STUDY FINDS
Forget to bring your charger with you on vacation? What if your clothing could generate electricity from the heat your body naturally produces? This futuristic concept is now approaching reality thanks to scientists at Chalmers University of Technology in Sweden and Linköping University.
Researchers say the remarkable new textile technology converts body heat into electricity through thermoelectric effects, potentially powering wearable devices from your clothing. The innovation, described in an Advanced Science paper, centers on a newly developed polymer called poly(benzodifurandione), or PBFDO, which serves as a coating for ordinary silk yarn.
“The polymers that we use are bendable, lightweight and are easy to use in both liquid and solid form. They are also non-toxic,” says study first author Mariavittoria Craighero, a doctoral student at the Department of Chemistry and Chemical Engineering at Chalmers, in a statement.
Unlike previous attempts at creating thermoelectric textiles, this breakthrough addresses a critical barrier that has long hampered progress: the lack of air-stable n-type polymers. These materials are characterized by their ability to move negative charges and are essential counterparts to the more common p-type polymers in creating efficient thermoelectric devices.
“We found the missing piece of the puzzle to make an optimal thread – a type of polymer that had recently been discovered. It has outstanding performance stability in contact with air, while at the same time having a very good ability to conduct electricity. By using polymers, we don’t need any rare earth metals, which are common in electronics,” explains Craighero.
Thermoelectric generators work by converting temperature differences into electrical energy. When one side of a thermoelectric material is warmer than the other, electrons move from the hot side to the cold side, generating an electrical current. The human body continuously generates heat, creating natural temperature gradients between the skin and the surrounding environment.
For efficient thermoelectric generation, both p-type (positive) and n-type (negative) materials must work together. While p-type materials have been well-established in previous research, creating stable n-type materials has been a persistent challenge. Most n-type organic materials degrade rapidly when exposed to oxygen in the air, often becoming ineffective within days.
What makes this development particularly exciting is the remarkable stability of PBFDO-coated silk. Unlike similar materials that degrade within days when exposed to air, these new thermoelectric yarns maintain their performance for over 14 months under normal conditions without any protective coating. The researchers project a half-life of 3.2 years for these materials – an unprecedented achievement for this type of organic conductor.
Beyond electrical performance, the mechanical properties of the PBFDO-coated silk are equally impressive. The coated yarn can stretch up to 14% before breaking and, more importantly for everyday use, it can withstand machine washing.
“After seven washes, the thread retained two-thirds of its conducting properties. This is a very good result, although it needs to be improved significantly before it becomes commercially interesting,” states Craighero.
The material also demonstrates remarkable temperature resilience. During testing, the researchers found that PBFDO remains flexible even when cooled with liquid nitrogen to extremely low temperatures. This exceptional mechanical stability allows the material to withstand various environmental conditions and physical stresses that would be encountered in real-world use.
To showcase the technology’s potential, the research team created two different thermoelectric textile devices: a thermoelectric button and a larger textile generator with multiple thermoelectric legs.
The thermoelectric button demonstrated an output of about 6 millivolts at a temperature difference of 30 degrees Celsius. Meanwhile, the larger textile generator achieved an open-circuit voltage of 17 millivolts at a temperature difference of 70 degrees Celsius.
With a voltage converter, this could help power ultra-low-energy devices, such as certain types of sensors. However, the current power output—0.67 microWatts at a 70-degree temperature difference—is far below what would be required for USB charging of standard electronics.
While these power outputs mark a major step forward in thermoelectric textiles, it’s important to note that the temperature differences used in lab tests—up to 70 degrees Celsius—are significantly higher than what would typically be experienced in everyday clothing. This means real-world performance may be lower than laboratory results suggest.
Despite current limitations in power output, the technology shows particular promise for healthcare applications. Small sensors that monitor vital signs like heart rate, body temperature, or movement patterns could potentially operate using this technology, eliminating the need for battery changes or recharging.
For patients with chronic conditions requiring continuous monitoring, self-powered sensors embedded in clothing could provide valuable data without the hassle of managing battery life. Similarly, fitness enthusiasts could benefit from wearables that never need charging, seamlessly tracking performance metrics during activities…
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