In high school physics classes, students are often taught that static electricity develops when electrons detach from the surface of one object and jump to another, causing a difference in charge. Since opposite charges attract, the two objects are drawn to one another (like your hair to a balloon). But new research published in the journal Science shows that static electricity is caused by more than just the exchange of individual electrons, and instead involves the transfer of bigger (yet still tiny) clumps of material.
Scientists conventionally believed that static electricity required friction between two different non-metals, which would tug at their electrons with different amounts of force. But last year, a group of researchers at Northwestern University found that two sheets of the same polymer, like Teflon, can generate static electricity, also called contact electrification (pdf).
After the discovery, some of the researchers, including chemist Bartosz Grzybowski, wanted to understand how it all worked. Grzybowski and his team created static electricity between several materials and then scanned the charged surfaces with a Kelvin probe force microscope. Rather than seeing the expected uniform distribution of charge, the researchers noticed that the surfaces were actually patchworks of positive and negative regions just tens of nanometers across. The positively and negatively charged pockets were nearly equal in total area, but that tiny difference was enough to generate an overall static charge.
Using a couple of spectroscopy techniques, the team sought to learn how the charged mosaics emerged. The tests showed that when the surfaces of the materials rubbed together, nano-sized pieces of charged material transferred from one surface to the other. "It's not the inherent properties of two polymers that matter," Grzybowski told ScienceNews. "It's because of the material transfer that you develop charge."
The mathematician Thales of Miletus is often credited as the discoverer of static electricity. Around 600 B.C., the story goes, Thales noticed that amber attracted feathers and other light objects after being rubbed with fur. He believed that the rubbing rendered the amber magnetic.
Peter Halliwell, a chemist with the University of Sydney, believes that the new understanding of static electricity will be important in the long run. "It will allow for more sophisticated applications," he told ABC.
Not so fastDaniel Lacks, a chemical engineer at Case Western Reserve University in Cleveland, agrees that material is being transferred during static electricity, but believes that the new research doesn't completely rule out the old explanation for the phenomena. "We don't know yet whether that's the thing that dominates the charging," he told ScienceNews. "It could work in combination with other things."
The researchers have yet to work out a complete picture of what happens during static electricity. In addition to material transfer, they suspect the phenomenon involves chemical reactions and the breaking and forming of chemical bonds on opposite surfaces.