S. Simon, M. Weber
Keywords: dielectrophoresis, microfluidic, detector, sensor, filter, water, diagnostic
Summary:Fluid-Screen, Inc. presents a bacterial concentration and filtration method based on dielectrophoresis (DEP). DEP has been known to induce particle motion since the 1960’s. However, yields and reproducibility have consistently been low in practice, reducing the potential of DEP for practical applications. Here we present a novel electrode design to induce high electric field gradients. This design allows rapid and efficient capture of diverse bacteria from aqueous solutions of varied conductivity. By using the novel spiral electrode design and tuning the electric field to species-specific frequencies, we show capture of over 99% of bacteria within seconds of gradient application. Our method of DEP induces responses in both the representative Gram-negative Escherichia coli and Gram-positive Enterococcus faecalis bacteria. Equilibrium repositioning of suspended bacteria can be seen within miliseconds for low-conductivity medium and within seconds for higher conductivity solutions such as environmental river water samples. Fluid-Screen capitalizes on the improved dielectrophoretic filter design as a module to directly detect bacteria from water samples for applications as diverse as environmental regulatory reporting and point-of-care medical diagnostics for acute infectious agents. Furthermore, DEP can be used to either attract or repel bacteria from the electrode based on the particles’ Clausius-Mossotti factor at different applied frequencies, allowing controlled capture and release of bacteria. By pre-filtering samples with DEP, we allow for concentration of low-level bacteria in aqueous samples for transport into any number of bacterial detection or identification apparatuses without time-consuming culture-based amplification methods. Finally, because DEP applies to all particles, the feature design can be optimized to manipulate other contaminants for universal medical diagnostics.