Hydrodynamics of a rising oil droplet with drag-increasing streamer from natural seawater samples using ecology-on-a-chip (eChip) microfluidics

Understanding the transport behavior of rising oil droplets is essential for predicting their fate in marine environments, particularly in the context of large-scale spills such as the Deepwater Horizon. In this study, a microfluidic platform is used to generate a single micro-oil droplet within a microchannel filled with natural seawater, where a controlled flow is applied to replicate transport conditions. Under these conditions, filamentous bacterial aggregates known as extracellular polymeric substance (EPS) streamers formed and attached to the oil droplet. Micro-particle image velocimetry (μPIV) is conducted at multiple stages of streamer growth, from early development to full maturation, to capture the velocity field around both the droplet and the streamer. Control volume analysis is applied to quantify the instantaneous drag imposed by the streamers. These measurements allowed for the assessment of how EPS streamer formation affects hydrodynamic drag around a rising oil droplet. The findings contribute to a better understanding of biologically mediated processes influencing the transport and fate of oil droplets in marine ecosystems.