3D Helical Flexible Thermoelectric Film Generator Based on BiTe/PEDOT: PSS/PU/MWCNT.

With the ever-growing development of miniature electronics, self-charging technology is highly essential, and wearable thermoelectric (TE) microgenerators are up to this task. However, the currently existing TE materials and device structures seldom achieve both high flexibility and output properties simultaneously. This study presents an advanced strategy for fabricating flexible TE films and highly stretchable three-dimensional (3D) thermoelectric generator (TEG) devices. A scalable approach was employed to construct foldable TE films and helical-structured devices with exceptional stretchability and thermal management capabilities, enabling open-air channels to maintain temperature gradients without external heatsinks. By optimizing the composition of BiTe, PEDOT: PSS, multiwalled carbon nanotubes (MWCNTs), and polyurethane (PU), a balance between TE performance and wearability was achieved. The composite film demonstrated mechanical endurance─resistance change ratios below 3% after 1,500 bending cycles (4 mm radius). The 3D helical TEG device exhibited remarkable stability with only a 6% voltage reduction and a 0.7% resistance increase under a 20% strain. Even at a minimal Δ of ∼3 K, the device retained a stable output voltage of 1.3 mV, highlighting its practicality for low-grade heat harvesting. This work provides an effective way to develop wearable TEG devices and opens a meaningful dialogue on structural innovation for wearable energy harvesting.