Imagine a sweater that charges your phone or powers health-monitoring devices while you go about your day.
Scientists at Chalmers University of Technology in Sweden have made strides toward this idea with a special silk thread coated in a conductive plastic.
This new material could pave the way for clothes that generate electricity, bringing wearable technology to the next level.
The concept is based on thermoelectric textiles, which create power from temperature differences.
For example, your body heat could generate electricity when it contrasts with cooler outside air.
This electricity could power sensors that monitor heart rate or movement, without needing batteries. But making such a fabric is challenging; it requires materials that are both safe to wear and able to conduct electricity efficiently.
In this study, researchers coated a silk thread with a conducting polymer—a type of plastic that can carry an electric current.
“The polymers we use are bendable, lightweight, and non-toxic,” said Mariavittoria Craighero, a Ph.D. student involved in the project. This polymer makes the thread both flexible and suitable for textiles, as it’s safe for contact with the body.
The process used to make this silk thread is similar to previous methods, but with important improvements. Previously, metals were used in the thread to maintain stability in air.
Now, with the discovery of a new polymer, researchers achieved a stable, air-friendly thread that conducts electricity without the need for metals. This advancement means fewer rare materials are needed, which is more sustainable and avoids using rare-earth elements.
To test their silk thread’s potential, the researchers created two simple thermoelectric generators: a button made with the conductive thread and a piece of fabric with the thread sewn in.
When placed between a hot and cold surface, the fabric generated a small voltage that could potentially be used to charge electronics through a USB. For instance, a 30-degree Celsius difference in temperature created about 6 millivolts in a piece of fabric. While small, this amount could be boosted with a voltage converter to charge portable devices.
Durability is another key factor. The team found that the thread still worked well after a year and stayed conductive after seven washes, retaining about two-thirds of its power. Although this performance needs further improvement for everyday use, it’s a promising start.
At this stage, making the thread and sewing it into fabric takes time and must be done by hand. For example, creating the fabric used in their tests took four days of needlework. However, the researchers believe that automated production could be developed to make this technology available on a larger scale.
“We’ve shown that it’s possible to create conductive materials that meet the demands of wearable technology,” said Christian Müller, a professor at Chalmers and the project leader. The potential of thermoelectric textiles is significant, and this breakthrough could open the door to smart fabrics that benefit society in new ways.
