An illuminating yarn

A team from Manchester University’s William Lee Innovation Centre (WLIC) has developed prototype electroluminescent textile yarns that illuminate clothing in the dark.

Currently, high visibility products such as those worn by cyclists depend on external light sources to make them visible.

They can be ineffective in low light situations and require a strong light source from car headlights or street lighting to make them visible.

The latest WLIC development, made from electroluminescent (EL) yarns, allows the wearer to be permanently visible.

EL yarn emits light when it receives electrical power and its development has been based on thin film electroluminescent technology.

The yarn consists of an inner conductive core yarn, coated with electroluminescent ink and a protective transparent encapsulation, with an outer conductive yarn wrapped around it.

When the EL yarn is powered with an inverter the resultant electrical field between the inner and outer conductor causes the electroluminescent coating to emit light. The emission of light occurs between the contact points between the outer yarn and the inner yarn.

Dr Tilak Dias, head of the WLIC, said: ‘At the moment the EL yarn we have developed is less flexible than conventional yarns. But it is more flexible than current optical fibres that are incorporated within fabrics to provide illumination.

‘EL yarn can be easily incorporated into a knitted or woven fabric and the resultant active illuminating fabric provides illumination when it is powered.

‘The luminance of a single strand of the EL yarn is greater than that of photoluminescent glow yarns, which are currently used in some high visibility applications.

‘Weaving or knitting the yarn in a particular manner, so that more yarn per unit area is achieved, improves the luminance of the EL yarn.’

The prototype yarn currently receives its power from a mains electricity supply but a spokesman at Manchester University said EL would be powered by a battery once it becomes commercially available.