Where precisely does the fluid in a jet drop come from?

The rupture of small bubbles at an air-liquid interface can aerosolize droplets containing particulates from the liquid. If microscopic particles, such as bacteria and viruses, are scavenged by the rising bubble, they can be concentrated into the top jet drop. Although the bursting process is typically an inertio-capillary phenomenon, viscous stresses influence the dynamics within the jet, along with the size of the top jet drop. However, how viscosity affects the origin of the fluid that ultimately resides in the top jet drop, is still unclear. Here we use numerical simulations and Lagrangian particle tracking to identify which parcels of liquid around the bubble ultimately end up in the top jet drop. We find that the liquid that forms the top jet drop is not evenly distributed around the bubble, and that viscous stresses influence these distributions. Because these distributions can affect the pathogen loading in jet drops, we anticipate our results to be relevant to the transport of disease causing viruses and bacteria from contaminated fluids.