Researchers in South Korea have developed a way for body heat to power battery-free wearable gadgets and IoT sensors.

The research team from the Ulsan National Institute of Science & Technology (UNIST) has unveiled a technological advancement that allows body heat to generate electricity sufficient to power electronic devices. This paves the way for the commercialisation of battery-free wearables and IoT sensors that operate solely on heat generated by the human body.

Led by Sung-Yeon Jang from the School of Energy & Chemical Engineering at UNIST (www.unist.ac.kr), the research team announced they have developed the world’s first high-performance n-type solid-state thermogalvanic cell capable of powering actual electronic devices.

Thermogalvanic cells are compact generators that convert temperature differences – such as the human body temperature of about 36˚C versus surrounding air at 20 to 25˚C – into electrical energy. However, due to the minimal temperature gradient, previous systems struggled to produce enough power to operate real-world electronics.

The newly developed solid-state device overcomes this problem by delivering sufficient voltage and current to power practical devices. While solid-state designs typically offer advantages such as safety from leakage, ion mobility issues within the electrolyte have historically limited their current output. The research team engineered an electrolyte that facilitates efficient ion transport and, further, the thermally driven ion diffusion enhances overall output voltage.

By connecting 100 of these cells in series – similar to building with Lego blocks – approximately 1.5V can be generated from body heat, comparable with standard AA batteries. Connecting 16 such series-connected modules enables the activation of devices such as LED lights, electronic clocks and temperature or humidity sensors. Notably, the cell’s Seebeck coefficient (voltage change per temperature difference) is -40.05mV/K, representing up to a fivefold increase over conventional n-type cells. The device also demonstrated durability, maintaining consistent performance after 50 charge-discharge cycles.

“This research marks a new milestone in low-temperature waste heat energy harvesting and flexible energy conversion devices,” said Jang. “It has the potential to serve as a self-powered system for wearable electronics and autonomous IoT devices driven solely by body heat.”

This study (pubs.rsc.org/en/content/articlelanding/2025/ee/d5ee01216c) was published in the Energy & Environmental Science. The research was supported by the Ministry of Science & ICT (MSIT) and the National Research Foundation of Korea (NRF).