Gravimetric sensors to improve greenhouse gas detection

Scientists from Kaunas University of Technology (KTU) have developed so-called gravimetric sensors that can detect greenhouse gases such as carbon dioxide, methane and others. The researchers believe their sensors, which won the Sails of Europe 2023 award “For Investment in Innovation in Business”, are a good alternative to electrochemical sensors currently in use, as they are more sensitive and use less energy.

Led by Dr Darius Viržonis, the scientists came up with an idea to apply a certain measurement principle — gravimetry — to the development of the sensors. Gravimetry is based on changes in the oscillation frequency of the sensing elements in sensors that measure air pollution and also indicate a change in mass, which allows the detection of bound substances and specific molecules.

As explained by Viržonis, the new sensors work based on capacitive micromachined ultrasonic transducers (CMUTs). “This is a way to make arrays of microscopic-sized cells that vibrate at a frequency of several million times per second,” he said. “As the vibrating elements are very small, their moving mass is also small, which makes them very sensitive to external objects attaching to their surface.”

Focusing their research on the environment, the team decided to use the sensors to record greenhouse gases such as carbon dioxide, methane, water vapour, sulfur dioxide, nitrogen oxides and diesel fuel molecules. According to Viržonis, the technology offers a wide range of possibilities for detecting biological pollution and can even detect virus DNA.

Discussing contemporary technologies, Viržonis noted that the majority of the market is still occupied by electrochemical gas sensors, which do not meet the requirements of the growing safety and environmental standards. “Gravimetric gas sensors … have the potential to replace many of the electrochemical sensors currently in use, as they have higher sensitivity, better selectivity, interact with different gases and consume significantly less energy,” he said.

One of the advantages of the sensors is due to their small size, according to Viržonis. He explained, “Our sensors can in a way be seen as scales weighing molecules. If you make the scales very small, you not only increase their sensitivity and accuracy but also reduce their cost and energy requirements. This creates the technological prerequisites to have more functionality at the same price or maybe even cheaper.”

According to Viržonis, if air quality or pollution measurement devices become widely available in terms of cost and functionality, technical preconditions for better control of anthropogenic greenhouse gas emissions will be created. “If this control is ensured, we will all live under cleaner air, we will have more biodiversity and perhaps we will be able to reclaim the territories in East Asia that have already been practically lost to humanity due to air pollution,” he said.

Viržonis added that the project will be particularly useful for future health research, as the same technological basis could allow for the development of more versatile and sensitive tools for the diagnosis of viral diseases. The scientists have now begun work on launching a startup company, Orius, whose task is to find the right niches and the right users for the new sensors.

“Gravimetric gas sensors are an innovation, and we are delighted that our prototypes are already attracting interest from potential users,” Viržonis said.