Electronic textiles offer revolutionary new opportunities in various fields in particular healthcare. But to be sustainable, they need to be made of renewable materials.
A research team led by Chalmers University of Technology, Sweden, now presents a thread made of conductive cellulose, which offers fascinating and practical possibilities for electronic textiles.
"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," explained Sozan Darabi, doctoral student at the Department of Chemistry and Chemical Engineering at Chalmers University of Technology.
Darabi, together with Anja Lund, a researcher in the same group, has been working with electrically conductive fibres for electronic textiles for several years. Previously, the group focused on silk, but now discoveries have been taken further through the use of cellulose.
Built-in electronics in non-toxic, renewable, and natural materials
The results now presented by the researchers show how cellulose thread offers huge potential as a material for electronic textiles and can be used in many different ways.
Sewing the electrically conductive cellulose threads into a fabric using a standard household sewing machine, the researchers have now 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 degrees Celsius, the textile can generate around 0.2 microwatts of electricity.
"This cellulose thread could lead to garments with built-in electronic, smart functions, made from non-toxic, renewable and natural materials," said Darabi.
The production process for the cellulose thread has been developed by co-authors from Aalto University in Finland. 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
The benefits of e-textiles and cellulose
Electronic textiles could improve our lives in several ways. One important area is healthcare, 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.
"Cellulose is a fantastic material that can be sustainably extracted and recycled, and we will see it used more and more in the future. 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," said Christian Müller, research leader for the study and a professor at the Department of Chemistry and Chemical Engineering at Chalmers University of Technology.
This work of the research team from Chalmers is performed within the national research centre Wallenberg Wood Science Centre, in cooperation with colleagues in Sweden, Finland and South Korea.