exploits the unusual electrical properties of structures called single-wall carbon nanotubes, using them as "molecular wires in light harvesting cells," said Choi, whose research group is based at the Birck Nanotechnology and Bindley Bioscience centers at Purdue's Discovery Park. Nanotubes are increasingly put down in the form of printing inks for high speed and wide area. beyond that, several companies have patented forms of edible printed electronics for use in healthcare and novelties.
Travel and transportation
Printed electronics is starting to have a huge impact in travel and transportation even before those solid state printed traction batteries for electric vehicles are ready. Light aircraft are increasingly all electric with printing involved in the supercapacitors employed as well as the solar wings. T-Ink combines printing and laminating to save up to 40% of cost, space and weight of instrument and control clusters to appear in the next electric cars. Certain small orders for printed and partly printed electronics in 2010 were of deep significance. For example, the Kovio order for disposable electronic train tickets in Los Angeles saw formidable printed nano silicon electronics in the form of over 1000 transistors printed by ink jet and screen printing onto stainless steel foil. Being compatible with the world's most popular RFID specification ISO 14443 which was designed for silicon chips, this analog-digital circuit was a tour de force announcing to the world that a huge variety of the simpler integrated circuits can now be replaced by lower cost, more flexible and more robust printing albeit on stainless steel foil because of the high temperature anneal currently required.
Unique event revealing trends and successes
The uniquely comprehensive IDTechEx event Printed Electronics Europe in Düsseldorf Germany 5-6 April will reveal an exceptional amount about these new successes and possibilities. Many end users and potential end users will firmly place the emphasis on applications rather than obscure academic aspects. The two day conference and tradeshow encompasses an awards dinner and presentations in the exhibition area plus major in-depth conferences alongside on printed electronics and on the new thin film photovoltaics. There are optional masterclasses and visits to local centres of excellence in the subject, on the day before and the day after.
Samples not just promises
Equally unique and valuable will be the famous demonstrations and the profusion of otherwise unobtainable working samples for attendees, including radically new product ideas. No longer are engineers the centre of attention as they make modest improvements to existing technologies using printed electronics: creative product designers are now in the driving seat and the results are startling. Hear from giants such as snackfood company Mars, major retailer Metro, outdoor advertiser JCDecaux, phone leader Nokia, the US Army and other users but also the most creative and successful suppliers such as the T-Ink mentioned above, FutureShape with large area smart printed textiles and InteractiveWear. Then there are companies that are both supplier and user such as Samsung of Korea, this being a truly global event.