Flexible electronics, also known as flex circuits or flex circuit boards, represent a technology for building electronic circuits by depositing electronic devices on flexible substrates such as plastic or even organic materials.

A new generation of flexible circuit connectors could produce a new class of electronic applications, such as stretchable thermometers, biomedical devices and electronic clothing, all possessing the main advantage of being flexible and washable.

Jan Vanfleteren, Dominique Brosteaux, Eva De Leersnyder, Frederick Bossuyt, Fabrice Axisa and Mario Gonzalez of the Interuniversity Microelectronics Centre and Ghent University in Belgium have developed these new elastic interconnectors that can double their initial length when stretched. "For biomedical and textile applications, the comfort of the user will be enhanced if the electronic circuits are not only flexible, but also elastic," the researchers explained in their study. "Biomedical applications include implantable devices and electronics on skin."

The 3-centimeters-long connectors are produced by embedding 4-microns-thick gold wires in a silicone film that already displayed remarkable elastic properties. They were then coated with a 2-microns-thick layer of nickel used to solder them to the ends. "Besides this construction, our team has also been developing alternative versions of this technology based on the same molded interconnect device (MID) technology," said Vanfleteren. MID stands for Moulded Interconnected Devices, a technique that can be used to combine the mechanical and electrical functions on a single unit, which could easily replace current circuit boards.

As a first result, they were able to create a stretchable thermometer that can be wrapped around the forehead of a patient and is flexible enough to adapt to the contour of the head and stick to it.

This is only one of the many potential applications envisioned by the researchers, the next step being to incorporate these elastic interconnectors into full electronic circuits.