Electrostatic Spray Disinfection Using Nano-Engineered Solution on Frequently Touched Surfaces in Indoor and Outdoor Environments

Abstract

The COVID-19 pandemic has resulted in high demand for disinfection technologies. However, the corresponding spray technologies are still not completely optimized for disinfection purposes. There are important problems, like the irregular coverage and dripping of disinfectant solutions on hard and vertical surfaces. In this study, we highlight two major points. Firstly, we discuss the effectiveness of the electrostatic spray deposition (ESD) of nanoparticle-based disinfectant solutions for systematic and long-lasting disinfection. Secondly, we show that, based on the type of material of the substrate, the effectiveness of ESD varies. Accordingly, 12 frequently touched surface materials were sprayed using a range of electrostatic spray system parameters, including ion generator voltage, nozzle spray size and distance of spray. It was observed that for most cases, the surfaces become completely covered with the nanoparticles within 10 s. Acrylic, Teflon, PVC, and polypropylene surfaces show a distinct effect of ESD and non-ESD sprays. The nanoparticles form a uniform layer with better surface coverage in case of electrostatic deposition. Quantitative variations and correlations show that 1.5 feet of working distance, an 80 μm spray nozzle diameter and an ion generator voltage of 3-7 kV ensures a DEF (differential electric field) that corresponds to an optimized charge-to-mass ratio, ensuring efficient coverage of nanoparticles.

Keywords: COVID-19; disinfection; electrostatic spray deposition; fomites; nano-disinfectant; pathogens.

Figure A1

SEM image of stainless steel surface for non-ESD (left) and ESD (right) scaled to 1 mm.

Figure A2

SEM image of polyethylene surface for non-ESD (left) and ESD (right) scaled to 50 µm.

Figure A3

SEM image of Teflon surface for non-ESD (left) and ESD (right) scaled to 50 µm.

Figure A4

SEM image of PVC surface for non-ESD (left) and ESD (right) scaled to 50 µm.

Figure A5

SEM image of polypropylene surface for non-ESD (left) and ESD (right) scaled to 50 µm.

Figure A6

SEM image of wood surface for non-ESD (left) and ESD (right) scaled to 50 µm.

Figure A7

Wood: qualitative images of electrostatic deposition under various system parameters.

Figure A8

Wood: Quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A9

Aluminum: qualitative images of electrostatic deposition under various system parameters.

Figure A10

Aluminum: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A11

Copper: qualitative images of electrostatic deposition under various system parameters.

Figure A12

Copper: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A13

Cast iron: qualitative images of electrostatic deposition under various system parameters.

Figure A14

Cast iron: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A15

Stainless steel: qualitative images of electrostatic deposition at various system parameters.

Figure A16

Stainless steel: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A17

Polypropylene: qualitative images of electrostatic deposition under various system parameters.

Figure A18

Polypropylene: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A19

Polyethylene plastic: qualitative images of electrostatic deposition under various system parameters.

Figure A20

POLYETHYLENE PLASTIC: Quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A21

Teflon: qualitative images of electrostatic deposition under various system parameters.

Figure A22

Teflon: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A23

PVC: qualitative images of electrostatic deposition under various system parameters.

Figure A24

PVC: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A25

Rubber: qualitative images of electrostatic deposition under various system parameters.

Figure A26

Rubber: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A27

Aircraft sample-1: qualitative images of electrostatic deposition under various system parameters.

Figure A28

Aircraft sample-1: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure A29

Aircraft sample-2: qualitative images of electrostatic deposition under various system parameters.

Figure A30

Aircraft sample-2: quantitative representation of average differential electric field vs. working distance (feet), nozzle sprayer size ($\mathsf{\mu }$m), and charge voltage (kV).

Figure 1

Action of Nanoxen on pathogens (Taken from Nanoxen-Nano Coatings Technologies).

Figure 2

Electrostatic sprayer prototype.

Figure 3

Schematic of the experimental setup of the electrostatic spray deposition for varying system parameters.

Figure 4

Camera image of Teflon surface for non-ESD (left) and ESD (right).