Body Heat to Power: Paper-Supported Flexible PANI/GNPs Thermoelectric Films for Sustainable Wearable Electronics

Graphene nanoplatelets (GNPs)-incorporated polyaniline (PANI) composite films with camphor sulfonic acid (CSA) were fabricated on paper substrates using slurry coating followed by hot pressing, leading to a freestanding structure suitable for flexible thermoelectric applications. A detailed investigation that includes morphological, optical, electrical, and thermoelectric studies was carried out to evaluate the performance of the composite films. The incorporation of GNPs increases the conductivity 8-fold to 174 S/cm and the Seebeck coefficient by 19% to 12.7 μV/K for 30 wt % GNPs as optimal loading due to enhanced π-π interactions and energy filtering effect. This leads to a maximum power factor of ∼2.7 μW/mK2 at room temperature. A proof-of-concept device fabricated with 13 strips of the optimized film generates a maximum output voltage and power of ∼3.08 mV and ∼3.54 nW, respectively, under a 30 K temperature difference. A wearable test conducted on the human wrist by using a 14-strips thermoelectric (TE) module reveals that the thermoelectric performance depends on environmental and physiological conditions (blood perfusion, skin thermal resistance, sweat level, contact pressure, etc.) and varies significantly (∼40%) among individuals. However, the TE module is mechanically robust and reliable over 1200 bending cycles.