Development of an Automated Electrostatic Sampler (AES) for Bioaerosol Detection

Abstract

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.

Primary biological aerosol particles in the atmosphere: a review

“…Each have their own advantages and disadvantages and these should be investigated thoroughly by the individual investigator. Electrostatic (Mainelis et al, 1999(Mainelis et al, , 2002Tan et al, 2011) and thermal precipitators (Kethley et al, 1952;Orr et al, 1956) have been developed in an attempt to collect viable aerosols with less damaging force. Recently, methods for online detection of biological aerosols have been developed using a variety of optical and additional techniques.…”

Aerosol sampling using an electrostatic precipitator integrated with a microfluidic interface

“…In comparison with results from Tan et al (2011), the relative collection efficiency of our ESP sampler was consistently ϒ relative = (1-n ESPoff / n ESPon ) ≈ 100%, without the large variations, ϒ relative = 70% -90%, seen from their sampler.…”

“…Similarly, Han & Mainelis [41] introduced an ESP sampler for bioaerosols, mainly targeting airborne pathogens and microorganisms, by collecting rolling water droplets off the collection electrode. Tan et al [42] proposed an airborne bacteria sampler using a semi-spherical electrostatic precipitator, and reported varying relative collection efficiencies, ϒ ESPon/ESPoff , from 50% to 100%, where the total capture was compared with that when no voltages were applied to the ESP electrodes. The collection was dependent on applied voltages, flow rates, particle sizes and geometrical design parameters.…”

Investigation of a New Electrostatic Sampler for Concentrating Biological and Non-Biological Aerosol Particles

“…However, interest in electrostatic methods is growing and studies recently showed that it is a suitable method to collect microorganisms (Table 1). Compared to collection by impaction methods, advantages of the electrostatic-sampling-based method are lower impaction stress (Mainelis et al 1999), lower pressure drop and lower power consumption (Tan et al 2011). Yao demonstrated that electrostatic sampling could achieve culturable bioaerosol concentration levels as much as nine times higher than the BioStage impactor (Yao and Mainelis 2006) and five to ten times higher airborne allergen and toxin concentration levels than the BioSampler (Yao et al 2009).…”