Synthesis of ultra-stretchable thermoelectric nanofibrous membrane based on wet-electrospun Polyurethane/MWCNTs composites

Abstract

Electrospinning is a versatile method used to create nanofiber membranes with surface-to-volume ratios much higher than those achievable with other film fabrication methods. This technique allows the control of nanofiber morphology, including diameter, shape, and orientation. Such nanostructuring can enhance the thermoelectric performance of composite materials due to quantum confinement and filtering effects. However, the thermoelectric efficiency of a typical electrospun composite is limited due to the insulating nature of the polymer matrix. Therefore, many researchers have combined electrospinning with other techniques or post-treatments to accomplish higher thermoelectric performance. In this study, a new strategy to prepare a stretchable thermoelectric nanofibrous membrane is proposed. The ternary composite of Thermoplastic Polyurethane (TPU)/Multi Wall Carbon Nanotubes (MWCNTs)/Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT: PSS) is obtained by electrospinning of TPU/MWCNTs solution in coagulation bath of PEDOT: PSS water dispersion. The nonsolvent-induced phase separation (NISP) phenomenon, and consequently, the formation of CNTs/PEDOT: PSS/CNTs electrically-conductive chains, were controlled by tuning the concentrations from binary solvents. The optimal value of the Power Factor, 4.28 μW m⁻1 K⁻2, was obtained for 0.12% MWCNTs and a 1:4 ratio of Tetrahydrofuran (THF) to N, N-Dimethylformamide (DMF) in the binary solvent. The sample exhibits a high value of electrical conductivity of 85 S m⁻1 and shows a strain range of 190 %. This study demonstrates the significant potential of the wet-spinning method for producing wearable and sustainable thermoelectric devices, offering an alternative to conventional devices that raise concerns regarding resource scarcity and environmental impact.