Spontaneous Mosaics of Charge Formed by Liquid Evaporation

Commonly used liquids have a powerful effect on producing electrostatic patterns in dielectric surfaces. During evaporation, charges are built‐up on dielectric surfaces that support liquids but with an important difference: negative charges appear where the liquid evaporates while positive ones are formed within the residual liquid. After complete evaporation, the result is a mosaic of stable and fixed surface charges resulting in electrostatic potential gradients as large as 20 kV m−1, but charge partitioning can be suppressed with common surfactants. The results can be understood considering the Maxwell–Wagner effect where charge accumulation takes place during current flowing across the interface. All these findings help to explain the hitherto challenging problem of static electricity and the appearance of the ubiquitous electrostatic patterns in dielectrics, what it must be helpful for the controlling of electrostatic charges in industry or in common laboratory activities. Unprecedent results show that during the evaporation of common liquids, large positive and negative charge domains are naturally formed at the interface as the result of charge partition during phase transition. Charges are accumulated within the bulk liquid while negative charges are built‐up at the liquid–solid–air interface, resulting in a multipolar electret that can be understood considering the Maxwell–Wagner effect.