KERI's metamaterial, stretchable and efficient wearable thermoelectric energy harvester!

From National Research Council of Science & Technology 29/11/23

Stretchable/flexible thermoelectric generators using metamaterials. Credit: Korea Electrotechnology Research Institute(KERI)

A team of Dr. Hyekyoung Choi and Min Ju Yun from Korea Electrotechnology Research Institute (KERI) has developed advanced thermoelectric generator technology.

This technology uses ‘mechanical metamaterials’, which are artificially designed materials not found in nature.

Usually, materials shrink vertically when stretched horizontally, like a rubber ball flattening or a rubber band stretching. This is quantified by ‘Poisson’s ratio’.

Mechanical metamaterials, however, expand both horizontally and vertically when stretched horizontally, exhibiting a negative Poisson’s ratio.

KERI increased the stretchability of thermoelectric generators by 35% using a ‘gasket’ with a metastructure.

Design and fabrication of auxetic deformable gasket-based stretchable thermoelectric generators (TEGs): A) Schematic illustration showing partial air gaps in the TEG. Comparison between a typical rigid TEG, a flexible silicon-filled TEG and our deformable gasket-based TEG. B) Undeformed and deformed configurations of an auxetic structured deformable gasket having a negative Poisson’s ratio. C) Schematic illustration of the TEGs (left). Photograph of the fabricated TEG module with 8 pairs of thermoelectric legs attached to a hemisphere with a radius of curvature of 40 mm (right). Credit: Advanced Energy Materials

Thermoelectric generators convert temperature differences into electrical energy and are considered eco-friendly energy harvesters.

Until now, the rigidity of ceramic PCBs in thermoelectric generators limited their application on curved surfaces.

To improve flexibility, silicon and polymers were used, but their high thermal conductivity was problematic.

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For efficiency, it’s crucial for thermoelectric generators to maintain a large temperature gradient, which typical flexible materials hinder by causing heat loss.

Dr. Hyekyoung Choi’s team used a deformable gasket with a metastructure, enhancing the generator’s stability and flexibility.

This gasket, which stretches like human skin, has an internal air-gap that insulates and minimizes heat loss.

KERI’s thermoelectric generators are 35% more stretchable, with a power density more than 20 times higher than previous models.

Even when greatly expanded, these generators retain their electrical characteristics, marking a world-leading level of stretchability and efficiency.

The team ensured the generators maintain performance after over 10,000 repeated bends.

Dr. Hyekyoung Choi highlights the team’s expertise in thermoelectric materials, energy harvesting technology, and self-powered device stability.

This technology is expected to revolutionize IoT and AI-based wearable devices.

Existing wearables require separate power sources, but KERI’s technology enables electricity generation from body heat, potentially impacting next-generation medical fields.