Reviewed by Lexie CornerSep 11 2024
According to a study published in Advanced Materials, University of Washington (UW) researchers have developed a flexible, durable electronic prototype that can harvest energy from body heat and convert it into electricity to power small devices like batteries, sensors, and LEDs.
The device is extremely durable; it continues to operate even after being punctured multiple times and stretched 2,000 times.
One common drawback of fitness trackers and other wearable devices is their reliance on batteries, which eventually lose power. This new technology raises the possibility that, in the future, wearable electronics could be powered by body heat.
I had this vision a long time ago. When you put this device on your skin, it uses your body heat to directly power an LED. As soon as you put the device on, the LED lights up. This was not possible before.
Mohammad Malakooti, Study Senior Author and Assistant Professor, Department of Mechanical Engineering, University of Washington
Traditionally, devices that convert heat into electricity have been stiff and brittle. However, the device that Malakooti and his colleagues have developed is highly flexible and soft, allowing it to conform to the curve of a human arm.
This device was created from scratch. The researchers began by simulating the optimal combination of materials and device structures and then fabricated nearly all components in the lab.
The device consists of three main layers. At the core are rigid thermoelectric semiconductors that convert heat into electricity. These semiconductors are encased in 3D-printed composites with low thermal conductivity, which enhances energy conversion efficiency while reducing the device’s weight. Printed liquid metal traces connect the semiconductors, providing stretchability, conductivity, and electrical self-healing.
To further improve heat conduction to the semiconductors while preserving flexibility, liquid metal droplets were embedded in the outer layers, as the metal remains liquid at room temperature. Malakooti's lab designed and developed everything except the semiconductors.
Beyond wearables, Malakooti envisions other potential applications for these devices, such as integrating them with electronics that generate heat.
Malakooti added, “You can imagine sticking these onto warm electronics and using that excess heat to power small sensors. This could be especially helpful in data centers, where servers and computing equipment consume substantial electricity and generate heat, requiring even more electricity to keep them cool. Our devices can capture that heat and repurpose it to power temperature and humidity sensors.”
Malakooti continued, “This approach is more sustainable because it creates a standalone system that monitors conditions while reducing overall energy consumption. Plus, there is no need to worry about maintenance, changing batteries, or adding new wiring.”
These devices also have the ability to function in reverse—by applying electricity, they can heat or cool surfaces, opening up new possibilities for applications.
“We are hoping someday to add this technology to virtual reality systems and other wearable accessories to create hot and cold sensations on the skin or enhance overall comfort. But we are not there yet. For now, we are starting with wearables that are efficient, durable and provide temperature feedback,” Malakooti stated.
Additional co-authors include Youngshang Han, a UW doctoral student in mechanical engineering, and Halil Tetik, a UW postdoctoral fellow in mechanical engineering who is now an assistant professor at Izmir Institute of Technology. Malakooti and Han are both members of the University of Washington's Institute for Nanoengineered Systems. The National Science Foundation, Meta, and The Boeing Company funded this research.
This stretchy, wearable device lights up an LED using only the warmth of your skin
Video Credit: University of Washington
Journal Reference:
Han, Y., et al. (2024) 3D Soft Architectures for Stretchable Thermoelectric Wearables with Electrical Self‐Healing and Damage Tolerance. Advanced Materials. doi.org/10.1002/adma.202407073.