Researchers at City University of Hong Kong have developed an electrostatically charged face mask that can replenish its charge through the wearer’s breathing action. The electrostatic charge helps the mask to adsorb tiny particles, such as SARS-CoV-2 viruses. However, such masks typically lose their charge and ability to bind particles over time, particularly in humid environments such as right in front of the mouth. To address this, these researchers have created a mask with two triboelectric nylon fabric layers that replenish the charge as the layers move back and forth during breathing. The masks can provide protection against airborne viruses for much longer than conventional masks, enhancing the safety of healthcare staff and reducing waste.
The humble face mask has been a key component in our fight against COVID-19. For most of us, face masks were a mild inconvenience when we went to the store, mid-pandemic, in an effort to reduce viral transmission in the community. However, for healthcare staff caring for COVID-19 patients, effective masks are crucial for both personal and patient safety.
An effective mechanism that designers can deploy in face masks involves electrostatic adsorption, where an electrostatic charge helps tiny particles to stick within the masks, helping to complement the mechanical filtration that the masks provide. However, this electrostatic charge is depleted over time, particularly in humid conditions, which are difficult to avoid in something you breath through. This means that the masks may not be providing optimal protection for their entire duration of wear and also that masks must be exchanged frequently, creating waste.
This latest facemask technology maintains its protection against viral particles by generating electric charge from the movement of the breath. “Although many reports work on replenishing the charge for long-lasting electrostatic adsorption efficacy, an extra power source is generally needed, which is cumbersome and inconvenient,” said Yang Zhengbao, a researcher involved in the study. “We have developed an efficient, durable, low-cost air filter that can continuously replenish the electrostatic charge in a self-charging manner.”
The technology relies on triboelectric nylon fabric layers that can create an electric charge when moved. “As the middle layer moves forth and back between the lateral layers with breathing, a charge transfer occurs between PVDF and nylon due to their large difference in electron affinity, resulting in the PVDF layer being negatively charged and the nylon layers positively charged,” said Zhengbao. “This self-charging process enables the continuous replenishment of the electrostatic charges and prolonged electrostatic adsorption.”
Study in journal Nature Communications: Self-charging electrostatic face masks leveraging triboelectrification for prolonged air filtration