UNIST Develops World's First Technology to Power Electronic Devices Using Only Body Heat

Solid-State Thermogalvanic Cell Generates AA Battery-Level Voltage with Body Heat
Paves the Way for Battery-Free Wearables and IoT Sensors
Developed by Professor Jang Sungyeon’s Team at UNIST and Published in Energy & Environmental Science

A technology capable of generating a voltage equivalent to an AA battery using only body heat has been developed.

This advancement is expected to accelerate the commercialization of wearable devices and Internet of Things (IoT) sensors that can operate without an external power source or charging.

On August 20, a team led by Professor Jang Sungyeon at UNIST announced that they have developed the world’s first n-type solid-state thermogalvanic cell with enough output to power actual electronic devices.

Research team, Professor Jang Sungyeon (left) and researcher Baek Jeongye (first author). Provided by UNIST

A thermogalvanic cell is a small generator that produces electricity using the temperature difference between human body heat and the surrounding air. However, since the temperature difference between body temperature (about 36°C) and air (20-25°C) is only a few degrees Celsius, it has been difficult to achieve enough output to power real electronic devices.

The solid-state cell developed by the research team can secure sufficient voltage and current, allowing it to generate output (voltage × current) capable of operating actual electronic devices. While solid-state cells are generally advantageous because they are not prone to leakage, they typically suffer from low current due to poor ion mobility within the solid electrolyte.

The research team designed the electrolyte to ensure efficient ion pathways. Additionally, thermal diffusion of ions led to further increases in voltage, thereby enhancing the overall output.

When 100 of these cells are connected in series, like Lego blocks, they can generate approximately 1.5V from body heat-equivalent to the voltage of a standard AA battery.

Furthermore, connecting 16 cells is sufficient to power devices such as LED lights, electronic watches, and temperature and humidity sensors. The Seebeck coefficient of a single cell is -40.05 mV/K, up to five times higher than conventional n-type cells. A higher Seebeck coefficient means a higher output voltage for the same temperature difference. The cells also demonstrated durability, maintaining consistent output even after 50 cycles of charging and discharging using body heat.

The developed solid-state cell is based on the conductive polymer ‘PEDOT:PSS’ and an Fe(ClO4)2/3 redox couple. The electrostatic bonding between the negatively charged sulfonate group (SO₃-) in the polymer chain and the cations (Fe²+/Fe³+) in the electrolyte enhances structural integrity, while the anions (ClO₄-) are able to move freely, creating efficient pathways.

Commercial electronic device operation using a module with developed thermogalvanic cells connected in series. Figure (a) Thermoelectric power (voltage) output of the module according to the temperature gradient. Figure (b) Temperature and humidity sensor operating for over 90 minutes. Figure (c) Operation of commercial electronic devices such as LED, temperature and humidity sensor, and electronic wristwatch.

Professor Jang Sungyeon stated, “This research marks a new milestone in the development of flexible thermoelectric conversion devices that utilize low-temperature waste heat,” adding, “It could serve as the foundation for self-powered systems supplying energy to wearable devices or autonomous IoT devices.”

The results of this research were published in the July 7 issue of Energy & Environmental Science, a journal of the Royal Society of Chemistry (RSC).

This research was supported by the National Research Foundation of Korea (NRF) under the Ministry of Science and ICT.

This content was produced with the assistance of AI translation services.