Determining electroosmotic velocity in a free liquid film

The flow field within a free liquid film under an applied external electric field was measured using confocal micro-PIV system. Free liquid films of thickness ∼ 200 μm were formed in a rectangular frame with electrodes in direct contact with the fluid and stabilised by cationic surfactant. The flow field induced by an external electric field of ∼1600 V/m was visualised using 2 μm tracer particles on several depth wise planes. The observed particle velocities were used to determine the fluid velocities within the film by accounting for the electrophoresis of the tracer particles.