An electronic device with efficient conductive properties does not always have to be thick and rigid. Scientists from the école polytechnique fédérale de Lausanne (EPFL) were able to develop conductive electronics that is so flexible, it can stretch up to four times its length.

The scientists particularly created a stretchable conductor that is made up of both solid and liquid components. Such was formed by the inclusion of vapor from gallium onto an alloying metal covering.

"This novel approach to deposit and pattern liquid metals enables extremely robust, multilayer and soft circuits, sensors, and actuators," the authors write.

Flexible As Rubber, Thin Yet Efficient

Making elastic electronic circuits has been a big challenge for many scientists because the ingredients used for this are usually stiff.

With this, the EPFL researchers thought of incorporating liquid metal to a thin film in an elastic polymer.

The resulting product is a flexible, rubber-like conductor that can be stretched by up to four times its original length. The material can be pulled in all directions while it does not crack nor lose its conductivity even after a million times of stretching.

The surface tension of the liquid metals used in such experiments are generally high. With this, majority of resulting products are thick in structure. But with the recent creation of the researchers, it may now be possible to make tracks that are thin yet very efficient.

Key Ingredients

The secret key ingredients for the novel conductive electronics are gallium and an alloy of gold.

Co-author Arthur Hirsch explains that gallium has two vital properties: good electrical characteristics and a low melting point of around 30 degrees Celsius. With this, gallium melts easily and remains liquid at room temperature through a process called supercooling.

Gold also has a vital role as it remains homogenous, thus staying intact even if it gets in contact with the polymer – an event that would damage conductivity.

Applications

There is a wide array of applications for this conductive electronics considering it can be used to make circuits that are stretchable and twistable.

Firstly, the conductors may be incorporated in artificial skin prosthesis or robots. Secondly, it may be used in connected clothing fabrics. Lastly, it can also be used to monitor specific biological functions given that it can follow the shape of the human body.

"We can come up with all sorts of uses, in forms that are complex, moving or that change over time," says study author Hadrien Michaud.

The study was published in the journal Advanced Materials on Monday, Feb. 29.