Biofilm around a single rising oil droplet in natural seawater samples under various conditions using ecology-on-a-chip (eChip) microfluidics

Recent studies reveal that extracellular polymeric substance biofilm can form around rising oil droplets and increase drag as the droplet rises in the water column. However, the characteristics of the streamer formation in a variety of real-world conditions remain unknown. Here, we present eChip microfluidic platform, enabling detailed observation of marine ecology (i.e., microbe-oil interaction) around a rising oil droplet in natural seawater samples. In this experiment, a single oil droplet with different sizes is generated and pinned in the microfluidic channel employing layer-by-layer hydrophilic functionalization and flow-focusing technique, and fresh seawater samples obtained under different conditions (e.g., location, depth, tide condition, salinity, etc.) are flowed in the channel. The life span of streamer is extended from streamer formed using pure bacterial culture to natural seawater. A gallery of streamer is presented to demonstrate distinct morphology of streamers under different conditions. The findings allow us to assess the life span of streamers in real world and contribute to the understanding of rising oil droplet transport behavior in marine ecosystem.