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Project Success Stories - Stretchy circuits for fashion and more

Smart clothes that can communicate your feelings or keep tabs on your health where ever you are have shown much promise but faced a major hurdle… they often look and feel like you’re wearing tiny computers. But what if you could have stretchable, breathable, even washable tiny electronic circuit boards? European researchers set out to prove you could.
Project Success Stories - Stretchy circuits for fashion and more
Repellent jackets that really hate water. Pants made of recycled plastic bottles. Moody garments that emote your feelings in colour. These sound pretty weird but science and technology have a way of making everyday things like dressing yourself or lighting your house an 'ambient adventure'.

And so it is with the 'Stretchable electronics for large area applications' (Stella) project, co-funded by the European Commission. Stella has developed new processes, technologies and whole new applications for electronic circuit boards. But the first thing they did was throw out the notion that electronic circuits have to be built onto or into a 'board' - implying something rigid.

The project partners developed stretchable copper boards (SCB) with meandering copper tracks laminated by a soft plastic (thermoplastic polyurethane). This means complex electronic systems can be applied to textiles as simple as a sticker to a T-shirt. What makes it special is a SCB can be used as both a substrate for micro-electronics and integrated in textiles.

To prove it, the Stella partner TU Berlin developed a so-called 'interactive dress', called KLight, using SCB technology which makes integrated lights switch on and off according to body movement.

The dress won the avantex innovative product prize at the 2009 Techtextile exhibition. Commenting on the win, Stella coordinator Dr Christopher Klatt, head of the Physics and Simulation Department at Freudenberg Research said: 'Nowadays, it's not enough to develop fantastic new technologies or to prove their viability in demonstrators. You need to combine an element of glamour and publicity together with professional work on reliability to achieve widespread market acceptance.'

More than glamour

That may be so, but Stella was definitely not all about glamour. It worked primarily on practical and critical applications in the medical and automotive sectors. Here, the developed technologies really tackled today's challenges. For example, the patented Urgo band aid uses Stella's SCBs to monitor the pressure applied in a compression bandage. It is important to get the pressure just right to maximise pain relief and healing, especially for chronic cases and to prevent venous and lymphatic disease. The flexible, comfortable design of Urgo means it can fit neatly together with the bandage to monitor the pressure being applied. It's a groundbreaking little design with high commercial potential. Currently, it is under internal evaluation for new Urgo-like products.

Industry partner Philips Applied Technologies has also put the SCB technology to good use. Together with partners TU-Berlin and Quality Products Int (QPI), it created a stretchable wireless body activity monitor which goes with an adjustable Velcro® strap for ease of fitting. With applications in sports, health care and wellness there is a potentially large market for the product.

'The combination of sensors integrated in a body area network, embedded in stretchable soft-touch materials provides options for enhanced … monitoring and early warning/detection combined with improved wearing comfort,' notes the project on this new development.

Stella has also ventured into new health care areas with a tiny insole device designed with diabetics in mind, a major and growing disease in Europe. Uncontrolled diabetes can cause nerve damage and blood flow problems which can mean the patient no longer feels heat, cold or pain. The muscles in the foot area may also be affected which can lead to walking difficulties, ulcers, gangrene and potential limb loss - about 40,000 foot amputations still occur in Europe each year.

The Stella partners Freudenberg and rubber specialists nora systems developed a three-point foot pressure sensor that fits unobtrusively into the shoe. Because diabetic patients cannot feel the onset of foot problems or pain, Stella's insole monitor detects minute changes for them, including the ageing of the insole itself. Testing has also shown that the SCB can cope with the harsh and sweaty conditions inside shoes.

Babies and cars, too

Stella researchers at IMEC and Verhaert also delved into infant health concerns. An infant respiratory monitor, which is built into light cloth that can be clipped onto pyjamas, measures the baby's chest and abdominal movement more effectively than current technology.

Stella's integrated sensor using the SCB technology looks set to be cheaper, more robust and more sensitive to babies' breathing patterns (recording chest/abdominal elongation) than current state-of-the-art technology.

Stella has also eyed off the huge potential market in intelligent solutions for vehicles. It set up a special demonstrator to prove that it is possible to create bendable electronic circuits suited to car-makers' growing needs for lightweight, energy efficient 'embedded surface heatings'. The team worked on making 2D stretchable polymer circuit boards (SPB) and then forming them into 3D shapes - an action that could destroy traditional circuitry - which fit in, on or under diverse car components.

In their proof-of-concept, the team showed their 3D-shaped circuits were suitable for interior lighting in vehicles; for example, white light-emitting diodes (LED) for reading lights and a blue version as an alarm signal. The technology they developed stood up to harsh testing designed to reflect the real conditions inside vehicles.

'Manufacturing 3D-shaped circuits using well-established 2D processes for flat circuit boards is very attractive for many applications, not only cars,' explains Dr Klatt. 'Inquiries coming from the market give us hope that SPB technology will be used in a lot of marketable products.'

Spin-off and follow-up

So confident that this work has strong market potential, several team members from Fraunhofer IZM have created a spin-off company, called Stretchable Circuits, to 'realise innovative product concepts using stretchable and textile circuit technologies'.

Several Stella partners will also be taking part in a follow-up project called 'Platform for large area conformable electronics by integration' (PLACE-IT). This project planned to establish an industry platform for thin, lightweight and flexible optoelectronics to be used in diverse product designs and on-body applications.

Imagine a lamp that can be designed into any shape or even blended into the surroundings, or curtains that emit light to mimic natural daylight. These sorts of lighting solutions, using energy efficient LEDs and organic LEDs, may soon be possible thanks to flexible substrate technologies developed by European researchers.

'This is a success story and we can be proud of it,' stresses Dr Klatt. 'The demonstrators are ready and the first products are already visible on the horizon.'

The Stella 'Integrated project' received EUR 7 million in EU funding under the 'Information society technologies' (IST) theme of the Sixth Framework Programme for research. The project ended in 2010 but the partners are continuing to disseminate its findings in such events as the Flex-Stretch-Workshop III scheduled for November 2011.

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