A team of scientists, led by Ya Yang at the Beijing Institute of Nanoenergy and Nanosystems in China, developed a hybrid nanogenerator technology, which can harvest the energy of wrist movement to power electronic devices. The technology combines electromagnetic and tirboelectric energy conversion mechanisms, which greatly boosts the efficiency. To demonstrate how the new system performs, the scientists placed it in an electronic watch.
The nanogenerator is essentially a small box, with metal coils on the sides and a magnetic ball inside. It has a strap, made of nylon and a polymer composite, attached to the box and two electrodes. As the wearer creates a motion, the magnetic ball hits the coils, and thanks to the electromagnetic effect, the mechanical energy of the ball turns into electricity. As the ball moves, it also puts pressure on the watch strap, which causes the nylon and the polymer to come into contact. This triggers the triboelectric effect, which stimulates the movement of electrons between the electrodes.
In the study published in the recent issue of ACS Nano, the researchers explain that different movements of the wrist can affect the amount of energy that is generated. Apparently, by twisting the wrist for 40 seconds, the nanogenerator can produce the incredible 12mA, which is sufficient to power the watch for 7.5 minutes. To test how far they can go, the scientists attached a Li-ion battery and established that 3.6 hours of twisting wrist movement a day, should be enough to power the watch without interruption.
The only challenge in front of the guys now is to bring down the size of the device, so that it can be made suitable to carry around comfortably (as now it is quite bulky). However, the team believes that their hybrid nanogenerator can power numerous other electronic devices, such as pedometers. They are convinced that they can improve the technology to the extent to which wearable electronic devices will never need an external battery source. Instead, the energy generated by the human body will finally be fully utilized.
Image (c) ACS