Imec collaboration places displays on clothing fabrics

September 03, 2015 // By Graham Prophet
Researchers from Holst Centre (Eindhoven, the Netherlands) (set up by TNO and imec), imec (Leuven, Belgium) and CMST, imec’s associated lab at Ghent University, have demonstrated the world’s first stretchable and conformable thin-film transistor (TFT) driven LED display laminated into textiles.

The work paves the way, say the researchers, to wearable displays in clothing providing users with feedback. Wearable devices such as healthcare monitors and activity trackers are now a part of everyday life for many people. Today’s wearables are separate devices that users must remember to wear. The next step forward, this team believes, will be to integrate these devices into our clothing. Doing so will make wearable devices less obtrusive and more comfortable, encouraging people to use them more regularly and, hence, increasing the quality of data collected. A key step towards realising wearable devices in clothing is creating displays that can be integrated into textiles to allow interaction with the wearer.

“ maximise the benefits wearables can offer, they need to be able to provide feedback on what users are doing as well as measuring it. By combining imec’s stretch technology with our expertise in active-matrix backplanes and integrating electronics into fabrics, we’ve taken a giant step towards that possibility,” says Edsger Smits, Senior research scientist at Holst Centre.

The conformable display is very thin and mechanically stretchable. A fine-grain version of the proven meander interconnect technology was developed by the CMST lab at Ghent University and Holst Centre to link standard (rigid) LEDs into a flexible and stretchable display. The LED displays are fabricated on a polyimide substrate and encapsulated in rubber, allowing the displays to be laminated in to textiles that can be washed. Importantly, the technology uses fabrication steps that are established in the manufacturing industry, enabling rapid industrialisation.

Smaller LEDs are now mounted on an amorphous indium-gallium-zinc oxide (a-IGZO) TFT backplane that employs a two-transistor and one capacitor (2T-1C) pixel engine to drive the LEDs. These second-generation displays offer higher pitch and increased, average brightness. The generation now being presented is shown as a 32 x 32 pixel demonstrator with a resolution of 13 pixels per inch (ppi) and average brightness above 200 candelas