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Thermoelectric generators (TEGs) enable the transformation of human body waste heat into electricity, thus providing a solution to make self-powered wearable electronics. Compared to existing rigid or thin film TEGs made from inorganic thermoelectric materials, two types of 3D all-textile TEG structures were designed in this project. Efforts were made to utilize biocompatible thermoelectric materials, to design flexible and wearable devices, to simplify the fabrication processes and to enhance the performance of the TEG modules. The TEG modules were fabricated either through straightforward hand-stitching or through more scalable sewing with a household sewing machine. By using fabrics as substrate, functional yarns as n-substitute and p-type thermoelectric legs, all-textile flexibility is realized. Similar to classical inorganic TEGs, these two types of all-textile TEGs adopted a common sandwich structure to harvest a temperature difference in the fabric thickness direction, which is the desirable way to collect the heat gradient between human skin and the ambient. To confirm the effectiveness of the hand-stitched TEG and sewing-machine-made TEG designs, several prototypes were fabricated that use PEDOT:PSS coated silk yarn as p-type legs, commercial silver-plated polyamide yarn as a substitute for the n-type legs, washable and stretchable silver paste as electrical connectors and felted wool fabrics as a substrate. At the same time, a method was developed to characterize the axial thermal conductivity of functional yarns. Results show that these two types of designs are successful in generating electricity from the heat gradient in the fabric thickness direction. The output voltage of both designs was on the millivolt level and the maximal output power were on the microwatt level (5.3 cm by 5.3 cm hand-stitched TEG modules) and nanowatt level (21 cm by 12.5 cm by 0.5 cm machine-sewn TEG module). To further improve the TEG module performance to power small electronics in the future, increasing the density of thermoelectric elements and thermoelectric yarns whilst avoiding electrical short-circuiting in the circuitry and applying more thermally and electrically efficient thermoelectric materials are the goals for both types of TEGs. As the sewing-machine-made TEGs are in their initial development stage, there is ample opportunity with regard to modifying the thermoelectric leg arrangements and their conductive connections.