Rubber ducks

Rubber ducks electrified with nanogenerators

Image credit: Dreamstime

South Korean researchers have demonstrated that nanogenerators can be used to power battery-free rubber ducks with mechanical vibrations.

The children of today grow up with digital devices from earliest infancy. According to the American Academy of Paediatrics, virtually every child has had contact with an electronic toy or mobile device by the age of four.

Keeping these devices running – many on which we depend – requires constant charging or changing of batteries. For many years, researchers have been investigating alternatives to batteries which generate electricity from sources of otherwise wasted energy. These have included nanogenerators, which draw electricity from the flow of blood through a person’s veins and arteries, or from the friction of rolling tyres.

The latter uses the triboelectric effect, a phenomenon in which charging occurs when two different materials are rubbed together. Static electricity being generated when a balloon is rubbed on hair is a familiar example of the triboelectric effect. Triboelectric nanogenerators (TENGs) – which are made by sandwiching electrodes between a film – gather this electrical charge, amplify it and convert it into a form that can be used to power a device.

Although TENGs are well understood, they have not been scaled up for commercial applications, largely due to the very low conversion efficiency and amount of energy storage currently possible.

In order to work around these issues, a team of researchers led by Sang-Jae Kim and based at Jeju National University, South Korea, specialised TENGs and inserted them into traditional toys to turn them into self-powered toys, including rubber ducks and clapping toys.

These specialised nanogenerators work by gathering energy from vibrations that occur when the toys are played with. Squeezing or shaking the toys causes the electrodes to be rapidly separated from and brought into contact with the film, generating a potential difference. These TENGs are capable of collecting enough energy from these vibrations to illuminate several LEDs attached to the toys.

According to the researchers, this TENG design could lead to the creation of more complex battery-free toys, as well as medical devices and other electronics.

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