Electroporation air disinfection system powered by TENGs

The modern world is very familiar with the impact of local epidemics and how these localized epidemics can turn into global pandemics. Several airborne pathogens can cause serious epidemics and threaten public health, including pathogens that can cause a person to develop pneumonia, asthma and the flu.

When a person is infected with a pathogen, that person can release micron-sized aerosols into the air containing dangerous bacteria and / or viruses. The release of pathogens is often unavoidable, as the release into the air is facilitated by common daily movements, such as breathing, coughing and sneezing. Small diameter aerosol parts, typically less than 1 micron, can travel for miles and therefore can pose a threat to many people, especially in indoor and confined spaces.

Let’s face it, pathogens are a part of everyday life and will continue to be so as long as humans are around. Microbial inactivation in the air is one of the most effective ways to prevent their transmission. However, commonly used High Efficiency Particulate Filters (HEPA) do not inactivate microbes.

HEPA filters are excellent for filtering out pathogens. However, if a pressure drop occurs in these filters, it will prevent the microbes from inactivating. Microbes that have not been inactivated cause a problem with filters that need to be replaced more regularly. Not only can the operator be exposed to pathogens, but pathogens can also be released into the air, thus negating the work already done by the filter. To counter this, scientists and engineers are looking to build air filtration systems that can inactivate microbes to prevent the spread of pathogens. A recently emerging development is an electroporation air disinfection system.

Electroporation is a physical process that relies on a strong electric field to damage the external structure of a pathogen, such as the membranes of bacteria or the capsids of viruses. These mechanisms have been carried out efficiently with inorganic nanowires stacked vertically on a flat electrode, generating very localized electric fields. This highly localized electric field can then be used to inactivate microbes. Disinfection by electroporation has already been confirmed for the disinfection of pathogens in water-based systems. However, until new research was published recently, there were no such developments for air disinfection systems due to the faster flow rates in challenging air ventilation systems.

There are many different nanogenerators that generate electrical energy from different energy sources. These devices are energy harvesting devices and are often used to power small components and devices that cannot be charged from the mains. Triboelectric nanogenerators, often called TENG, are among the most well-known nanogenerators. TENGs work by transforming the mechanical energy of their environment into electrical energy by harnessing kinetic energy through contact electrification and electrostatic charge induction mechanisms.

In contact electrification mechanisms, the materials used in TENGs become electrically charged due to frictional forces with an external stimulus. Second, the induction of electrostatic charges then distributes those charges through the material. TENGs are lightweight, inexpensive, self-powered devices that have a high voltage output. They have generated a lot of interest in air disinfection systems, and TENGs have also been used in water-based disinfection systems. Questions about air flow and whether TENGs were suitable for powering these disinfection systems led a research team to investigate recently.

Research teams from South Korea and China have built a self-powered air disinfection system that uses an electroporation mechanism to inactivate microbes in the air. The system is powered by vibration driven TENGs (V-TENGs). One of the challenges in introducing such methods of disinfection in air filtration systems has been the need for an external power supply. However, the researchers managed to overcome this thanks to TENGs, which convert mechanical vibrations in the air into electrical energy.

The mechanism of electroporation disinfection was made possible through the use of copper nanowires, the localized electric field damaging the external structures of pathogens, rendering them inactive. The electroporation disinfection mechanism assisted by the system design accelerated the loading and trapping of microbes.

Fig. 1: Operating principle of the resonance and vibration (RV) disinfection system for airborne microbes.

Thanks to its rational design, the air disinfection system promoted microbial transport and achieved more than 99.99% microbial inactivation in 0.025s. Microbial transport has been carried out at rapid, i.e. more difficult, airflows of 2 m / s and has consistently shown this performance in microbial disinfection. In addition, there were only minimal pressure drops. The system not only overcomes the speed limitations of other nanowire-assisted electroporation mechanisms, but it also shows that it is possible to use this type of disinfection method in commercial ventilation systems, which had been discussed. and questioned before.

As pathogens continue to cause epidemics around the world, there may be a need in the near future to move from a mechanism of disinfection by pure physical separation to one capable of separating pathogens and inactivating them, so that they no longer pose a risk. It remains to be seen whether these systems are commercially feasible compared to long-standing air filtration systems. Much will depend on whether the cost or necessity of destroying the pathogens is the determining factor for companies, institutions and governments that can use such filters in their ventilation systems.

Reference:

Kim SW. et al, Self-powered microbial disinfection induced by triboelectrification using a localized electric field enhanced by nanowires, Nature Communications, 12, (2021), 3693.