If an electrical load is then connected between the two surfaces, a small current will flow to equalize the charge potential. By continuously rubbing the surfaces together and then quickly separating them, the generator can provide a small alternating current. An external deformation is used to press the surfaces together and slide them to create the rubbing motion.
"For this to work, you have to use to two different kinds of materials to create the different electrodes," Wang explained. "If you rub together surfaces made from the same material, you don't get the charge differential."
The technique could also be used to create a very sensitive self-powered active pressure sensor for potential use with organic electronic or opto-electronic systems. The force from a feather or water droplet touching the surface of the triboelectric generator produces a small current that can be detected to indicate the contact. The sensors can detect pressure as low as about 13 millipascals.
Because the devices can be made approximately 75 percent transparent, they could potentially be used in touch screens to replace existing sensors. "Transparent generators can be fabricated on virtually any surface," said Wang. "This technique could be used to create very sensitive transparent sensors that would not require power from a device's battery."
While smooth surfaces rubbing together do generate charge, Wang and his research team have increased the current production by using micro-patterned surfaces. They studied three different types of surface patterning lines, cubes and pyramids and found that placing pyramid shapes on one of the rubbing surfaces generated the most electrical current: as much as 18 volts at about 0.13 microamps per square centimeter.
Wang said the patterning enhanced the generating capacity by boosting the amount of charge formed, im
|Contact: John Toon|
Georgia Institute of Technology Research News