LONDON An IMEC laboratory at the University of Ghent in Belgium has realized interconnections for elastic electronic wires that can be stretched to twice their original length while maintaining electrical conductivity. The technology could be significant in such applications as foldable displays, biomedical applications and textiles that incorporate electronics, according to research organization IMEC (Leuven, Belgium).
Electronic circuits that are flexible and elastic could be used to enhance user comfort. Bladder implants for treating incontinency, brain electrodes that treat epilepsy and depression, fall-detection monitors for the elderly or intelligent textiles that monitor health conditions are coming up thanks to technological enhancements in flexible electronics.
IMECís associated laboratory at Ghent University has produced a 3-cm elastic interconnection system by embedding 4-micron width gold wires in an elastic silicone film. A horseshoe shaped wire was used which significantly reduced the stress in the wire compared with an elliptical shape while maintaining the initial electrical resistance. To further increase the stretchability without limiting the electrical performance, the interconnection wire was divided into four parallel tracks. The wires were coated with a 2-micron thick nickel layer for soldering wires to the ends.
Interconnection wires were fabricated with different angles of the horseshoe shape and tested by stretching them in the longitudinal direction to the point of electrical failure. The electrical failure was caused by a rupture in the metallic track. However, all interconnections - even those that experienced electrical failure - recovered their conductance when they returned to their normal length. The best connector stretched from 3 to 6 centimeters without losing conductance.
The group is developing technology that would allow the incorporation of the elastic interconnections within full electronic circuits. This goal is being pursued by three projects: BioFlex (Biocompatible Flexible Electronic Circuits) with funding by the Institute for the Promotion of Innovation by Science and Technology in Flanders; STELLA (Stretchable Electronics for Large Area Applications) with funding by the European Commission; and SWEET (Stretchable and Washable Electronics for Embedding in Textiles) with funding by the Belgian Science Policy.
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