Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150194

150194 - All-Printed Multi-Material Flexible Thermoelectric Devices 

Wearable Thermoelectric (TE) devices have multiple applications that can benefit humanity. Through the Peltier effect, TE wearable devices create a thermal gradient that can be used to regulate temperature at specific locations of the body. Conversely, they can turn body heat emissions directly into electricity to power other devices. Despite recent advances in creating TE devices for wearable applications, a viable materials and manufacturing approach remains a challenge, owing to tradeoffs between device flexibility and TE performance, the generally low performance inherent in TE materials, and the complexity of current fabrication approaches. This project aims to solve these challenges through an integrated approach combining new multi-scale composite TE material designs with multi-material Direct Ink Writing (DIW) 3D Printing. The efficiency of a TE device is directly dependent on the TE figure of merit and power factor of the materials used as legs. While inorganic materials possess the current highest figures of merit, organic TE materials have recently been the focus of studies due to their improved flexibility, lower costs, and processability. Moreover, doping of organic materials has been successful in producing flexible films with ultra-high Seebeck coefficients. Thus, a flexible, doped-conductive polymer composite is used as the base for the p-type TE material in the device. A systematic approach is taken to maximize the power factor of the material concerning dopant selection and concentration. Unlike past flexible TE organic materials, which are highly reliant on complex spin-casting manufacturing methods and managed in ultra-thin film geometries, our p-type composite will initially be manufactured as a printable ink, which will enable automated manufacturing via DIW multi-material printing. For the initial device, a Silver or Gallium-based ink replaces the n-type legs within the architecture and serves as the electrode throughout the device. To minimize losses, the electrode ink material design ensures a low or negative Seebeck Coefficient, while maintaining a high electrical conductivity. Lastly, an insulative and stretchable Polydimethylsiloxane (PDMS)-based composite, will serve as the packaging and separator ink throughout the device. The shear-yielding and viscoelastic properties of the three inks will be investigated through rheological characterization, to confirm compatibility with the DIW process. Although material design is imperative in creating an efficient TE device, improvement of power density through device architecture is an important tool to further enhance performance. Using a flat plate architecture for the initial device configuration, the optimization of the device can be done through a parametric programming approach, where the TE leg length and leg height can be easily varied to create new programmed printing paths. In contrast to conventional manufacturing methods for TE devices, where individual material properties are highly dependent on the manufacturing approach, DIW offers the capability for optimization of device performance and material performance to be carried out independently. Then, through automated multi-material DIW 3D printing, multiple programmed architectures can be printed sequentially and compared for power density and device efficiency. The material designs for the three inks, as well as the final devices, will be designed and tested for wearability through mechanical testing. 

Presenting Author: Nicole Bacca Boston University

Presenting Author Biography: I received my Bachelors degree in Mechanical Engineering at Florida International University in 2021. My research background has focused on developing new materials and testing methods for aerospace and biomedical applications. In my graduate studies, I have received the Clare Boothe Luce Fellowship as well as the National Science Foundation Graduate Research Fellowship to fund my current research focused on the 3D printing of stretchable electronics using additive manufacturing.

Authors:

Nicole Bacca Boston University
William Boley Boston University