One in all the drawbacks of fitness trackers and other wearable devices is that their batteries eventually run out of juice. But what if in the longer term, wearable technology could use body heat to power itself?
UW researchers have developed a versatile, durable electronic prototype that may harvest energy from body heat and switch it into electricity that may be used to power small electronics, similar to batteries, sensors or LEDs. This device can also be resilient — it still functions even after being pierced several times after which stretched 2,000 times.
The team detailed these prototypes in a paper published Aug. 30 in Advanced Materials.
“I had this vision a protracted time ago,” said senior creator Mohammad Malakooti, UW assistant professor of mechanical engineering. “Whenever you put this device in your skin, it uses your body heat to directly power an LED. As soon as you place the device on, the LED lights up. This wasn’t possible before.”
Traditionally, devices that use heat to generate electricity are rigid and brittle, but Malakooti and team previously created one which is extremely flexible and soft in order that it could conform to the form of somebody’s arm.
This device was designed from scratch. The researchers began with simulations to find out one of the best combination of materials and device structures after which created just about all the components within the lab.
It has three important layers. At the middle are rigid thermoelectric semiconductors that do the work of converting heat to electricity. These semiconductors are surrounded by 3D-printed composites with low thermal conductivity, which boosts energy conversion and reduces the device’s weight. To offer stretchability, conductivity and electrical self-healing, the semiconductors are connected with printed liquid metal traces. Moreover, liquid metal droplets are embedded within the outer layers to enhance heat transfer to the semiconductors and maintain flexibility since the metal stays liquid at room temperature. Every part except the semiconductors was designed and developed in Malakooti’s lab.
Along with wearables, these devices could possibly be useful in other applications, Malakooti said. One idea involves using these devices with electronics that get hot.
“You possibly can imagine sticking these onto warm electronics and using that excess heat to power small sensors,” Malakooti said. “This could possibly be especially helpful in data centers, where servers and computing equipment devour substantial electricity and generate heat, requiring much more electricity to maintain them cool. Our devices can capture that heat and repurpose it to power temperature and humidity sensors. This approach is more sustainable since it creates a standalone system that monitors conditions while reducing overall energy consumption. Plus, there isn’t any must worry about maintenance, changing batteries or adding recent wiring.”
These devices also work in reverse, in that adding electricity allows them to heat or cool surfaces, which opens up one other avenue for applications.
“We’re hoping someday so as to add this technology to virtual reality systems and other wearable accessories to create cold and hot sensations on the skin or enhance overall comfort,” Malakooti said. “But we’re not there yet. For now, we’re starting with wearables which can be efficient, durable and supply temperature feedback.”
Additional co-authors are Youngshang Han, a UW doctoral student in mechanical engineering, and Halil Tetik, who accomplished this research as a UW postdoctoral scholar in mechanical engineering and is now an assistant professor at Izmir Institute of Technology. Malakooti and Han are each members of the UW Institute for Nano-Engineered Systems. This research was funded by the National Science Foundation, Meta and The Boeing Company.
