Close-knit conductor

Video: Fabric circuits pave the way for wearable tech

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Smart clothes promise to weave technology into everyday garments – but what do you do when they get dirty?

In-fabric wiring that cannot cope with the moisture, heat and stresses of a wash-and-spin cycle is no good to anyone. But now a team at the Institute of Textiles and Clothing in Hong Kong, China, has hit on a highly stretchable fabric formulation that can withstand multiple machine washes.


What Xiao-Ming Tao and her colleagues have engineered is a textile so shot through with electrical wiring that they call it a fabric circuit board (FCB). Microchips and other components can be incorporated into it, and they remain connected when flexed.

The material comprises multiple filaments of pre-stretched elastic yarn and polyurethane-coated copper fibres. They are combined using a computerised knitting machine (see picture, above right).

In regular wear and tear, the team’s tests show the material can be stretched by 20 per cent about a million times before any of the fibres fail. And like a regular circuit board, Tao says, the fabric can be used in multiple layers thanks to the polyurethane insulation surrounding the copper. Currents can be carried just like in regular circuit boards.

Military app

Among other uses, the team has shown how its fabric can be built into a soldier’s bulletproof Kevlar vest (see video, above). If the wearer is shot, the material can sense the bullet’s impact and send radio a message back to a base.

But it is washability that is most vital for mass consumer use – and after multiple cycles in a Whirlpool washing machine they found no problems with deformation or electrical resistance until the material had undergone at least than 30 washes at 40 °C and drying at 75 °C.

Such performance could be what smart clothing advocates have been waiting for, says Lucy Dunne, a wearable technology expert at the University of Minnesota in St Paul. “Washability is a big plus for e-textile circuits, as is durability of the embedded conductors,” she says. “And as stretchable fabrics are increasingly common in everyday clothing, a conductor that isn’t affected by stretching will improve both comfort and aesthetics.”

And Dunne thinks demonstrating the technology’s use in a bulletproof vest is impressive. “The ballistic application is pretty neat.”

Journal Reference: Proceedings of the Royal Society A, doi.org/vgz