Development and Optimization of the Electrostatic Precipitator with Superhydrophobic Surface (EPSS) Mark II for Collection of Bioaerosols

Abstract

We recently developed an electrostatic collector for bioaerosols that electrostatically deposits biological particles onto a 3.2 mm electrode covered by a superhydrophobic substance. The deposited biological particles are removed and collected by rolling water droplets (20 or 40 microliter) which results in high concentration rates. The collector has been improved further by integrating it with an electrical charger. Here, we describe the development and optimization of the charger and collection chamber, while maximizing collection efficiency and minimizing particle loss. The resulting sampler is made of static dissipative material (e.g., Delrin), is shaped as a closed half cylinder, and is integrated with a charger. The sampler's round top section contains eight carbon fiber brushes (ion sources to charge particles), while its flat bottom section holds a rectangular collection electrode (254 £ 3.2 mm) made of pressed carbon fiber and coated with a superhydrophobic material.The optimized configuration of the EPSS Mark II had a collection efficiency of up to 84% when sampling airborne Escherichia coli at 10 L/min and for 10 min. The bacteria were accumulated in rolling water droplets as small as 20 microliters, and the sampler achieved sample concentration rates of up to 4.2 £ 10 5 /min. When the sampler was operated for a longer time period (60 min), its collection efficiency was 72%. The efficiency decrease was most likely due to a reduced particle removal from the electrode, but the difference was not statistically significant. Since the EPSS Mark II shows satisfactory collection efficiency and high sample concentration rate, it could serve as a basis for developing a field-deployable version of the sampler.

Design and Evaluation of the Field-Deployable Electrostatic Precipitator with Superhydrophobic Surface (FDEPSS) with High Concentration Rate

“…The field-deployable electrostatic precipitator with superhydrophobic surface (FDEPSS) was developed based on the EPSS Mark II (Han et al, 2015) so that it could be operated as a stand-alone device in the field. The device showed satisfactory collection efficiency when challenged with laboratory-generated bioaerosols.…”

“…In this sampler, airborne particles are electrostatically deposited onto a narrow electrode (2.1-3.2 mm in width) covered by a superhydrophobic substance and then removed and collected by rolling water droplets (5-60 µL) to achieve a high sample concentration rate (i.e., the ratio of particle concentration in the collection liquid versus the airborne particle concentration per time unit). The prototype EPSS has also been successfully tested with microscopy, ATP and qPCR sample analysis methods (Han et al, 2010(Han et al, , 2011(Han et al, , 2015. It also preserved integrity of the collected bacteria better than an impactor or an impinger (Zhen et al, 2013).…”

“…Since the carbon brushes are connected to high voltage and the collection electrode is grounded, this configuration creates an ion cloud which charges the incoming particles and then deposits them onto the collection electrode. The single-stage EPSS design requires only one single power supply for both charging and collection (Han et al, 2015), thus reducing the cost and complexity of its design and field deployment. The dual-sided collector is made of static dissipative material: homopolymer acetal (Delrin, Professional Plastics Inc., Fullerton, NY).…”

“…It also preserved integrity of the collected bacteria better than an impactor or an impinger (Zhen et al, 2013). The prototype EPSS model was further developed as a single-stage electrostatic collector with more effective materials for the sampler body and electrode, and optimized ionizer configuration (EPSS, Mark II) (Han et al, 2015). The EPSS Mark II is made of a static dissipative material (e.g., Delrin) and uses a collection electrode made of pressed carbon.…”

Molecular detection of airborne Coccidioides in Tucson, Arizona

“…Several other newer means of efficient collection include high-volume liquid impingers and electrostatic precipitation. 36,37 To date, successful atmospheric collection of Coccidioides by these methods has not been described in the scientific literature.…”