Direct Ink Writing of Stretchable Organic Thermoelectrics

Wearable thermoelectrics (TEs) have recently received increasing attention for their potential to harvest electricity from the skin heat. However, the unconventional form factor of wearable devices (stretchable and large-area) and the bulk nature of TEs call for new processing techniques that exploit the third dimension. Here we propose the direct int writing (DIW) of PEDOT:PSS, one of the best reported organic TE materials, directly on a stretchable substrate. We introduce an extremely easy route to formulate a PEDOT:PSS hydrogel with the right rheology for DIW. DIW allowed the creation of intricate 3-dimensional shapes that when dried, provided a competitive power factor. Moreover, in wet state, the DIW patterns are flexible, and when combined with a stretchable substrate, led to stretchable TE devices that retain conductivity up to 15% strain. This work holds significant promise for the future development of soft and wearable electronics, in which stretchability and design flexibility are crucial features.