Ink the key to printed electronics
The first commercial printed electronics product, a battery tester, is on its way onto the market, but at Acreo Swedish ICT research is in full flow to develop ink that will have many different applications, in sunshine and in rain.
A thin strip is placed over the terminals of the car battery, and on the display in the centre you will see the charge remaining, as a percentage. The battery tester is the first commercial printed electronics product and in it is the concrete result of the advanced material research at the International Interdisciplinary Laboratory for Advanced Functional Materials (AFM).
Other applications that are on their way are, for example, the printed labels that Ericsson strategist Jan Hederén and Peter Dyreklev of Acreo demonstrated at CES, the major consumer electronics show in Las Vegas last winter. You touch a label on a poster for a concert and get all the information about the time, place, date and tickets direct to an app on your telephone. You touch a label on an item of food in the shop and you get information on its contents, how the packaging should be transported and at what temperature. Touch a place on a map and get directions straight onto your mobile. There are a multitude of possibilities.
Another example is dynamic QR codes, where a sensor can change the code so that you get a new reading.
“For example it is possible to send out the QR code with the morning papers and to receive hundreds of thousands of measurements from the public in no time, for environmental mapping,” says Peter Dyreklev, project manager at Acreo.
But none of this would work if it was not for electronic inks, the media that replaces graphical inks in printing presses and which also are electrically conductive. The research is being conducted at Acreo Swedish ICT in close collaboration with materials researchers at Linköping University. Acreo is doing the research and development to bridge the gap between academic research and commercialisation.
“We are developing printed electrochemical components; this deals primarily with electrochromic displays,” says Mats Sandberg, researcher at Acreo.
The key material in the electrochemical components is the electrolyte. In the most common electrochemical components – normal batteries or electrolytic condensers – the actual electrolyte are hermetically sealed in a metal casing. But this is not the case for the printed displays. Instead this type of electrochemical cell has to function without hermetic encapsulation both in damp and dry environments, so to say both in sunshine and in rain.
“Another challenge is that the material must be non-hazardous when handled throughout the whole chain; large amounts of the material must be handled by the manufacturer, consumers and eventually those who deal with waste,” says Mr Sandberg.
Some other critical properties of the electronic ink are that it must not dry in the press but must dry rapidly when it reaches the substrate. It must spread over the surface at just the right speed, be compatible with other materials, attach itself to the layer beneath and it must also have good mechanical properties – durable and pliable.
But solutions are on the way, though Mr Sandberg would rather not get into which materials that will involve.
“Well, they are based on polyelectrolytes, I can say that much.
Together with researchers from AFM he has also developed a method of measuring the conductive capability of a UV-cured electrolyte coating and one challenge he is now working with, together with the department of organic chemistry, is the study of the chemistry of the curing of ink.
“The systems for UV curing used for graphic printing ink are good enough for bonding pigment, but it does not work well enough for functional printing ink. In order for the electronic printing ink to harden rapidly enough we need to develop new bonding agent chemistry,” Mr Sandberg explains.
But solutions are on the way, and in the future we will see a number of new applications where printed electronics communicate with mobile telephones and where different objects communicate with each other and with us, through the “Internet of Things”. The ink is the secret agent without which none of it would work.
Related Links (LiU News)
Energy storage with printed electronics, about Modulit
Acreo Swedish ICT AB is an innovative research institute with 135 employees in Kista, Gothenburg, Norrköping and Hudiksvall. In Norrköping the focus is on printed electronics, and scientists there share premises in Kåkenhus Building on Campus Norrköping with the Laboratory of Organic Electronics, led by Professor Magnus Berggren.
Mr Sandberg is a chemical engineer with a PhD in polymer chemistry. He has been working at Acreo on the development of materials platforms for printed electronics since 2006. Since 2013 he has also been working part-time as an adjunct senior lecturer in the Laboratory of Organic Electronics at LiU.
Dr Sandberg also coordinates the Modulit project, financed by the Swedish Energy Agency, where in conjunction with researchers from several universities, including Linköping University, he will develop integrated energy storage modules in printed electronics.
Last updated: Wed Jun 04 14:27:08 CEST 2014