Flexible polyester-embedded thermoelectric device with Bi2Te3 and Te legs for wearable power generation

• A cost-effective flexible thermoelectric generator has been successfully fabricated using electrochemical deposition. This generator is specifically designed for harvesting human body heat and is intended to work near room temperature. It relies on Bi2Te3 and te thermoelectric materials embedded inside a commercial polyester substrate. • Notably, this generator achieves a power density of 0.04 mW·K⁻¹·cm⁻² with only 2 pairs of legs, which is competitive with other flexible thermoelectric generators (TEGs) utilizing Bi2Te3 and Te. Remarkably, it achieves this performance while using only 10 % of the thermoelectric material, thanks to its integration within a flexible matrix. • Due to the way these TEGs are produced, they are scalable for industrial production and exhibit high adaptability, making them ideal for integration into a wide range of wearable devices inside clothes. This study presents an approach for powering wearable sensors by integrating nanostructured bismuth telluride (Bi 2 Te 3 and Te legs) into flexible polyester substrates. The choice of polyester as the substrate is because it is widely used in clothing, especially in items such as shirts, blouses, dresses, and sportswear. This enables seamless integration with wearable devices. By capturing wasted body heat, our small and flexible thermoelectric generators (TEGs) offer long-term operation without the need to plug the batteries. We demonstrate the feasibility of using commercially available polyester for reproducible electrochemical deposition of highly oriented Bi 2 Te 3 and Te material. Through electrodeposition, we embed Bi 2 Te 3 and Te legs within the flexible polyester, creating a cost-effective and easily scalable hybrid system for wearable energy harvesting. Our optimized TEG design, which can be worn on the arm or forehead, achieves impressive power density compared to existing state-of-the-art solutions. With a mere 3.5 °C temperature difference, only two pairs of p- and n-type legs, and a thickness of approximately 15 µm, our TEG generates a maximum open circuit voltage of ∼0.1 mV and a maximum power density of ∼0.04 mW·K -1 ·cm −2 . With 250 pairs, 10 mV can be reached. This cost-effective design also integrates electrical contacts, surpassing previous flexible TEG performances. These advancements make our TEGs suitable for driving microwatt-level electronic sensors and open new avenues for efficient energy harvesting in wearable applications.