A silk thread that can turn clothes into chargers

Oct. 31 () –

An ordinary silk thread, covered with a conductive plastic materialhas shown promising properties for converting textiles into electricity chargers.

This advance has been presented by a research group, led by Chalmers University of Technology in Sweden, in the journal Advanced Science.

Thermoelectric textiles convert temperature differences, for example between our body and the air around us, into an electrical potential. This technology can be very useful in our daily lives and in society. Connected to a sensor, textiles can power these devices without the need for batteries. These sensors can be used to monitor our movements or measure our heart rate.

Since textiles must be worn close to the body, the materials used in them must meet high demands for safety and flexibility. The silk thread the researchers tested has a coating of a conductive polymer. It is a plastic material with a chemical structure that makes the material electrically conductive and adapts well to textiles.

“The polymers we use are flexible, light and easy to use in both liquid and solid form. In addition, they are non-toxic,” he says. in a communicationo Mariavittoria Craighero, PhD student in the Department of Chemistry and Chemical Engineering at Chalmers University of Technology and first author of a recently published study.

The method used to manufacture the electrically conductive thread is the same as that used in previous studies within the same research project. Previously, the thread contained metals to maintain its stability in contact with air. Since then, advances have been made to make the thread only from organic (carbon-based) polymers. In the current study, researchers have developed a new type of thread with improved electrical conductivity and stability.

“We have found the missing piece of the puzzle to make an optimal thread: a type of polymer that had been recently discovered. It has exceptional performance stability in contact with air, while at the same time having a very good ability to conduct electricity. electricity. By using polymers, we do not need any rare earth metals, which are common in electronics“says Craighero.

To demonstrate how the new thread can be used in practice, the researchers made two thermoelectric generators: a button sewn with the thread and a piece of fabric with threads sewn onto it. When they placed the thermoelectric fabrics between a hot and a cold surface, they were able to observe the tension in the measuring instrument increase. The effect depended on the temperature difference and the amount of conductive material in the fabric.

As an example, the largest piece of cloth showed around 6 millivolts at a temperature difference of 30 degrees Celsius. In combination with a voltage converter, it could theoretically be used to charge portable electronic devices via a USB connector. The researchers have also been able to show that the yarn’s performance is maintained for at least a year. It is also machine washable.

“After seven washes, the yarn retains two-thirds of its conductive properties. It is a very good result, although it needs to be improved significantly before it is commercially interesting,” says Craighero.

It can fulfill functions that these textiles require. Today, thermoelectric fabric and button cannot be produced efficiently outside of the laboratory environment. The material must be made and sewn by hand, which is time-consuming. Just sewing it into the fabric shown required four days of sewing. But the researchers see that the new thread has great potential and that it would be possible to develop an automated process and scale it up.

“We have now shown that it is possible to produce conductive organic materials that can fulfill the functions and properties that these textiles require. This is an important step forward. There are fantastic opportunities in thermoelectric textiles and this research can be of great benefit to society” says Christian Müller, professor at the Department of Chemistry and Chemical Engineering at Chalmers University of Technology and research leader of the study.