Cellulose thread enables electronic textiles

Electronic textiles offer revolutionary new opportunities in various fields, but in order to be sustainable, they need to be made of renewable materials. A research team led by Chalmers University of Technology now presents a thread made of conductive cellulose, which offers fascinating and practical possibilities for electronic textiles.

As explained by Chalmers doctoral student Sozan Darabi, “Miniature, wearable, electronic gadgets are ever more common in our daily lives. But currently, they are often dependent on rare, or in some cases toxic, materials. They are also leading to a gradual build-up of great mountains of electronic waste. There is a real need for organic, renewable materials for use in electronic textiles.”

Together with Chalmers researcher Anja Lund, Darabi had been working with electrically conductive fibres for electronic textiles for several years. The focus was previously on silk, but now the researchers have revealed in the journal ASC Applied Materials & Interfaces how cellulose thread offers huge potential for many different applications.

Sewing the electrically conductive cellulose threads into a fabric using a standard household sewing machine, the researchers succeeded in producing a thermoelectric textile that produces a small amount of electricity when it is heated on one side — for example, by a person’s body heat. At a temperature difference of 37°C, the textile can generate around 0.2 mW of electricity.

The dark yarn is the cellulose yarn and the lighter one is a commercially available silver-plated yarn, both of which are electrically conductive. Photographer: Anna-Lena Lundqvist/Chalmers University of Technology.

“This cellulose thread could lead to garments with built-in electronic, smart functions, made from non-toxic, renewable and natural materials,” Darabi said.

The production process for the cellulose thread was developed by study co-authors from Aalto University. In a subsequent process, the Chalmers researchers made the thread conductive by dyeing it with an electrically conductive polymeric material. The researchers’ measurements show that the dyeing process gives the cellulose thread a record-high conductivity — which can be increased even further through the addition of silver nanowires. In tests, the conductivity was maintained after several washes.

Close-up of the conductive cellulose thread. Photographer: Anna-Lena Lundqvist/Chalmers University of Technology.

Electronic textiles could improve our lives in several ways. One important area is health care, where functions such as regulating, monitoring and measuring various health metrics could be hugely beneficial.

In the wider textile industry, where conversion to sustainable raw materials is a vital ongoing question, natural materials and fibres have become an increasingly common choice to replace synthetics. Electrically conductive cellulose threads could have a significant role to play here too, the researchers say.

“Cellulose is a fantastic material that can be sustainably extracted and recycled, and we will see it used more and more in the future,” said Chalmers Professor Christian Müller, research leader on the study. “And when products are made of uniform material, or as few materials as possible, the recycling process becomes much easier and more effective. This is another perspective from which cellulose thread is very promising for the development of e-textiles.”

Top image: Sewing thermoelectronics into regular textile. Photographer: Anna-Lena Lundqvist/Chalmers University of Technology.

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