The design (a) and schematic (b) of the mechanism of the device for capturing infectious droplets and aerosols without hindering communication. The negatively charged ions attach to the droplets and the electric field guides them to the collecting electrode. Credit: Assistant Professor Tetsuya Yamada
A novel device
developed by researchers from Tokyo Institute of Technology, Tokyo Medical and
Dental University, and Chiba University in a new study utilizes ions and an
electric field to effectively capture infectious droplets and aerosols, while
letting light and sound pass through to allow communication. The innovation is
significant in the wake of the COVID-19 pandemic, since it shows promise in
preventing airborne infection while facilitating communication.
Airborne infections, such as H1N1 influenza, SARS, and
COVID-19, are spread by aerosols and airborne droplets. While the
droplet/aerosol transmission can be prevented using acrylic partitions or, as
with the COVID-19 pandemic, by imposing lockdowns in severe cases, these
countermeasures can significantly impede communication. This, in turn, can lead
to unintended consequences.
For instance, lockdown measures during the COVID-19
pandemic led to severe economic losses as well as a rise in cases of mental
illness like depression and suicide around the world. Therefore, as we prepare
for a potential future pandemic, it is necessary to develop more sustainable
countermeasures that do not disrupt economic activities and daily face-to-face
interactions.
To this end, a research team including Kaito Kanda, a
graduate student at Tokyo Institute of Technology (Tokyo Tech) at the time of
research, Assistant Professor Tetsuya Yamada, from the Institute of Innovative
Research at Tokyo Tech, and Professor Takeo Fujiwara from Tokyo Medical and
Dental University (TMDU) and Chiba University researchers, has now developed a
device that successfully captures droplets and aerosols while allowing the
transmission of light and sound for effective communication.
A groundbreaking achievement in droplet
containment during Mr. Kanda's validation experiments with the prototype.
Credit: Kaito Kanda
Their work, which presents a novel solution for preventing the transmission
of airborne pathogens, including the coronavirus, was published in Scientific
Reports on 26 August 2023.
"While traditional partitions play a role in preventing airborne
infection, they have been known to obstruct smooth communication by affecting
the visibility of facial expressions and blocking voices. Recognizing these
issues after experiencing limitations in communicating with my grandfather in a
partitioned meeting area at a nursing home, we decided to tackle the challenge
of reconciling airborne infection prevention and communication," explains
Mr. Kanda.
Subsequently, during a symposium hosted by the Consortium for
Post COVID-19 Society in 2021, students and researchers from the union
of four universities in Tokyo, including Tokyo Medical and Dental University,
Tokyo University of Foreign Studies, Tokyo Institute of Technology, and
Hitotsubashi University, engaged in a group discussion concluded that
partitions should be further improved.
The students in the group had created a prototype for new partitions at
Tokyo Tech, and researchers from the TMDU, actively involved in COVID
treatment, conducted validation experiments in the clinic.
To enable unimpeded communication, a device must allow the transmission of
sound and light. At the same time, it must capture the sources of infection,
i.e., airborne droplets and aerosols. The researchers found a solution by
harnessing pre-existing ion and electric field-based aerosol
capture technologies utilized in air purifiers.
"As a verification step, we first captured incense smoke near an ion
and electric field generator. In regions where no ions or electric field were
present, the smoke rose naturally, while it was drawn downward in places where
the device was operational," adds Dr. Yamada.
It was also critical to ensure that the ions and electric field did not hinder
the transmission of sound and light. Notably, conventional six-mm-thick acrylic
panels used in partitions reflect light, limiting the perception of facial
expressions during conversation.
In contrast, ions and electric field demonstrated high light transmittance—equivalent
to that of air. Similarly, while acrylic panels interfered with sound, ions and
electric field allowed sound to pass through like air. These results showed
that ions and electric field enabled the transmission of light and sound while
capturing aerosols.
Encouraged by these results, the researchers created a device that
generates ions and an electric field. The ozone concentration generated in it
was below 0.001 ppm, and the electric field strength at a distance of 30 cm
from the device ranged from 10–45 kV, undetectable by humans.
By introducing aerosols simulating a light cough to the proposed device,
the team demonstrated that it could block 89% of the droplets at an opening
height of 16 cm. Finally, a prototype was installed in hospital rooms where
patients infected with COVID-19 had been admitted. "The device
successfully captured aerosols, including the coronavirus, reducing the viral
load in the room," says Prof. Fujiwara.
The present study demonstrates the effectiveness of the newly developed device in blocking out droplets and aerosols while allowing for communication.
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