Development of an automated electrostatic sampler (AES) for bioaerosol detection

In this study, an automated bioaerosol collection and output system was developed using a new electrostatic sampling method. The electrostatic sampler was designed using a half-ball shape steel electrode (radius is 45 mm) with three aerosol inlets (radius is 3.5 mm) on the top and a copper plate electrode (6 and 16 mm in diameter) suited inside a circular plastic support. Above the plate electrode, a plastic cylindrical reservoir (14 mm in diameter and 1 mm in height) was built with liquid inlet and outlet made of copper (2 mm in diameter). These outlets are connected to a peristaltic pump for liquid delivery. Next to the reservoir, there are two aerosol outlets (radius is 2.5 mm) connected to a vacuum pump. The physical collection efficiencies of the system were investigated when collecting indoor particles using an optical particle counter under different experimental conditions. The system was also tested when sampling indoor and outdoor bacterial aerosols. Experimental data showed that the system could collect 70%-90% of indoor particles of 0.3-2 μm at a low sampling flow rate of 1.2 L/min when a 20 kV voltage and a particle charger (1.5 V) were applied. Increasing sampling flow rate was observed to lead to the decrease of the collection efficiency. When a particle charger was applied, use of larger plate electrode (16 mm in diameter) was shown to significantly improve the collection efficiency close to two times than that of 6 mm. When operated for sampling environmental bacterial aerosols, the system obtained a similar magnitude of bacterial aerosol concentration levels compared to a mixed cellulose ester (MCE) filter. The integration of the automated electrostatic sampler (AES) sampler developed here with a biosensor device could offer a promising platform for the automated bioaerosol sensing.