SWCNT/PEDOT:PSS/SA Composite Yarns with High Mechanical Strength and Flexibility via Wet Spinning for Thermoelectric Applications

To fabricate thermoelectric generators (TEGs) with high mechanical strength using single-walled carbon nanotubes (SWCNTs), we combined SWCNTs, poly(3, 4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), and sodium alginate (SA) to synthesize flexible SWCNT/PEDOT:PSS/SA composite yarns via wet spinning. The composite yarns were flexible and dense, with a diameter of approximately 290 µm. Their tensile strength and breaking strain were 151 MPa and 12.7%, respectively, which were approximately 10 and 4 times those of the SWCNT films. However, the thermoelectric properties of the composite yarns were inferior to those of the SWCNT films. The temperature distribution and output voltage of the fabricated TEG with composite yarns were measured at a heater temperature of 100 °C. The temperature difference generated by the TEG with composite yarns was approximately 75% of that generated by the TEG with SWCNT films because the composite yarn had a smaller specific surface area. The output voltage of the TEG with two composite yarns (0.21 mV) was lower than that of the TEG with two SWCNT films. However, arranging the composite yarns at a high density resulted in an output voltage exceeding that for the TEGs with SWCNT films. These findings are highly beneficial for yarn-based TEGs used in wearable sensors.