Everyone has experienced this when taking off a sweater or walking on a carpet in plastic shoes. Friction generates static electricity, especially in dry winter weather, usually accompanied by sparks and small bumps. Already 2,600 years ago the Greek scientist Thales of Miletos had found that rubbing amber on stoles produced such effects – hence the term “Triboelectricity” from the Greek tryin what does “rub” mean and êelectron which means “amber”. “It is the oldest observed manifestation of electricityrecalls Philippe Molinié from the Laboratory of Electrical Engineering and Electronics in Paris. Although the phenomenon of triboelectricity is known and used today in various technologies such as photocopiers or laser printers, it is still poorly understood on a microscopic scale. However, researchers at Northwestern University near Chicago (USA) have just shed new light on its origin. In their opinion, imperceptible deformations would play an important role, which until then would be ignored.
Everyone has experienced this when taking off a sweater or walking on a carpet in plastic shoes. Friction generates static electricity, especially in dry winter weather, usually accompanied by sparks and small bumps. Already 2,600 years ago the Greek scientist Thales of Miletos had found that rubbing amber on stoles produced such effects – hence the term “Triboelectricity” from the Greek tryin what does “rub” mean and êelectron which means “amber”. “It is the oldest observed manifestation of electricityrecalls Philippe Molinié from the Laboratory of Electrical Engineering and Electronics in Paris. Although the phenomenon of triboelectricity is known and used today in various technologies such as photocopiers or laser printers, it is still poorly understood on a microscopic scale. However, researchers at Northwestern University near Chicago (USA) have just shed new light on its origin. In their opinion, imperceptible deformations would play an important role, which until then would be ignored.
Charge transfer between the two materials
“Electrification occurs when two materials that have touched are separated from each other”, specifies Philippe Molinié. This separation mostly results in charge transfer between the two materials, one becoming electrically “positive” and the other “negative”. Charges can be carried by electrons, ions, or even molecular aggregates, as various studies have shown. “But that’s more or less the end of the scientific consensus”says physicist Laurence Marks, who led this new work. “Various mechanisms appear to be involved in charge migration”continues Philippe Molinié: difference in structure and chemical composition, temperature increase at the contact points, quantum phenomena, etc.
Reliefs of a few billionths of a meter
Northwestern University researchers offer a new explanation. No surface is perfectly smooth, they point out first. They all have a kind of relief, with bumps and depressions of a few billionths of a meter. The fact that two materials are attached and rubbed thus compresses and relaxes these tiny protrusions. However, the gradual deformation of the material creates potential differences between the elevations and depressions that can reach several volts, the American physicists discovered. This is more than enough to cause charge separation. Emphasized in the special case of ceramics and polymers, this mechanism would play a role “significant and maybe even outstanding” the American researchers point this out in many other situations.