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Printed electronics: Not just blinking beer bottles

Flexible innovation, in every sense of the word

"Printed electronics" is one of those terms one sees being bandied about without really knowing what it means or why it's important. The premise of using printing techniques to create electrical circuits isn't hard to comprehend, but not everyone agrees on what comprises a "printing technique" or why you might want to use one, so El Reg chatted to three companies at the forefront of the field.

According to these firms, the new printing technique is going to change the literal fabric upon which the electronics industry rests. That's important as it's not the electronics which change as a result of the printing process, but rather the material on which those electronics rest. So instead of being etched on silicon the circuits can be laid onto steel, plastic, or even paper, and it's that change of substrate which links all the various techniques and makes printed electronics so exciting.

Starting at one end of the complexity spectrum, using standard offset lithography printers loaded with conductive ink, is Novalia, which has been making interactive posters and tissue boxes for the last half decade by printing electronic circuits onto paper and card:

Novalia is adamant that only standard printing techniques, and machinery, should be used to keep things simple, meaning that solid-state electronics are still needed to complete a product but costs are incredibly low.

For example, in the video above, the chip which plays the tune is cheap silicon, but the capacitance-detecting circuit is printed on the cardboard of the box or the back of the posters adorning the walls of the company's Cambridge offices. Novalia reckons it can turn anything into a touch-sensitive surface, and points out that cardboard is a perfectly sensible construction material once one can embed electronics into it (think posh gift box, not corrugated card).

Not that one needs to think of an entire product, Novalia has made wallpaper for the inside of ('leccy generating) windmills with numbered tracks to which sensors can be attached, creating a signal bus down the inside wall and replacing bundles of wires in the process.

Novalia's approach is limited; output is mostly audio as that's cheap and easy to do once one has solved the connections between printed and solid-state circuits (conductive glue, apparently, but much of Novalia's IP is in that area). Novalia does have some demonstrators using thermally triggered colour-changing ink, and is working with Bluetooth LE to output touch results to a nearby PC, but prefers to concentrate on the basics of using standard printing equipment to make electronics.

This is in contrast to Silicon Valley's Kovio, which steps away from standard printing equipment but still uses ink-jet techniques to lay down working RFID chips onto a flexible steel substrate.

The mechanism is the same as a desktop ink-jet, only instead of ink the jets squirt out ca conductor into wires as little as eight microns thick, making up chips which will run up to 40MHz or so. But Kovio can print a lot of them very cheaply and hopes to get the Near Field Communications (NFC) standard extended to include its vision of printed RF barcodes, powered by induction from the reading device and able to respond with a standardised serial number.

The company also makes traditional NFC chips, but prices those between 10 and 15 pence a time while a printed tag costs around a third of that. Printed tags are larger; cheapo NFC tags look like to the naked eye like grains of sand while a printed tag is a few millimetres square, but Kovio turns this into an advantage arguing that it's easier to attach sensors to its bigger tags which are also cheaper to handle than their diminutive, silicon-based, cousins.

Kovio's steel substrate is flexible because it's thin, but it has to be steel to survive the curing process which involves baking the ink into place. To get electronics onto plastic one has to take a step further, or perhaps back, from printing techniques.

Such a step is taken by PragmatIC, another Cambridge-based company and one we've mentioned before thanks to their light-up beer bottles and induction-powered screens. PragmatIC doesn't so much print electronics as imprint them, creating a sandwich of materials and then, using a pre-cut die, press down and carve out the shape required.

That might be taking the concept a long way from printing, though PragmatIC reckons it takes printing back to its roots. Imprinting is also the process used to stamp out CDs and Blu-Ray disks, and so is known to work within very strict tolerances. PragmatIC reckons it can get down to 100nm objects placed with 10nm accuracy, leading to transistors around a square-micron in size which (PragmatIC claims) is comparable to silicon technologies.

That means chips can be made cheaper, but more importantly they can be laid onto any surface (there's no baking in the PragmatIC process) so electronics can be dropped onto the back of polypropylene labels to create the flashing beer bottle or similar, assuming one can find a battery to power it and an LED to light up.

Batteries aren't much of a problem, companies such as Enfucell and Blue Spark make printed batteries which are only a couple of millimetres thick. LEDs are more of a problem as no one has managed to print them onto a flexible substrate yet, so they have to be inserted and connected in the usual way, even if they're tiny as anything and cheap as chips.

It's that construction process which is getting more expensive, as labour costs rise around the world and silicon-based electronics become as cheap as they're going to be.

Several of those approached for this article talked about the production of electronic toys, and how they peaked in intelligence around a decade ago – with Furby and Sony's Abio being cited as examples. Since then toys have been getting steadily more stupid, not just because they didn't need to be that intelligent but also because the cost of integrating traditional electronics is more than it's worth in sales.

Printed electronics are something of a solution looking for a problem, and doing existing things more cheaply is an attractive justification, but the potential to drop electronic circuits into places they've never been before is much more interesting. Gig tickets which light up at the gate and posters which respond to a tap are both things which can't be done any other way, and indicative of how revolutionary printed electronics will be... eventually. ®

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