Scalable fabrication of flexible thermoelectric generator with non-toxic Ga:ZnO and PEDOT:PSS thermoelements for wearable energy harvesting

This study presents a lightweight, flexible thermoelectric generator (TEG) designed for sustainable energy harvesting in wearable electronics. The TEG integrates p-type PEDOT:PSS and n-type Ga:ZnO thermoelements, utilizing scalable drop-casting and 3D-printing techniques to address key concerns of sustainability, scalability, and safety. Unlike conventional TEGs that rely on toxic or rare-earth materials, this device employs predominantly earth-abundant, non-toxic components, offering a more cost-effective and environmentally friendly alternative. Structural analysis using FE-SEM and EDX revealed a relatively dense microstructure with uniform elemental distribution in the free-standing thermoelements, contributing to the device's mechanical flexibility and performance stability. The TEG, consisting of five thermoelement pairs, achieved a peak open-circuit voltage of 0.111 mV and a power output of 0.123 nW at a temperature difference (ΔT) of 10 K, demonstrating performance competitive with TEGs fabricated using more complex and expensive methods. When tested on a human wrist, the TEG generated 0.230 nW at a ΔT of 17 K, outperforming other wearable TEGs, with power increases observed during body movement. Additionally, the device maintained stable resistance at a 90° bending angle, enhancing its ability to conform to the body's shape for improved energy harvesting and efficiency. While the power output can be further improved, this TEG represents a notable advancement in flexibility, scalability, and the use of eco-friendly, cost-effective materials and fabrication methods. Addressing these critical challenges in wearable thermoelectrics paves the way for future self-powered health monitoring, fitness tracking, and environmental sensing applications.