Tribocharging, the transfer of electrical charge between materials during contact, is one of the oldest topics of scientific inquiry, and is important in daily life, new technologies, and fundamental science. In thunderclouds, colliding ice crystals exchange charge so vigorously that they induce electrical breakdown in the air around them—a contributing factor to lightning. Triboelectric generators utilize the effect to convert mechanical contacts into electrical energy, and are being incorporated into wearable tech. Even the origin of the Earth may be connected with tribocharging, as attractions between protoplanetary dust may allow it to aggregate quickly enough before gas-induced drag causes it to spiral into its star.
Despite this universal relevance, we know remarkably little about how tribocharging occurs. The one area we do understand is charge exchange between metals, which is related to the work function and photoelectric effect. With insulators, however, even the most basic questions remain unanswered: What are the charge carriers (ions vs. electrons)? How are they bound to the surface? And what drives them from one surface to another?
The objective of this project is to determine the mechanism of tribocharging for insulators. To do this, we are building experiments that address different aspects of the phenomenon ranging from the scale of the everyday effect to the scale of the atoms/molecules that must be involved. Our work is based on testing the hypothesis that ions in adsorbed water contribute to the effect.
