The earliest spark of electricity known to man was from contact electrification (CE)— when nearby surfaces become electrically charged.
Even today, it forms an important part of the technologies that operate laser printers, produce LCDs, and separate plastics for recycling. CE can also cause industrial hazards such as damage to electronic systems, explosions in coal mines or fires in chemical plants due to electrostatic discharge (ESD) which is accompanied by CE.
Previously, it was assumed that two materials in contact with each other or sliding against each other produce charges that are opposite and uniform.
