The concept of powering watches with movement is nothing new. Automatic quartz watches combine rotating pendulums which actuate with the wearer's movement, spinning a small pinion at very high speed to charge a capacitor or battery. However, Samsung engineers are now looking at next-generation nanogenerators that would be capable of powering wearable electronics like smartwatches.
Triboelectric nanogenerators are small devices capable of converting movement into electricity. New research from the Samsung Advanced Institute of Technology (SAIT) in South Korea has demonstrated the ability to power or smart watch or a smartphone with the mechanical energy produced by typical body motions.
The research also characterised the effects associated with different forms of similar motions on the maximum producible energy they can produce in a triboelectric nanogenerator (TENG).
“We studied the possibility of charging commercialized portable and wearable devices by utilising the mechanical energy generated by human motion,” said Hyeon-Jin Shin, research master at SAIT.
“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.”
Shin and his team wanted to address the real-world feasibility of triboelectric nanogenerators in detail, and understand how they can 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 energy produced by the nanogenerators 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.
They found that even though vigorous typing was not yield enough enough energy to support an active tablet device, semi-passive activities could power smaller phones and smart watches by the power generated by the nanogenerators alone.
With close investigations of the mechanism that produces electricity in the device, they also discovered that the elasticity or impulse of the nanogenerator can also offer a boost to the amount of energy generated.
“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.
The characterisation of the energy that can be generated by a TENG is just the first step.
“The optimisation of output energy of a TENG in actual use remains a task for future work because a real system has many limitations such as impedance matching, frequency control, and the stability of the structure,” Shin said. “Nevertheless, the results of this study give insight into the design of a TENG to obtain a large amount of energy in a limited space.”