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A numerical investigation of the mechanism by which viral particles suspended in physiologically relevant (i.e., high ionic strength) media can be electrokinetically sampled on a surface is presented. Specifically, sampling of virus from a droplet is taking place by means of a high frequency non-uniform electric field, generated by energized planar quadrupolar microelectrodes deposited on an oxidized silicon chip. The numerical simulations are based on experimental conditions applied in our previous work with vesicular stomatitis virus. A 3D computer model is used to yield the spatial profiles of electric field intensity, temperature, and fluid velocity inside the droplet, as well as the force balance on the virus. The results suggest that rapid virus sampling can be achieved by the synergistic action of dielectrophoresis and electrothermal fluid flow. Specifically, electrothermal fluid flow can be used to transport the virus from the bulk of a sample to the surface, where dielectrophoretic forces, which become significant only at very small length scales away from the surface, can cause its stable capture.

A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the “fingerprinting” capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres) captured by an AC electric field between planar microelectrodes is presented with a methodology for analyzing the resulting spectra by comparing relative peak intensities. The same principle is applied to dielectrophoretically captured M13 phage particles whose presence is indirectly confirmed with micro-Raman spectroscopy using NeutrAvidin-Cy3 as a labeling molecule. It is concluded that the combination of electrokinetically driven virus sampling and micro-Raman based signal transduction provides a promising approach for time-efficient and in situ detection of viruses.

In situ observations of submicron fluorescent tracers suspended in high ionic strength media sealed in a confined geometry are combined with 3-D simulations in order to provide a better understanding of the synergism between dielectrophoresis and electrothermal flows that cause rapid particle transport and trapping on the surface of planar quadrupolar microelectrodes. The influence of electrode design on the microfluidic patterns and observed particle collection is examined by employing two different types of microelectrodes in the experiments. The potential use of quadrupolar microelectrodes as means for achieving accelerated sampling and signal amplification in future surface based biosensor devices is illustrated with an experiment involving stable capture of antigen-coated polystyrene particles on the surface of an antibody-functionalized microelectrode array.Des observations in situ de traceurs fluorescents submicroniques en suspension dans des milieuxà force ioniqueélevée enfermés dans une configuration confinée sont combinéesà des simulations en 3-D dans le but de mieux comprendre la synergie entre lesécoulements de type diélectrophorèse etélectrothermique qui entraînent un transport rapide des particules et le piégeageà la surface des microélectrodes quadrupolaires planaires. On examine l'influence de la conception desélectrodes sur les schémas microfluidiques et la collecte des particules observées en employant deux types différents de microélectrodes dans les expériences. L'utilisation potentielle des microélectrodes quadrupolaires comme moyen de réaliser unéchantillonnage accéléré et l'amplification des signaux dans les biosenseurs futurs basés sur des surfaces, est illustréeà l'aide d'une expérience faisant appelà la saisie stable de particules de polystyrène enduites d'antigèneà la surface d'une rangée de microélectrodes fonctionnalisées par un anticorps.

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