Triboelectric nanogenerators (TENGs) are capable of converting movement into electricity, but could it—even theoretically—pave the way for electronics that are powered solely by the wearer's body motion?

The answer is yes, according to a new research from Samsung Advanced Institute of Technology (SAIT) in South Korea.

The research, published in APL Materials, has demonstrated the ability of mechanical energy produced by typical body motions to power a watch or smartphone. It also characterises effects associated with different forms of similar motions on the maximum producible energy they can produce in a TENG.

"We studied the possibility of charging commercialised portable and wearable devices by utilising the mechanical energy generated by human motion," said Hyeon-Jin Shin, research master at SAIT and one of the authors of the study. "We confirmed that if the mechanical energy is entirely converted into electrical energy, the energy generated by the daily motion of an arm can sufficiently cover the energy consumption of a smart watch and even the stand-by energy consumption of a smart phone."

As interest in TENGs grows, particularly for wearable applications, Shin and collaborators wanted to address the real-world feasibility of the technology in detail and understand how to optimise the energy conversion.

"Over the past several years, many researchers have demonstrated a potential for energy harvesting using triboelectricity, and TENG's expectations as an energy source for wearable or portable devices have increased," Shin said. "It is important to confirm that the mechanical energy from human motion can cover the energy consumption of the devices to utilize a TENG for small devices."

The research team compared the achievable TENG energy produced in one minute by typical body movements, such as typing or arm swinging, to that consumed in the same time by a range of commercial electronics and wearables. Although even the most vigorous blogging would not yield enough energy to support an active tablet device, the theory showed the semi-passive activities could power smaller phones and smart watches by TENG power alone.

With close investigations of the mechanism that produces electricity in the device, they also discovered that its elasticity, not normally factored into calculating a TENG's maximum possible energy, can offer a boost to the value.

"To fully utilise the mechanical energy from human motion for the TENG, it is very important to increase the maximum possible energy of a TENG based on understanding the factors related to the motion in an aspect of the velocity (kinetic energy) and elasticity (impulse)," Shin said.