Session: 01-01: Liquid Metals

Paper Number: 111059

111059 - Printing Functional Elastomers for Stretchable Thermoelectric Devices 

Wearable thermoelectric (TE) devices have recently drawn attention since they can induce temperature change and harvest thermal energy from body heat. Unlike conventional TE modules that are rigid and brittle, flexible TE devices are commonly composed of rubbery elastomers with encapsulated semiconductor pellets. This device architecture provides conformal contact with complex surfaces and the flexible TE devices can be worn on the body. Recently, we have introduced multifunctional elastomer composites that enhance heat managements and deformability of such hybrid TE devices. Liquid metal droplets are dispersed in polydimethylsiloxane (PDMS) to produce liquid metal elastomer composites (LMEC). LMEC with microdroplets has a high thermal conductivity but it is an electrical insulator, so it functions as a thermal interface material in the device. On the other hand, hollow thermoplastic microspheres are embedded in PDMS to synthesize soft matter with low thermal conductivity which separates the top and bottom thermal interface layers and encapsulated the semiconductor pellets. The difference between the conductivity of the two composites facilitates a larger heat flux in TE pellets which improves the device performance. However, there are other factors that can influence the stretchability and thermoelectric energy conversion in these devices. In this presentation, we review the additive fabrication of TE devices with elastomer composites and bismuth telluride semiconductors. Liquid metal droplets and hollow microspheres are used to engineer the properties of each layer and formulate printable inks. Moreover, we demonstrate the significant role of device architecture in energy harvesting performance and durability of the printed thermoelectric devices under large deformations. After identifying the optimized device structure, several TE devices are fabricated and characterized at different temperature gradients. The results indicate that the new device architecture drastically increases the energy harvesting performance while reducing the device weight and material usage. This is achieved by simply manipulating the device structure and the design freedom offered by the 3D printing. Lastly, we demonstrate the potential applications of these thermoelectric generators. This novel design and the new insights from this research are applicable to other elastomeric TE devices while the functional elastomers can be utilized in various types of flexible electronics.

Presenting Author: Youngshang Han University of Washington

Presenting Author Biography: Youngshang Han is a Ph.D. student in iMatter lab at the University of Washington. He is under the supervision of Dr. Mohammad Malakooti working on soft matter engineering, stretchable electronics, and energy harvesting.