Stretchable Energy Harvesting Device based on Thermoelectric Composite Films

Thermoelectric energy harvesting has attracted a lot of attention for powering self-powered devices because of the potential to generate energy anywhere with a temperature difference. In particular, a stretchable thermoelectric generator (S-TEG) can be applied to the repetitively moving parts of a machine and even a human body. Herein, we suggested a S-TEG using thermoelectric composite films made by dispersing n-type Bi₂Te_2.7Se_0.3 powders into the polyvinylidene fluoride elastomer. The prepared n-type thermoelectric composite film with 75 wt% of Bi₂Te_2.7Se_0.3 powders showed a power factor of 1.81 mW m⁻¹ K⁻² at room temperature. Next, we fabricated S-TEG by encapsulating thermoelectric powders-based composite films, and Ag-coated textile electrodes with an Eco-flex matrix. The fabricated stretchable energy harvester generated a maximum output power of 2.35 nW at a temperature difference (ΔT) of 25 K. By repeatedly introducing ΔT=5K, our S-TEG converted the output voltage of 3.4 mV and current signals of 0.25 mA. Moreover, a finite element analysis with multiphysics COMSOL simulation software was conducted to compare the experimental and theoretical thermoelectric output performance of the fabricated S-TEG. Finally, we demonstrated energy harvesting by converting human body heat into electrical energy for potential utilization of our energy harvester. This study led to the development of a S-TEG design using thermoelectric film with a simple and low-cost fabrication procedure, providing a potential approach for use as a next-generation wearable device power source.