Highly surface-conformable thermoelectric patches for efficient thermal contact with arbitrary substrates

Organic thermoelectric (TE) materials are attractive for application as the main or auxiliary power sources of portable and wearable electronic devices. Although utilizing waste heat from practical heat sources (including the human body) remains challenging, this can be solved by developing surface-conformable and body-attachable TE materials. This study introduces a method for preparing multifunctional TE patches to facilitate efficient thermal contact formation between TE patches and various heat sources with flat, curved, wavy, wrinkled, or microstructured surfaces and different textures. The TE patches are prepared using a mixed solution comprising few-walled carbon nanotubes, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), and a commercial gel polymer blend to form freestanding hydrogel nanocomposite films. Under optimized conditions, the composite films exhibit good mechanical (bending and healing) and TE properties and excellent environmental long-term stability. Because the films can form superior thermal contact with arbitrary surfaces, energy can be harvested more efficiently using the conformable TE patches than using the nonconformable patches, suggesting that the potential application range of organic TE materials for future self-powered wearable electronics is not limited to energy harvesting but can be extended to precise temperature sensing.