Thin-film wearable thermoelectric generator produces electricity from body heat

Mar 18, 2026

A flat, flexible wearable thermoelectric generator converts body heat into electricity by redirecting thermal flow through a dual conductivity substrate.

(Nanowerk News) Researchers at Seoul National University have developed a flat, flexible wearable thermoelectric generator that converts body heat into electricity without requiring any bending or bulky structures. The team, led by Prof. Jeonghun Kwak of the Department of Electrical and Computer Engineering, engineered a substrate that redirects heat flow sideways rather than letting it escape vertically, enabling a usable temperature difference within a thin-film device worn on skin or clothing. The study was published in Science Advances (“All-solution-processed scalable and wearable organic thermoelectrics by structurally mimicking transverse thermoelectric effects”).

Key Findings

Thermoelectric generators convert temperature differences into electrical power and are considered promising for wearable electronics because they eliminate the need for batteries. Thin-film versions are lightweight and flexible enough to conform to skin or clothing, but their thinness creates a core problem. When a device sits flat against the body, heat passes straight through the film and dissipates into the surrounding air almost immediately, leaving no meaningful temperature gradient to drive electricity production. Earlier attempts to address this involved bending devices or building three-dimensional pillar-like architectures to create a longer heat path. These workarounds increased thickness and bulk, negating the very qualities that make thin-film devices attractive for wearable use. Instead of altering the geometry of the device, Kwak’s team changed the way heat moves through it. They created a substrate from stretchable silicone (PDMS) in which thermally conductive copper nanoparticles were selectively incorporated into specific regions. This produced a single substrate containing zones of high and low thermal conductivity side by side. Comparison between conventional TEG and pT-TEG. A conventional thin-film TEG placed on human skin (i.e., a planar heat source) cannot produce ∆T and ∆V in a longitudinal direction, whereas the pT-TEG with the dual-κ substrate can produce in-plane ∆T and ∆V by redirecting the heat flow. The figure also illustrates the annotations for the thermal conductivity and thickness of the substrate, as well as the temperature for each location. (Image: Reproduced from DOI:10.1126/sciadv.aea9094, CC BY) (click on image to enlarge) Prof. Jeonghun Kwak stated, “This study addresses the limitations of conventional thin wearable thermoelectric generators through a new structural approach that controls heat flow,” adding, “Its significance lies particularly in presenting a new thermoelectric platform capable of generating a temperature difference while maintaining a fully planar structure.” When thermoelectric semiconductor materials sit at the boundary between the high- and low-conductivity zones, heat from the skin no longer travels straight up and out. It flows laterally along the high-conductivity region instead. This redistribution creates relatively warm and cool areas on the substrate surface, establishing the temperature difference needed to generate electricity, all within a fully planar structure. The team named the device a “pseudo-transverse thermoelectric generator” because it structurally mimics the transverse thermoelectric effect, in which heat and electric current flow in perpendicular directions. The study is the first to show that thin-film devices can generate electricity by controlling heat flow direction at the substrate level rather than relying on device shape. Because the generator is fabricated through an ink-based printing process, it retains high flexibility and can be manufactured in various sizes and shapes. The modular design allows units to be combined and scaled up, similar to assembling building blocks. These characteristics make the technology suitable for applications in smart clothing, health monitoring sensors, and other wearable electronic devices. He further noted, “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.” Dr. Juhyung Park, co-first author, is currently a postdoctoral researcher at KU Leuven in Belgium, working on organic electronic devices. Dr. Sun Hong Kim, also a co-first author, joined the Department of Chemical Engineering at the University of Seoul in March 2025 and focuses on next-generation electronic systems based on soft electronic nanomaterials. The paper, titled “All-solution-processed scalable and wearable organic thermoelectrics by structurally mimicking transverse thermoelectric effects,” describes the full fabrication and characterization of the device. By managing thermal flow at the substrate level, the pseudo-transverse design removes the trade-off between device thinness and electricity generation that has constrained earlier wearable thermoelectric approaches. A flat, printable generator that harvests body heat without structural compromises could expand the practical scope of self-powered wearable sensors and electronics.