Medical & Dental

3D printing-enhanced ‘eNose’ trained to ‘sniff-out’ COVID-19 in just 80 seconds

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Scientists at the Israeli Weizmann Institute of Science have 3D printed an ‘electronic nose’ accessory that enables it to safely ‘smell’ chemicals which identify people as being infected with COVID-19. 

The team’s instrument, featuring a gas unit, sensor array and 3D printed sampling valve, has been trained through practical testing to find COVID-19 and other volatile organic compounds (VOCs) inside patients’ nasal passages. With further R&D, the scientists believe that their device could help broaden the scale of COVID-19 testing, and expedite the process as airports and live events now begin to reopen. 

“Every disease has an odour,” the project’s leader Noam Sobel explained during early testing last year. “This is because diseases change metabolic processes which have metabolites, and these have a smell.”

“We have in our lab, a device referred to as an ‘electronic nose,’” he added. “It’s a sensitive device that generates a pattern, reflecting every odorant it smells, so we decided to use it to see if we could characterize the smell of COVID-19.”

“We’re gaining information that may open a path towards rapid diagnostics.”

The scientists' 3D printing-optimized eNose being used during COVID-19 testing.
The scientists’ 3D printing-optimized eNose being used during COVID-19 testing. Image via the Plos One journal.

‘Sniffing-out’ signs of COVID-19 

Although viruses alone don’t emit VOCs, they can cause infected human cells to do so, hence many diseases can actually be detected by smell. As a result, trained animals such as dogs can currently be deployed to identify signs of illness within apparently healthy individuals, but accomplishing this at scale has so far proven problematic. 

Electronic noses, meanwhile, contain multiple sensors that can be optimized for detecting signals at different chemical ranges, and trained to mimic the animal olfactory system. However, developing a multi-sensor pattern that’s able to target certain VOCs is time-consuming, and the team began tweaking their ‘nose’ for COVID-19 detection at the disease’s outbreak, when time was of the essence. 

What’s more, the scientists’ device was at that point lab-based, meaning that they needed to adapt it for off-site applications. To achieve this, the researchers decided to 3D print a novel sampling device, before rapidly getting it approved by the Israeli Ministry of Health and working with Magen David Adom (MADA) to trial their enhanced electronic nose in the field at a drive-through testing center. 

The Israeli scientists' 3D printed sampling valve.
The Israeli scientists’ 3D printed sampling valve. Image via the Plos One journal.

Field-testing the upgraded ‘eNose’

As a basis for their experiments, the scientists used an AIRSENSE PEN3 eNose, which includes ten different thermo-regulated metal oxide sensors as standard, enabling it to ‘sense’ COVID-19. Later, in order to prevent backflow, and people accidentally becoming infected after repeated testing, the team opted to fit their PEN3 with a 3D printed one-way flow valve. 

Designed using CAD software, the researchers’ sampling device was built to fit snugly against the’ nostril from which it pulled air, and provide test subjects with an extra layer of protection against device breakdown. In practise, at MADA’s testing clinic in Tel Aviv, the team’s eNose was applied over the course of 22 days by different patients for eighty seconds each, before taking a normal PCR test. 

The resulting data was then repeatedly run through Mathworks’ Matlab software, using a deep learning algorithm to ‘train’ the scientists’ device to identify the VOC differences between positive and negative tests, ultimately managing to achieve a mean ‘true positive’ rate of around 66.7%, and a ‘false positive’ result of 57%.  

Although the Israeli team concluded by admitting that they haven’t yet identified the precise “molecular identity” of the COVID-19 signal, and that their device returned a very high level of false positives, they maintain that these errors were caused by “olfactory noise,” and that a fully-optimized eNose could still be applied to help the world reopen post-pandemic. 

3D printed COVID-19 testing devices

Since the pandemic’s global outbreak last year, researchers have deployed a wide variety of 3D printing techniques to produce experimental COVID-19 testing kits. Scientists at Carnegie Mellon University (CMU) have used Optomec’s Aerosol Jet Printing (AJP) process to create a novel 3D printed sensor that’s capable of rapidly detecting COVID-19 antibodies. 

Researchers at Wageningen University, meanwhile, have taken an ultra-low-cost approach, turning recycled coffee capsules into COVID-19 tests that can be assembled at home for less than 20p. By fitting their pods with 3D printed vial holders, the team were able to convert them into mini ‘chemical reactors,’ which heat up to reveal whether or not a patient is infected. 

Elsewhere, 3D printing service provider PrintParts has helped to meet COVID-19 testing demand by expanding its supply chain to mass-produce nasopharyngeal (NP) swabs. At the height of the pandemic last year, the company opened a new production lab in Manhattan, which enabled it to produce large quantities of swabs for use in New York City. 

The researchers’ findings are detailed in their paper titled “Proof of concept for real-time detection of SARS CoV-2 infection with an electronic nose.” The study was co-authored by Kobi Snitz, Michal Andelman-Gur, Liron Pinchover, Reut Weissgross, Aharon Weissbrod, Eva Mishor, Roni Zoller, Vera Linetsky, Abebe Medhanie, Sagit Shushan, Eli Jaffe and Noam Sobel. 

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Featured image shows the scientists’ 3D printing-optimized eNose being deployed during COVID-19 testing. Image via the Plos One journal.

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