Charged by water: open questions in liquid electrotribology

When a water drop slides on a hydrophobic surface, it can leave electric charge behind. Yet the nature of these charges and how they behave afterwards remain highly debated. In this talk, I will start by introducing liquid tribocharging, its state of the art, and a few recent results that raise questions. I will then present experiments by collaborators at ESPCI, in which surface potential mapping shows that charges initially confined to the drop’s path spread across the surface at an unexpectedly fast rate. Finally, I will show how molecular dynamics simulations help us better understand the state of these charges and what limits their motion on the solid. I will conclude with the open questions this raises and a possible route forward.