Electrostatic charge generation on material surfaces from the evaporation of liquids

Electrostatic charging is a ubiquitous but poorly understood phenomenon. One of the difficulties with studying electrostatics is separating the different types of charging (triboelectric, inductive, or gas phase ion adsorption). We constructed an experiment to test how liquid film evaporation affects the charge on an insulator surface. Our results showed that when a liquid evaporates in an electric field, it leaves a charge on the substrate surface. It was also determined that the magnitude and polarity of the charge depends on the local electrostatic potential of the substrate and sufficient charge buildup leads to a dielectric breakdown of air, a potential source of hazardous sparks. We reveal through careful experiments that the charge is transferred via induction from electrical ground through the liquid film and onto the substrate's surface. Ambient fields were shown to be able to cause this type of charging, suggesting that failing to account for this phenomenon may explain the lack of reproducibility in previous electrostatic charging studies.