Enhanced bacterial accumulation on dielectrophoretic (DEP) structures via oscillatory flow induced by electrowetting-on-dielectric (EWOD)

Abstract

In this work, we propose one possibility to increase both the speed and the quantity of bacteria collected on a dielectrophoresis (DEP) structure for small sample volumes. To achieve this, an electrowetting-on-dielectric (EWOD) device was positioned opposite to the DEP structure. This setup allows oscillations of the droplet containing the bacteria, leading to a continuous flow within the droplet that brings new bacteria into the vicinity of the DEP electrodes, where the bacteria can be captured. Additionally, the EWOD electrodes can be employed to transport small liquid samples containing bacteria towards the DEP electrodes. To reduce the voltage required for the EWOD operation, a thin film of titanium dioxide was incorporated into the structure. The thickness of this layer, as well as the hydrophobic coating necessary for optimal EWOD performance, was optimized. Polymer microspheres were used for oscillation testing, and Escherichia coli (E. coli) served as the primary test organism. The behavior of these microparticles in a liquid environment was monitored microscopically.