Highly stretchable three-dimensional thermoelectric fabrics exploiting woven structure deformability and passivation-induced fiber elasticity

Accommodating localized strains and deformations imposed by human body movements is indispensable to reliable operation of wearable thermoelectric (TE) fabrics. Despite their inherent flexibility and conformability, TE fabrics can suffer from significantly compromised TE performance and mechanical reliability at large applied strains, owing to the limited stretchability of the constituting fibers/components. Here, we propose three-dimensional woven fabrics of high TE performance and exceptional mechanical reliability, encouraged simultaneously by passivation of TE fibers. Immersion-coating in carbon nanotube (CNT) ink effortlessly deposits TE sheath layers on polyurethane (PU) core fibers. PU passivation layers are encapsulated on the coated fibers not only to enhance the intrinsic fiber stretchability by enabling fiber reorientation of individual CNTs, but also to augment the TE properties by regulating heat transfer along PN legs. The passivated fibers are woven into three-dimensional fabrics that harvest heat in the out-of-plane direction with the highest normalized open-circuit voltage of 8.0 mV K −1 and normalized power per leg of 1.1 × 10 −4 μW K −2 among the reported woven-type TE fabrics. The woven structure deformability and the passivation-induced fiber elasticity cooperatively achieve reliable fabric mechanical stability against bending and stretching up to 100% strain. Conforming seamlessly to the curved human forearm, the TE woven fabrics hold promises for efficient body heat harvesting to realize self-powered wearable electronics. • High-performance three-dimensional thermoelectric fabrics of exceptional mechanical reliability against bending and stretching are demonstrated. • Immersion-coating offers a broadly applicable stretegy to facilely prepare thermoelectric fibers by depositing double-walled carbon nanotube (DWCNT) sheath layers on polymeric fibers. • Polyuerethane passivation of the DWCNT-coated fibers simultaneously improves their intrinsic stretchability by allowing for the individual DWCNTs to reorient themselves and enhances thermoelectric performance by regulating heat transfer along DWCNT sheath. • Plain-weaving the passivated fibers achieves the three-dimensional thermoelectric fabrics with the normalized open-circuit voltage of 8.0 mV K −1 and normalized power per leg of 1.1 × 10 −4 μW K −2 , and high stretchability of 100%, enabled by woven structure deformability and passiviation-induced fiber elasticity.