TECH
Wearable thermoelectric technology uses thin films to generate electricity from body heat
Seoul National University College of Engineering has announced that a research team led by Prof. Jeonghun Kwak of the Department of Electrical and Computer Engineering, with co-first authors Dr. Juhyung Park and Dr. Sun Hong Kim, has developed a flexible and thin "pseudo-transverse thermoelectric generator" capable of producing electricity from body heat. The research findings appear in Science Advances.
Thermoelectric generators, which convert temperature differences into electricity, are attracting attention as a next-generation energy technology for wearable electronics because they can supply power without batteries. In particular, thin-film thermoelectric generators are lightweight and flexible, allowing them to be comfortably attached to skin or clothing.
However, this thin structure also presents a limitation. Thermoelectric generators require a temperature difference between hot and cold sides to generate electricity. When such a device is attached flat to the skin, body heat passes directly through the thin film and dissipates into the surrounding air—similar to heat passing through a sheet of paper. As a result, little to no temperature difference is formed across the device, making electricity generation difficult.
Previous studies have attempted to address this problem by bending the device or constructing three-dimensional, pillar-like structures. However, these methods increase thickness and volume, undermining the advantages of thin, flexible film-based devices.
Redirecting heat with dual substrates...To address this challenge, Prof. Kwak's team proposed a new approach that fundamentally redirects the flow of heat. They successfully designed a "dual thermal conductivity substrate" by incorporating thermally conductive copper nanoparticles into only selected regions of a stretchable silicone (PDMS) substrate, creating areas with high and low thermal conductivity within a single substrate.
When thermoelectric semiconductors are placed at the boundary between these regions, heat from the skin does not escape vertically but instead flows laterally along the high-thermal-conductivivity region. As a result, relatively warm and cool areas form on the substrate surface, creating a temperature difference that enables electricity generation even in a thin-film structure.
Through this approach, the study is the first to demonstrate that electricity can be generated even in thin films by maintaining a temperature difference through a new substrate structure that redirects heat flow. The research team named this technology a "pseudo-transverse thermoelectric generator," as it structurally mimics the conventional transverse thermoelectric effect.
Wearable power for future devices...The developed wearable thermoelectric generator can convert body heat into electricity even in a completely flat configuration, without requiring bending or structural deformation. It is fabricated using an ink-based printing process, ensuring high flexibility. Additionally, the device offers scalability, allowing its size and shape to be freely designed and scaled up easily, similar to assembling modular blocks.
These features are expected to allow the pseudo-transverse wearable thermoelectric generator to be widely used as a self-powered energy technology for various devices, including smart clothing, health monitoring sensors, and wearable electronics.
Prof. Kwak stated, "This study addresses the limitations of conventional thin wearable thermoelectric generators through a new structural approach that controls heat flow. Its significance lies particularly in presenting a new thermoelectric platform capable of generating a temperature difference while maintaining a fully planar structure.
"This technology has strong potential to be used as a power source for a wide range of wearable sensors and electronic devices that can be attached to the skin or clothing."
Provided by Seoul National University
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