Quantifying dissolution and biodegradation of oil droplets in flows by microfluidics and digital holographic microscopic interferometry (DHMI)*

The degradation of crude oil droplets in aquatic ecosystems is crucial process, particularly following major oil spills. Despite extensive research, understanding the mechanisms of degradation such as dissolution and microbial consumption as well as their rates remains challenging due to methodological limitations and study inconsistencies. Our study introduces an advanced methodology using an ecology-on-a-chip (eChip) microfluidic platform combined with DHMI to precisely evaluate the oil droplet degradation. The eChip replicates real-word hydrodynamic conditions, while DHMI provides high-resolution measurements of 3D droplet volume changes over relevant time scales (>weeks) with high precision. Our technique enables real-time evaluation of volume changes at a temporal resolution of 4 frames per minute (fpm) and spatial resolution of 7.4nm. Arrays of immobilized oil droplets are printed onto a substrate and placed in the eChip, with volume quantified directly using DHMI. The results demonstrate the capability of providing detailed insights into oil droplet degradation processes in realistic hydrodynamic and microbial environments.