Stretchable continuous p-n alternating thermoelectric fibers for energy harvesting and sensing devices

The increased human demand for an intelligent life puts forward a great requirement for lightweight, stretchable, and comfort sensing and energy harvesting devices. Stretchable thermoelectric fiber becomes very attractive due to it can directly convert human body waste heat into electricity and enables stress, strain, and temperature sensing by designing the structure of the materials. However, the preparation of stretchable poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fibers with enhanced performances and continuous p-n alternating structure remains a challenge. In this study, the stretchable continuous p-n alternating thermoelectric fibers were prepared by a simple and controllable microfluidic wet-spinning process, in which the single-walled carbon nanotubes (SWCNT)/PEDOT:PSS/polyurethane (PU) and polyethyleneimine (PEI) doped SWCNT/PEDOT:PSS/PU were used as p- and n-type segments, respectively. To optimize the performances, the effect of SWCNT and PEI concentration on the morphology, thermoelectric, and mechanical properties of p- and n-type fibers were analyzed. The power factor of the p- and n-type fibers were 2.67 and 3.48 µW m⁻¹ K⁻²_, respectively, with a stress of 16 ~ 19 MPa and strain of 70%. Then, the strain and temperature sensors were constructed by the stretchable TE fibers and used for respiration and motion monitoring, showing excellent sensitivity and stability. All the results demonstrate the multifunctions of the stretchable TE fibers used as flexible wearable electronics.