Using cardboard, tape and a pencil to produce energy

A small device made from cardboard, Teflon tape and a pencil is claimed to generate enough energy to power several diodes.

A team from EPFL, along with researchers from the University of Tokyo, used these materials to make an 8 cm² device that can generate more than 3 V — the same voltage as two AA batteries.

The principle underlying this system is: static electricity. When two insulators like paper and Teflon come into contact, they gain or lose electrons. The system is made up of two small cards, where one side of each card is covered in pencil. The carbon serves as the electrode.

Teflon is then applied to the opposite side of one of the cards. When brought together, they make a sandwich: two layers of carbon on the outside, then two layers of paper, and one layer of Teflon in the middle. They are then taped together in such a way that the Teflon and the second layer of paper do not touch each other, giving the system a configuration that makes it electrically neutral. The two insulators (ie, Teflon and paper) come into contact when a finger is pressed on the system. This creates a charge differential: positive for the paper, negative for the Teflon. When the finger is released and the cards separate, the charge passes to the carbon layers, which act as electrodes. A capacitor placed on the circuit absorbs the weak current that is generated.

To boost the device’s output, Xiao-Sheng Zhang, a postdoc at EPFL’s Microsystems Laboratory and the University of Tokyo, used sandpaper. Pressing the sandpaper firmly against the cards gives them a rough surface. This increases the contact area, which in turn improves the system’s output six times. If a finger is pressed on the cards at a rate of 1.5 times per second, for a short period of time the capacitor will release the same amount of voltage as that supplied by two AA batteries. This is enough to power micro- or nanosensors that need only a little electricity to run.

TENG

Research on the use of static electricity to generate energy, dubbed ‘TENG’ (triboelectric nanogenerator), began in 2012.

“The one that we developed in the framework of this European project is the first one to use natural, everyday and environmentally friendly materials,” said Jürgen Brugger, a professor at the Microsystems Laboratory. They could have applications in the medical field, for example. This paper system could potentially remove the need for conventional batteries. Another advantage is that it does not generate waste, since it can be incinerated or left to decompose naturally.

The device was presented at the IEEE-MEMS conference, a global congress in the area of nano- and microsystems.