Electrokinetic detection and separation of living algae in a microfluidic chip: implication for ship's ballast water analysis.

Detecting living algae from treated ship’s ballast water is an important task for port state control (PSC) under the requirement of the International Ballast Water Convention. In this paper, electrokinetic detection and separation of living algae from NaClO- and UV-treated ship’s ballast water in a microfluidic chip are presented. The electrokinetic movement of algae in a straight poly ethylene glycol (PEG)–modified PDMS microchannel filled with 10% PEG solution was measured by using an optical microscope. The experimental results show that the moving velocity of dead algae is lower by more than 80% in comparison with living algae. The decreased velocity is larger for larger dead algae and the velocity is decreased to zero for dead algae larger than 6 μm in diameter. A curve was obtained to evaluate the vitality of algae with similar moving velocity but different sizes. Electrokinetic separation of living algae from a mixture sample in a straight channel was also achieved. The method presented in this paper provides a moving velocity–based approach for quickly evaluating the living status of algae in treated ship’s ballast water.