Entry by Kelly Miller
The triboelectric series is a list that ranks materials according to their tendency to gain or lose electrons. The process of electron transfer as a result of two objects coming into contact with one another and then separating is called triboelectric charging. During such an interaction one of the two objects will always gain electrons (becoming negatively charged) and the other object will lose electrons (becoming positively charged). The relative position of the two objects on the triboelectric series will define which object gains electrons and which object loses electrons.
In the triboelectric series depicted below, materials are ranked from high to low in terms of the tendency for the material to acquire a positive charge. If an object high up on this list (asbestos, for example) were rubbed with an object low down on the list (silicon rubber, for example), the asbestos would lose electrons to the silicon rubber. The asbestos would, in this case, become positively charged and the silicone rubber would become negatively charged. The further away two materials are from each other on the series, the greater the charge transferred. Materials next to each other on the series might not become charged at all when they are brought in contact with one another. Materials in the middle of the list (steel and wood, for example) are items that do not have a strong tendency to give up or accept electrons.
Image Reference:[ http://www.esdsystems.com/whitepapers/wp_tribocharging.html]
It is the work function of a material that determines its position in the series. Generally speaking, materials with higher work functions remove electrons from materials with lower work functions. The work function is the minimum energy that must be given to an electron to free it from the surface of a specific material and is a function of the material itself.
Keyword in references:
"Folding of Electrostatically Charged Beads-on-a-String: An Experimental Realization of a Theoretical Model", Reches, M., Snyder, P.W., and Whitesides, G.M., Proc. Natl. Acad. Sci. USA, 2009, 106, 17644-17649.