Contact electrification (CE) was mankind’s earliest and only source of electricity until about the 18th century, but its true nature remains a mystery. Today, laser printers, LCD manufacturing processes, electrostatic painting, plastic separation for recycling, etc. as a critical component of such technologies as well as a major industrial hazard (damage to electronic systems, explosions in coal mines, fires). in chemical plants) due to electrostatic discharges (ESD) accompanying CE. A study published in 2008 nature found that the ESDs of a simple adhesive tape in a vacuum were so strong that they produced enough X-rays to take an X-ray of a finger.
For a long time, it was believed that the two contact/slide materials were loaded in opposite and uniform directions. However, after CE, each of the separated surfaces was found to carry both (+) and (-) charges. The occurrence of charged mosaics has been attributed to the nonreproducibility of the experiment, the inherent inhomogeneity of the materials in contact, or the general “stochastic nature” of CE.
A research group led by Prof. Bartosz A. Grzybowski (Department of Chemistry) from the Center for Soft and Living Matter at the Institute of Basic Sciences (IBS) Ulsan National Institute of Science and Technology (UNIST) has investigated the possible sources of mosaic cargo for more than a decade. The research is expected to help control potentially harmful electrostatic discharges and was recently published in a journal
In the paper published recently in Nature Physics, the group of Professor Grzybowski shows that charge mosaics are a direct consequence of ESD. The experiments demonstrate that between delaminating materials the sequences of “sparks” are created and they are responsible for forming the (+/-) charge distributions that are symmetrical on both materials.
“You might think that a discharge can only bring charges to zero, but it actually can locally invert them. It is connected with the fact that it is much easier to ignite the ‘spark’ than to extinguish it,” says Dr. Yaroslav Sobolev, the lead author of the paper. “Even when the charges are reduced to zero, the spark keeps going powered by the field of adjacent regions untouched by this spark.”
The proposed theory explains why charge mosaics were seen on many different materials, including sheets of paper, rubbing balloons, steel balls rolling on Teflon surfaces, or polymers detached from the same or other polymers. It also hints at the origin of the crackling noise when you peel off a sticky tape – it might be a manifestation of the plasma discharges plucking the tape like a guitar string. Presented research should help control the potentially harmful electrostatic discharges and bring us closer to a true understanding of the nature of contact electrification, noted the research team.
References: “Charge mosaics on contact-electrified dielectrics result from polarity-inverting discharges” by Yaroslav I. Sobolev, Witold Adamkiewicz, Marta Siek and Bartosz A. Grzybowski, 8 September 2022, Nature Physics.
“Correlation between nanosecond X-ray flashes and stick-slip friction in peeling tape” by Carlos G. Camara, Juan V. Escobar, Jonathan R. Hird and Seth J. Putterman, 23 October 2008, Nature.
“The mosaic of surface charge in contact electrification” by H. T. Baytekin, A. Z. Patashinski, M. Branicki, B. Baytekin, S. Soh and B. A. Grzybowski, 23 June 2011, Science.
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