Vain materials detect new physics of static electricity

Rub a balloon in your hair and balloon usually collects a negative electric load while your hair goes positively. But a new study shows that the load an object collects may depend on its story. The number of times that one object had previously affected another determined whether the object was negatively or positively charged when touched again, researchers report on February 20 Nature.

Work can be a step towards understanding the effects behind the static electricity phenomenon, in which the electrical charge accumulates in the materials after they are rubbed or touched together. Although static electricity is a daily phenomenon, scientists still do not understand how the tariff transfer works. The phenomenon is important for everything, from lightning storms to pollination. But “we are simply absolutely oblivious, like mega-clueless, for what is actually happening,” says physicist Scott Waitukititis of the Institute of Science and Technology Austria, or Ista, in Klosterneuburg.

Scientists do not know what is being transferred from one material to another when they touch the objects. They can be electrons, atoms loaded with electricity called ions or small pieces of material. Even reproducibility is a war: the same experiment can give a different result on different days or in different laboratories. This has made it difficult to draw clear conclusions.

So Waitukititis and colleagues simplified things. They studied electrical load in experiments with a single material, a sharp polymer called polydimethylloxane, or pdms. They touched different squares of the material together, measuring the transfer load. (Squishness is useful to ensure that both objects make good contact with one another in experiments.)

At first, the samples seemed to exchange the load by chance. But finally, the researchers discovered a model. A sample that had been affected in other samples many times would load negatively when touched on a fresh one.

The researchers also found that the samples formed what is known as a tribellectric series. This is a ranking based on which material in a pair receives a negative load, and which a positive load, when affected. For example, a balloon usually goes negative when touching your hair. But a affected balloon in Teflon would usually get a positive load. A tribellectric series usually includes different types of materials, but different pieces of PDMS formed their series. Contact history mattered there, too. The triberbolectric series formed after the samples had many previous contacts.

The researchers examined in detail the PDMS samples to determine what was causing the effect. They found that the samples that were repeatedly affected were softer at very small scale at a distance of about 10 nanometra.

What it means for the mysteries of static electricity is not yet clear. But the result illuminates the source of some of the confusion. “It helps [us] Understand the previous irresponsibility, in what you have these materials that you think are the same, but there will be delicate differences in nanostructure, “says the chemical engineer Daniel lacks Case Western Reserve University in Cleveland.” the main. ”

The discovery was “a mix between accidental and clean stubbornness on my part,” says Juan Carlos Sobarzo, also Ista, who performed experiments. When the experiments did not work as expected, he tried them again, day by day, until they did. This made the researchers realize that repetition in itself was essential to get a tribellectric series, in what samples should have been affected many times. “If I hadn’t followed my gut, we could have lost the importance of contact history.”

Sobarzo, it seems only to have the right touch.