All-3D-Printed PEDOT:PSS-Based Stretchable Thermoelectric Devices for Power Generation

The development of flexible thermoelectric devices (F-TEDs) for wearable electronics has gained significant attention due to their potential for sustainable energy harvesting. However, the practical use of flexible thermoelectric materials is limited by their stretchability and the complexities of device integration, particularly with regard to mechanical performance and fabrication. To address these issues, we developed a stretchable polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based thermoelectric composite and an all three-dimensional (3D) printing fabrication method, overcoming mechanical and manufacturing challenges to enable seamless integration in wearable electronics. The composite demonstrates superior tensile strength and stretchability, making it ideal for applications requiring both flexibility and robustness while retaining its thermoelectric properties. To enable precise and scalable device fabrication, we designed an ink with excellent viscoelasticity optimized for 3D printing. This ink allows for high-resolution, multimaterial patterning, facilitating the construction of intricate device structures through an all 3D printing approach. The combination of optimized ink formulation and all 3D printing technologies results in the fabrication of fully integrated stretchable thermoelectric devices with remarkable mechanical and electrical stability. At a temperature gradient of 40 K, the all-3D-printed PEDOT:PSS-based S-TEDs produce an open voltage of about 3.18 mV and a power density of about 6.78 nW cm^-2. The fabricated devices exhibit stable thermoelectric performance under strains exceeding 50%, retaining over 90% of their output after 2000 stretching cycles. Furthermore, they demonstrate the capability to continuously power an LED under dynamic body motions, such as knee joint flexion, by harvesting body heat. This work offers a scalable and mechanically resilient platform for integrated thermoelectric energy harvesting, advancing the development of self-powered wearable electronics.