A novel concept for aerosol collection: dielectrophoretic actuation and trapping of aerosolised microspheres.

Transmission of pathogens through aerosols significantly impacts human and animal health and agricultural productivity, highlighting the importance of effective aerosol sampling methods. Electrostatic precipitation is highly regarded as a promising collection method. However, the technique generates ozone as a byproduct, potentially compromising the viability of collected bioaerosol samples [1]. Herein, dielectrophoresis was investigated as an alternative method for aerosol collection.

The dielectrophoretic collection of aerosolised 1 µm diameter fluorescent polystyrene latex (PSL) microspheres was explored in an 8 m3 aerosol chamber equipped with optical particle counters (OPCs, Alphasense) to monitor aerosol concentration. Indium tin oxide (ITO) coated glass slides were connected to four plates with different applied potentials: negative, positive, grounded and floating, at voltages between -10 kV to +10 kV. The collected particle count was normalised against the chamber concentration. The slides were imaged with an M7000 fluorescent microscope and then processed using Celeste 6 software. A simple collection device with a fan for directed airflow (Fig 1a) was built. The fan speed and positioning of the collection device were adjusted to gain insight into collection efficiency and optimisation.

Firstly, we found that dielectrophoretic collection was achieved and that positive and negative biases significantly outperformed grounded and floating plates in the PSL collection, with the positive bias showing a slight advantage (Fig 1b). A positive correlation was also observed between the applied voltage and PSL collection. Higher voltages create a stronger electric field, thus producing a greater dielectrophoretic force and increased particle collection. Moreover, the simple collection device achieved up to 15.7 % collection efficiency. Through the characterisation of the device, we determined that increasing the distance between the fan and collection slide, or reducing the fan speed, can increase the collection efficiency to 21.6 %.

Overall, these findings demonstrate the potential of dielectrophoresis as an alternative aerosol collection method. This approach may preserve the viability of bioaerosols more effectively than electrostatic collection, making it a promising alternative.

This work was supported by Research England-funded Biodetection Technologies Hub and the Engineering and Physical Sciences Research Council [grant number EP/X017591/1].

Reference: [1] Ouyang, H. et al. Control technologies to prevent aerosol-based disease transmission in animal agriculture production settings: a review of established and emerging approaches. Front Vet Sci 10, 1291312 (2023).