Measurements of airborne viruses via sampling have been critical issues. Most electrostatic samplers have been assessed for bacterial aerosols or micrometer-sized viral particles; however, sampling of submicrometer-sized airborne viruses is necessary, especially because of the high probability of their staying airborne and their deposition in the lower respiratory tract. Here, we present a novel personal electrostatic particle concentrator (EPC) for gentle sampling of submicrometer airborne virus particles. Owing to the enhanced electric field designed in this EPC, the collection efficiencies reached values as high as 99.3-99.8% for 0.05-2 μm diameter polystyrene particles at a flow rate of 1.2 L/min. Submicrometer-sized MS2 and T3 virus particles were also collected in the EPC, and the concentrations relative to their respective initial suspensions were more than 10 times higher than those in the SKC BioSampler. Moreover, the recovery rate of T3 was 982 times higher in the EPC (-2 kV) than in the BioSampler at 12.5 L/min because of the gentle sampling of the EPC. Gentle sampling is desirable because many bioaerosols suffer from significant viability losses during sampling. The influence of ozone generated, applied electrostatic field, and the flow rate on the viability of the viruses will also be discussed.

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Dielectrophoresis (DEP) is usually effective close to the electrode surface. Several techniques have been developed to overcome its drawbacks and to enhance dielectrophoretic particle capture. Here we present a simple technique of superimposing alternating current DEP (high-frequency signals) and electroosmosis (EO; low-frequency signals) between two coplanar electrodes (gap: 25 μm) using a lab-made voltage adder for rapid and selective concentration of bacteria, viruses, and proteins, where we controlled the voltages and frequencies of DEP and EO separately. This signal superimposition technique enhanced bacterial capture (Escherichia coli K-12 against 1-μm-diameter polystyrene beads) more selectively (>99%) and rapidly (~30 s) at lower DEP (5 Vpp) and EO (1.2 Vpp) potentials than those used in the conventional DEP capture studies. Nanometer-sized MS2 viruses and troponin I antibody proteins were also concentrated using the superimposed signals, and significantly more MS2 and cTnI-Ab were captured using the superimposed signals than the DEP (10 Vpp) or EO (2 Vpp) signals alone (p < 0.035) between the two coplanar electrodes and at a short exposure time (1 min). This technique has several advantages, such as simplicity and low cost of electrode fabrication, rapid and large collection without electrolysis.

Novel method for generating planar electrode patterns with enhanced dielectrophoretic bacterial capture.