Sensors made from ‘frozen smoke’ can detect toxic formaldehyde in homes and offices

Researchers at the University of Cambridge developed sensors made from highly porous materials called aerogels. By precisely engineering the shape of the pores in the aerogels, the sensors were able to detect the fingerprint of formaldehyde, a common indoor air pollutant, at room temperature.

The proof-of-concept sensors, which require minimal power, can be adapted to detect a wide range of hazardous gases, and even miniaturized for wearable and healthcare applications. can go. gave Results It is reported in the journal Advances in science.

Volatile organic compounds (VOCs) are a major source of indoor air pollution, causing watery eyes, eye and throat irritation, and breathing problems at elevated levels. High concentrations can trigger attacks in people with asthma, and prolonged exposure can cause certain cancers.

Formaldehyde is a common VOC and is emitted from household items including pressed wood products (such as MDF), wallpapers and paints, and some synthetic fabrics. For the most part, the levels of formaldehyde emitted by these items are low, but levels can increase over time, especially in garages where paint and other formaldehyde-emitting products are most likely to be stored. .

As of 2019 Reports A fifth of UK households showed significant concentrations of formaldehyde, with 13% of homes exceeding World Health Organization (WHO) recommended levels, according to campaign group Clean Air Day.

“VOCs such as formaldehyde can cause serious health problems with prolonged exposure even at low concentrations, but current sensors do not have the sensitivity or selectivity to distinguish between VOCs that have different health effects,” said. Professor Tawfiq Hasan From Cambridge Graphene Centrewho led the research.

“We wanted to develop a sensor that is small and does not consume much power, but can selectively detect formaldehyde at low concentrations,” said Zhou Chen, first author of the paper.

The researchers based their sensor on aerogels: extremely light materials sometimes called ‘liquid smoke’, because they are more than 99% air by volume. The open structure of aerogels allows gases to move in and out easily. By precisely engineering the shape, or morphology, of the pores, aerogels can serve as highly efficient sensors.

Working with colleagues at the University of Warwick, the Cambridge researchers optimized the structure and composition of aerogels to increase their sensitivity to formaldehyde, making them filaments three times the width of a human hair. The researchers 3D printed lines of paste made from graphene, a two-dimensional form of carbon, and then freeze-dried the graphene paste to create holes in the final airgel structure. Aerogels also incorporate tiny semiconductors called quantum dots.

The sensors they developed were able to detect formaldehyde at concentrations as low as eight parts per billion, which is 0.4% of the level considered safe in UK workplaces. The sensors also work at room temperature, consuming very little power.

“Traditional gas sensors need to be heated, but because of the way we’ve engineered the material, our sensors work incredibly well at room temperature, so they’re much faster than other sensors. use 10 to 100 times less power,” Chen said.

To improve selectivity, the researchers then added machine learning algorithms to the sensor. Algorithms were trained to detect the ‘fingerprint’ of different gases, so that the sensor could distinguish formaldehyde’s fingerprint from other VOCs.

“Existing VOC detectors are blunt devices — you only get one number for the total concentration in the air,” Hassan said. “By creating a sensor that can detect specific VOCs at very low concentrations in real time, it can give home and business owners a more accurate picture of air quality and any potential health risks.”

The same technique could be used to develop sensors to detect other VOCs, the researchers say. In theory, a device the size of a standard household carbon monoxide detector could incorporate several different sensors, providing real-time information about a range of different hazardous gases. Co-author Professor Julian Gardner of the University of Warwick said, “At Warwick, we are developing a low-cost multi-sensor platform that will incorporate these new airgel materials and, combined with AI algorithms, detect various VOCs. Will put.”

“By using highly porous materials as sensing elements, we are opening up entirely new ways to detect hazardous materials in our environment,” Chen said.

Source: University of Cambridge