80-year-old static electricity mystery finally resolved
Seoul, South Korea: The two contacting/sliding materials were long believed to be evenly and diametrically charged. However, it was discovered that following CE, each of the split surfaces is carrying both (+) and (-) charges.
The inability to replicate the experiments, the innate inhomogeneities of the contacting materials, or the general "stochastic nature" of CE were all suggested as causes of the so-called charge mosaics.
For more than ten years, a research team at UNIST's Institute for Basic Science (IBS), under the direction of Professor Bartosz A. Grzybowski (Department of Chemistry), has looked for potential sources of charge mosaics. This study, which was published online and will appear in the October 2022 issue of Nature Physics, should assist in reducing the risk of electrostatic discharges.
"We demonstrated sub-micrometre-scale charge non-uniformity of unknown origin in our 2011 Science study [Science 333, 2011, 308-312]. At the time, our theory was that these (+/-) mosaics resulted from minute material patches moving between surfaces that were being separated. It gradually became unclear to us (and numerous other colleagues with whom we discussed this) how these microscopic patches can explain even millimetre-scale regions of opposite polarity coexisting on the same surface over the course of many years of work on the problem that this and related models were simply not holding up. However, neither the community nor we had a better explanation for why the (+/-) mosaics are observed over such a wide range of length scales "Professor Grzybowski explains.
"We demonstrated unidentified charge non-uniformity at sub-micrometre scales in our 2011 Science work [Science 333, 2011, 308-312]. Our theory at the time was that the transfer of minute patches of materials between the surfaces being separated was what caused these (+/-) mosaics. Over the course of several years of study into the issue, it gradually became apparent to us (and many other colleagues with whom we discussed) how these microscopic patches may account for even millimetre-scale regions of opposite polarity coexisting on the same surface. The (+/-) mosaics are observed over a wide range of length scales, but we and the community were at a loss for a better explanation "According to Professor Grzybowski.
The put-forward idea clarifies why charge mosaics were observed on a variety of materials, such as paper sheets, rubbing balloons, steel balls moving on Teflon surfaces, or polymers disengaged from the same or other polymers. It also suggests that the cracking sound you hear when you peel off a sticky tape is the result of plasma discharges that are pulling on the tape like a guitar string. The research team stated that the findings should aid in reducing electrostatic discharges that could be dangerous and advance our knowledge of the nature of contact electrification.
