The triboelectric effect (also known as 'triboelectric charging') is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties.

Thus, it is not very predictable, and only broad generalizations can be made. Amber, for example, can acquire an electric charge by contact and separation (or friction) with a material like wool. This property, first recorded by Thales of Miletus, suggested the word "electricity", from the Greek word for amber, ēlektron. Other examples of materials that can acquire a significant charge when rubbed together include glass rubbed with silk, and hard rubber rubbed with fur.

• Allen, Ryne, C, Triboelectric Generation: Getting Charged [1][2]
• Besançon, Robert M. (1985). The Encyclopedia of Physics, Third Edition. Van Nostrand Reinhold Company. ISBN 0-442-25778-3.
• Harvard University Background of the Triboelectric Effect [3]

Patents

• U.S. patent 3,086,131 — Earle W. Ballentine — "Triboelectric Generator"
• U.S. patent 4,990,813 — Gabriel L. Paramo — "Rolling triboelectric generator"

General

• "Millennium Product — the Tribopen" Wolfson Electrostatics.
• "Charged Rod Demonstration" University of Minnesota, Crookston
• "Crackling Planets" NASA Science