CAREER: Interfacial Engineering and Additive Printing of Flexible Thermoelectric Materials

University Of Maryland Baltimore County, Baltimore MD

Investigators

Abstract

This Faculty Early Career Development (CAREER) grant supports research focused on the independent control of electrical and thermal properties of thermoelectric composite films through interfacial engineering using additive-printing methods. The research aims to enable flexible thermoelectric devices that can harvest low-grade waste heat and generate a voltage output that can be used to charge sensor capacitors and batteries. These self-sufficient power supplies can eliminate the need for periodically charging health-monitoring devices and enable the uninterrupted monitoring of health parameters. These power supplies can also accelerate the adoption of continuous monitoring sensors used in wearable devices, buildings, structures, and defense. Existing additive manufacturing methods used for fabricating flexible thermoelectric devices involve long duration and high temperature curing cycles making them energy intensive. The state-of-the-art composite thermoelectric films, building blocks of thermoelectric devices, suffer from low performance due to the presence of insulating binder, poor interfacial connection between active particles, and interdependence of electron and phonon-transport properties. The scientific understanding of decoupling electron- and phonon-transport properties by modifying composite micro and nanostructures and interfaces using low-energy-input processing methods is necessary for improved thermoelectric performance. The availability of high-efficiency thermoelectric devices impacts the national priority of Clean Energy. The integrated research, education, and outreach components include expanding the mechanical engineering curriculum by introducing a course on flexible electronics, creating a new program to offer paid research opportunities to a diverse group of students, and developing a thermoelectric-generator kit for K-12 students. This research aims to decouple electron- and phonon-transport properties in thermoelectric composite films using low-energy-input stencil additive-printing methods which involve (1) the tuning of the distribution of thermoelectric particle (micro and nano) sizes, (2) creation of nanoscale binder interfaces, and (3) modification of composite micro and nanostructures using moderate curing and uniaxial pressure. Tuning the distribution of particle sizes establishes tradeoffs between micron sized particles, which provide a large mean free path for charge carriers, and nanosized particles and defects, which facilitate phonon scattering. The study of the nanoscale binder interfaces examines the interplay between how the binder amount affects electrical connection among active particles, facilitates thermal resistance, and influences the mechanical properties such as flexibility, adhesion, and strength of the film. The tuning of external uniaxial pressure develops a fundamental understanding of how applied pressure initiates defects and impacts thermoelectric properties. The research also demonstrates a proof-of-concept scalable flexible-thermoelectric generator (TEG) device, using the additive-printing method and roll-to-roll processing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.