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Breakthrough in wearable LED displays heralds IoT feedback

Wed 2 Sep 2015

Wearable LED display on woman's leg

Researchers in Holland have announced a revolutionary wearable LED display which they claim opens up the possibility for IoT devices such as medical monitors and health trackers to emerge from their GUI-less opacity and provide real-time visual feedback in the context of the wearer – as well as offering new possibilities for in-car displays.

The new paper follows up on the debut for the display at the 15th International Meeting on Information Display in Korea last month, and details the creation of stretchable 45×80 RGB LED conformable display material embedded within polyurethane film. The device runs with a 3mm pitch between the pixels, an operating voltage of 5V, brightness above 30cd/m and ductility of up to 10%.

The paper notes: “A stretchable and conformable display which can be stretched and bent into any direction provides new opportunities since it can conform to complex surfaces and locally stretch where needed. The fabrication of stretchable and conformable display technologies is a missing link towards realizing the next generation applications such as wearable displays in/on textiles and digital signage currently achieved by projector mapping. It could as well provide new opportunities to the automotive industry where displays could be integrated on the A-pillars, the steering wheel, dashboard and even in the car seats.”

Like chain-mail the device is comprised of rigid islands of electronic functionality meshed together with ductile interconnecting material, a process formerly used to demonstrate prototypes for an RSI wrist-band and a baby jaundice photo-therapy blanket.

The circuitry behind the display is first elaborately created over polyimide film, with strata of circuitry prepared by laser ablation before insertion of the LEDs, which need to be placed with conductive adhesives due to the requirements for low-temperature assembly.

The researchers have to contend with two possible base approaches to flexible LED displays, one involving the casting or injection moulding of polydimethylsiloxane (PDMS) elastomer, and the other employing thermoplastic polyurethane (TPU). Though the latter provides less ductility and is less stable in terms of chemical and thermal resilience, it was chosen for its lower costs and potential facility of production.

The race towards flexible displays, however, seems likely to go to the tortoise rather than the hare, due to issues of power supply and physical resilience. Even in 2010 there were comments about how frequently proof-of-concept flexible displays turn up at trade shows yet never materialise into actual products.

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