Flexible, comfortable textiles for high-tech clothing

Researchers at the University of Bayreuth, together with their Chinese colleagues, have developed new nonwoven materials that are electrically conductive as well as flexible and breathable. Their findings have been published in the journal Flexible Electronics.

Today’s electrically conductive clothing can be uncomfortable and rigid, with low air permeability — characteristics which make it awkward for day-to-day use. A more suitable alternative would be bendable and breathable polymer nanofibre nonwovens with electrical conductivity; unfortunately, the limitations of the existing processing techniques have made it difficult to achieve metal-like conductivity in polymer nonwovens.

Professor Dr Andreas Greiner and his team have now overcome this hurdle, succeeding in producing electrically conductive nonwovens which have all the other characteristics one would expect from clothing that is suitable for daily use. The materials are flexible, and thus adapt to movements and changes in posture. In addition, they are air-permeable, meaning they do not interfere with the natural breathing of the skin.

These properties were made possible thanks to the use of a special production process, where in contrast to common methods of production, metal wires were not inserted into finished textiles. Rather, the scientists modified classical electrospinning, which has been used to produce nonwovens for many years: short, electrospun polymer fibres and small amounts of tiny silver wires with a diameter of only 80 nm are mixed in a liquid. Afterwards, they are filtered, dried and briefly heated up. If the composition is right, the resulting nonwoven material exhibits a very high degree of electrical conductivity.

The team’s breakthrough is expected to open up a whole range of possibilities for innovative applications, especially in the area of smart clothes (ie, wearables). Everyday clothing, for example, can be equipped with solar cells such that the captured sunlight is converted to warmth, heating up the textiles themselves. Mobile phones, cameras, mini computers and other wearable electronic devices could be charged by plugging them into the textiles. Sensors installed in the clothes could even provide athletes and trainers with important fitness and health data or could give family and friends information on its location.

“Our approach, which takes the production of conductive textiles as its basis, can in principle be applied to many different systems,” said lead author Steffen Reich, citing current Bayreuth research into microbial fuel cells — which could eventually be used as electrodes in such nonwoven materials. Professor Dr Greiner added that such textiles could “just as easily be installed in … seats and instruments in cars or airplanes”.

Image caption: Steffen Reich, doctoral student at the University of Bayreuth, producing a dispersion with tiny silver wires. Image credit: Christian Wißler.