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 in Sweden, now presents a thread made of conductive cellulose, which offers fascinating and practical possibilities for electronic textiles.
Miniature, wearable electronic gadgets 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. The research is now published in ASC Applied Materials & Interfaces.
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.
The cellulose thread could lead to garments with built-in electronic, smart functions, made from non-toxic, renewable and natural materials. 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 fibers 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,” explained professor Christian Müller, the 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 center Wallenberg Wood Science Center, in cooperation with colleagues in Sweden, Finland and South Korea.
The electrically conductive yarn is produced in a “layer-on-layer” coating process with an ink based on the biocompatible polymer polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: PSS). The e-textile thread developed by the researchers measures a record-high conductivity for cellulose thread in relation to volume of 36 S/cm-, which can be increased to 181 S/cm by adding silver nanowires. The thread coated with PEDOT: PSS can handle at least five machine washes without losing its conductivity. By integrating the cellulose yarn into an electrochemical transistor, the researchers have also been able to demonstrate its electrochemical function.
Throughout human history, textiles have been made from natural fiber and cellulose. But since the middle of the 20th century, synthetic fibers have become more common in our clothing, particularly in the fashion industry. With the greater focus and awareness now on sustainable alternatives, interest in natural fibers and textiles is returning and growing. Large Swedish chains such as H&M and Lindex have set high goals for increasing the proportion of garments produced from more sustainable materials.
Sozan Darabi, Michael Hummel, Sami Rantasalo, Marja Rissanen, Ingrid Öberg Månsson, Haike Hilke, Byungil Hwang, Mikael Skrifvars, Mahiar M. Hamedi, Anja Lund, and Christian Müller. Green Conducting Cellulose Yarns for Machine-Sewn Electronic Textiles. ACS Appl. Mater. Interfaces 2020, 12, 50, 56403–56412