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 threedimensional 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 threedimensional 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 x 10(-4) mu W 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.

Automated summary

A method of achieving high thermoelectric performance and exceptional mechanical reliability of three-dimensional fabrics is proposed, which involves passivation and weaving of thermoelectric fibers. The woven fabric can harvest heat in the vertical direction and has high open-circuit voltage and power, as well as reliable mechanical stability. This new fabric holds promise for self-powered wearable electronics.