Collection and concentration of bacterial and viral aerosols by electrostatic precipitation (ESP) and electrowetting-on-dielectric (EWOD)

Near real-time detection and identification of potentially hazardous bioaerosols is essential for informing timely response and exposure assessment strategies. Personal aerosol samplers are commonly used for individual exposure assessment. An integrated system that combines sample collection, processing, and concentration could improve downstream analytical performance while reducing user burden.

In this study, a prototype bioaerosol collection and concentrating system combining electrostatic precipitation (ESP) and electrowetting-on-dielectric (EWOD) technologies was evaluated and compared with two commonly used personal bioaerosol samplers: the SKC BioSampler® and 37 mm filter cassettes hosting 0.8 µm polycarbonate filters. Laboratory experiments were conducted in a controlled aerosol chamber using multiple bacterial and viral aerosol surrogates: Bacillus atrophaeus spores, Pantoea agglomerans, Escherichia coli, MS2, and Phi6. Sampler performance was assessed by comparing relative recovery per liter of air sampled and raw sample concentrations using culture-based methods, quantitative polymerase chain reaction (qPCR), and endotoxin assays. Microbial viability following collection was also evaluated using culture analysis.

The ESP-EWOD prototype demonstrated efficient aerosol collection followed by automated elution into a microdroplet size elution volume, producing substantially higher raw sample concentration for qPCR and endotoxin analysis compared with the conventional samplers. However, the ESP-EWOD relative recovery per liter of air sampled was lower than that achieved by the SKC BioSampler® and filter cassettes, and ESP collection did not preserve viability of Gram-negative vegetative bacteria.

These results highlight trade-offs between collection efficiency and post-collection sample processing and concentration. Despite reduced relative recovery, the compact design and ability to deliver small volume, highly concentrated liquid samples with automated methods demonstrate the potential of the ESP-EWOD system for applications requiring portable bioaerosol sampling and integration with rapid analysis platforms.