Triboelectricity Effect

Triboelectric effect– the appearance of electric charges in a material due to friction (separation of materials after tight contact).

Even in antiquity, Thales rubbed an amber stick with a skein of wool and magnetized sawdust and shavings to the stick.

Soviet children rubbed an inflated balloon on their heads and then glued it to the ceiling. With the advent of office equipment, consumer electronics, packaging foam and beanbags (bean bags), seals have been used.

So what do we know at the moment about triboelectricity?

  • Tribology is a science, a branch of physics that deals with the study and description of the contact interaction of rigid deformable bodies during their relative displacement. The area of ​​tribological research is the processes of friction, wear and lubrication.
  • The triboelectric effect is highly unpredictable and only broad generalizations can be made.
  • A comprehensive theory of electrification has not yet been built, but many empirical patterns have been identified.
  • Cohen’s Rule : A material with a higher dielectric constant gets a positive charge. Cohen’s rule has been validated for over 400 substances.
  • The polarity and strength of the generated charges vary with materials, surface roughness, temperature, deformation, and other properties.
  • Triboelectric rows were experimentally found (for the first time by Johann Wilke in 1757): the substance located in the upper part of the row will be positively charged upon contact, and what is lower will be negatively charged.
  • There is also triboelectric ring : in a pair of silk-glass, glass is negatively charged, in a pair of glass-zinc, zinc is negatively charged, in a pair of zinc-silk, silk is negatively charged.
  • A person walking on carpet or taking off their nylon shirt or fidgeting in a car seat can create a potential difference of several thousand volts, which is enough to trigger a spark one millimeter or more long.
  • Electrostatic discharge may not occur in humid climates because surface condensation usually prevents triboelectric charging, and high humidity increases the electrical conductivity of the air.
  • In flight, the aircraft “rubs” against the air and accumulates a triboelectric charge.
  • NASA has a “triboelectrification rule” whereby they cancel a rocket launch if the launch vehicle is expected to pass through certain types of clouds.
  • Static discharge is especially hazardous in elevators due to the dust explosion hazard. The resulting spark is capable of igniting flammable vapors such as gasoline, ether vapors, and methane gas.
  • For bulk fuel supplies and aircraft refueling, a ground connection is made between the vehicle and the receiving tank before opening the tanks.
  • When refueling vehicles at a sales station, touching the metal of the vehicle before opening the gas tank or touching the injector can reduce the risk of static ignition of fuel vapors.
  • Some electronic devices, most notably CMOS integrated circuits and MOSFETs, can be accidentally damaged by high voltage static discharge. Such components are usually stored in conductive foam.
  • Grounding by touching a desktop or using a dedicated wrist strap or ankle strap is standard practice when working with unconnected ICs.

General model of an electron cloud and potential well proposed by Wang to explain triboelectrification and charge transfer and release between two materials, which may not have a well-defined energy band structure.

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