To make wearables truly effortless — integrating seamlessly into daily life virtually unnoticed — engineers must solve a few essential problems. These include eliminating bulky hardware and enhancing comfort while maintaining durability. Eliminating the need to charge a battery — and possibly eliminating the battery itself — is a critical step on the road to next-level wearable technology. One solution holds promise for each of these concerns: electronic textiles.

E-textiles haven’t quite found their stride yet, but researchers from around the world are getting into the game. One visionary team of Nordic researchers sees electronic textiles playing another significant role: as a key element in the widespread adoption of ecologically sustainable technology. Current wearables, useful as they may be, still require rare metals and other unsustainable materials. Wearables, like most devices, also contribute to increasingly massive amounts of global electronic waste.

Seeking an all-in-one solution for a conductive yet eco-friendly fiber, researchers from Chalmers University of Technology in Sweden and Aalto University in Finland looked to the past rather than the future. Synthetic fibers, first introduced in the mid-twentieth century, remain popular for many modern garments. But for most of human history, clothing was made exclusively from natural materials, including cellulose fibers from plants.

While it’s possible to produce flax, linen, and cotton sustainably, the Aalto University group previously developed a composite cellulose fiber known as Ioncell. Made from recycled clothing, newspapers, and other cellulose products, Ioncell offers a zero-waste option for textiles in general.

Using Ioncell fibers, a polymeric dye, and silver nanowires, the research team made an electronically conductive thread. Sewn into a fabric using a standard consumer sewing machine, the thread successfully transformed body heat into a micro-level electric current.

If made into a full garment, the thread could harvest body heat to power miniature sensors and transmitters built into the fabric without needing a battery or charging apparatus. Test results showed that a body temperature of 37C/98.6F consistently generated roughly 0.2 microwatts of electricity. The cellulose also remained conductive after several machine washings. The team recently published their findings in the journal ASC Applied Materials & Interfaces.

Electronic textiles used in healthcare could revolutionize the capabilities of wearables. Remote patient monitoring, health tracking, and responsive textiles that adjust for changing biodynamics have applications in the diagnosis, treatment, and management of countless conditions. For the individual, smart textiles could provide deep insight into personal health and fitness with minimal daily effort. When it comes to eco-responsibility, the benefits of conductive cellulose thread may have a significant, worldwide impact.