Clip-on Wearable Covid Sensor
A wearable, clip-on covid detector has been unveiled by researchers in the US...
The Fresh Air Clip, developed by a team at Yale, is an air sampler that can be clips onto your shirt collar. The small, lightweight, and mostly reusable device doesn’t need to be powered, so is much more suitable for portable applications. It can even detect exposures below the threshold dose needed for infection.
Developer Krystal Pollitt explains why this device is exciting, not only for tracking personal exposure, but also for identifying covid hot spots such as classrooms or restaurants. “We're not waiting to see if someone is infected and having them take a nasal swab, but [instead we monitor] the potential exposure of any number of people within that indoor space that could have had a contact exposure. It could be placed in a classroom and then that could be indicative of what the teacher, as well as all the students, may have been exposed to for that period.”
The air sensor uses a polymer membrane made of polydimethylsiloxane, or PDMS, to collect aerosols and respiratory droplets (from coughing, sneezing, speaking, and breathing) that are present in the environment. The PDMS surface works a bit like flypaper to grab these droplets. The membrane is then sent off to the lab where any infectious cargo within the droplets can be analysed to measure how many RNA copies of SARS-CoV-2, the virus that causes covid-19, were present, providing a measure of the likely level of exposure.
The study, published in Environmental Science & Technology Letters, had members of the public including those who work in healthcare, homeless shelters, and restaurants wear the sampler to compare potential exposures in the community to exposures in specific work environments. The sampler was clipped to the shirt collar to capture the viral exposure in the ‘breathing zone’, close to the nose and mouth. After 5 days, the sampler was then returned to the lab where the PDMS membrane was processed by ddPCR: droplet digital PCR, which has a higher sensitivity compared to conventional quantitative PCR.
Results from the study were able to detect positive SARS-CoV-2 exposures at a measurement threshold of 6 RNA copies per sampler extraction - corresponding to the sampler ‘catching’ 14 RNA copies from the environment. This concentration is roughly 21 times lower than the estimated inhalation dose: the amount of virus needed to launch an infection.
But not all SARS-CoV-2 RNA will originate from an actively infectious virus. People who have been infected, but are no longer infectious, can shed inactive versions of the virus for quite a while. Krystal says distinguishing between infectious and inactive RNA copies is a natural extension of the study. “If we wanted to look at the viability of those RNA copies we could, because we are using this passive surface. We have deposition of those as aerosols and droplets on the surface of the film.” The researchers are also currently testing the ability of the sampler to detect other common viruses, such as rhinovirus and influenza.
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