Researchers have created a prototype of an electronic device that is not only flexible and durable but also capable of converting body heat into electricity. This innovative device can power small electronics, including batteries, sensors, and LEDs. Remarkably, it maintains functionality even after being punctured multiple times and stretched 2,000 times.
A common issue with fitness trackers and other wearable gadgets is their batteries eventually depleting. Imagine if, in the near future, these wearable technologies could generate their own power using body heat!
Researchers from the University of Washington (UW) have designed a flexible and tough electronic prototype that captures energy from body heat to produce electricity for small devices like batteries, sensors, or LEDs. Importantly, this prototype remains operational after being pierced numerous times and stretched up to 2,000 times.
The research team shared their findings in a paper published on August 30 in Advanced Materials.
“I envisioned this concept long ago,” said senior author Mohammad Malakooti, an assistant professor of mechanical engineering at UW. “Once you apply this device to your skin, it harnesses your body heat to directly power an LED. The moment it is on, the LED lights up. This capability wasn’t feasible before.”
Typically, devices that convert heat to electricity are rigid and fragile; however, Malakooti and his team previously developed a variant that is highly flexible and soft, allowing it to conform to the contours of a person’s arm.
This device was crafted from the ground up. The researchers began by using simulations to identify the optimal materials and structure combinations, and then they created almost all of its components in their lab.
The prototype consists of three primary layers. The core features rigid thermoelectric semiconductors that perform the heat-to-electricity conversion. These semiconductors are surrounded by 3D-printed composites that have low thermal conductivity, which boosts energy transformation while reducing the weight of the device. To enhance stretchability, conductivity, and self-repairing capabilities, the semiconductors are linked by printed liquid metal traces. Additionally, liquid metal droplets are incorporated into the outer layers to aid in heat transfer towards the semiconductors and to keep the device flexible since the metal remains in liquid form at room temperature. Everything, apart from the semiconductors, was designed and created within Malakooti’s lab.
According to Malakooti, these devices could be valuable in various applications beyond wearables. For instance, they could be used with electronics that generate heat.
“You could attach these devices to warm electronics to utilize the excess heat for powering small sensors,” Malakooti explained. “This could be particularly beneficial in data centers, where servers use significant electricity and produce heat, which in turn needs even more energy for cooling. Our devices can capture that heat and convert it into power for temperature and humidity sensors, creating a more sustainable system that monitors conditions while lowering overall energy consumption. Moreover, there’s no need for maintenance, battery changes, or additional wiring.”
Interestingly, these devices can also function in reverse—they can heat or cool surfaces when electricity is added, leading to further potential use cases.
“One day, we hope to integrate this technology into virtual reality systems and other wearable accessories to produce temperature sensations on the skin or improve user comfort,” Malakooti expressed. “However, we are not quite there yet. For now, we are focusing on making wearables that are efficient, resilient, and capable of providing temperature feedback.”
Youngshang Han, a doctoral student in mechanical engineering at UW, and Halil Tetik, who conducted this research as a postdoctoral scholar at UW and now serves as an assistant professor at the Izmir Institute of Technology, are additional co-authors. Both Malakooti and Han are affiliated with the UW Institute for Nano-Engineered Systems. This research received funding from the National Science Foundation, Meta, and The Boeing Company.
