The role of changing contact in sliding triboelectrification

Sliding contact usually seems to promote triboelectric charge transfer between solids, but the reasons for this are not always clear. Existing theories propose a number of explanations, including an increase in contact area due to interfacial deformation, frictional heating and direct material transfer. In the absence of these mechanisms, sliding may still promote charging by occasioning a changing contact pattern. This changing contact results in a greater cumulative surface area available for charging than static contact. A theoretical structure is introduced to characterize the effect of changing contact on perfectly insulating surfaces with instantaneous contact charging. This is extended to include non-instantaneous charging by means of a simple charging-time model