Body heat-to-electricity converter device bears piercing, stretches 2,000 times

Fitness trackers and other wearable devices have become increasingly popular, but they often face a common challenge: battery life.

Researchers at the University of Washington have developed a wearable device that can harness body heat to generate its own power. The generated electricity could be used to power various small electronic devices, including batteries, sensors, or LEDs.

What’s more, this flexible and robust electrical prototype gadget remained functioning despite being punctured and stretched 2,000 times.

“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 wasn’t possible before,” said Mohammad Malakooti, senior author and UW assistant professor of mechanical engineering.

Consists of three layers

The majority of devices that use heat for electricity generation are described as “rigid and brittle.”

The one created by Malakooti and his team is highly flexible and soft. This makes it comfortable to wear and can even mold to the shape of an individual’s arm.

They began by doing extensive simulations to develop this device. This allowed them to figure out the optimal combination of materials and device design.

This flexible, durable device is made up of three main layers: rigid thermoelectric semiconductors at the center, 3D-printed composites around them, and then printed liquid metal traces connecting the semiconductors.

The thermoelectric semiconductors turn heat into electricity. The 3D-printed materials boost energy conversion while reducing weight.

Lastly, the liquid metal traces provide stretchability, conductivity, and electrical self-healing. Moreover, liquid metal enhances device performance by improving heat transfer to semiconductors, thereby improving energy conversion.

Malakooti’s laboratory designed and developed all components of the device, except for the semiconductors.

Dual purpose device

Apart from wearables , these devices could be valuable in other areas, such as using them with electronics that generate excess heat.

“You can imagine sticking these onto warm electronics and using that excess heat to power small sensors,” Malakooti said.

“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. This approach is more sustainable because it creates a standalone system that monitors conditions while reducing overall energy consumption. Plus, there’s no need to worry about maintenance, changing batteries or adding new wiring,” he explained.

Interestingly, these devices serve a dual purpose — apart from generating electricity, it can also heat or cool surfaces.

“We’re 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,” Malakooti said in the press release .

He highlighted that the future is promising, but for now, they are focussing on laying the groundwork with efficient and durable wearable technology.

The findings were published in the journal Advanced Materials.