Material scientists in Switzerland have created a sensor that consists of a newly developed composite material that interacts with CO2 molecules and changes its conductivity depending on the level of CO2 in the environment. The sensor is able to pick up CO2 levels with a tiny chip that measures electrical resistance. Compared to current gas sensors, it is considerably smaller, simpler and requires less energy to operate.

The composite material itself is a polymer made of poly(ionic liquid)s (PIL). Past research from scientists worldwide shows that PIL can absorb CO2. This gave the scientists the basis for their idea.

“We asked ourselves if we could exploit this property to obtain information on the concentration of CO2 in the air and thereby develop a new type of gas sensor,” said Christoph Willa, a doctoral student at the Laboratory for Multifunctional Materials.

Willa and Dr. Dorota Koziej, who lead the experiment, discovered they could produce a composite by combining the PIL polymers with inorganic nanoparticles that also interact with CO2.

“Separately, neither the polymer nor the nanoparticles conduct electricity,” says Willa. “But when we combined them in a certain ratio, their conductivity increased rapidly.”

The scientists also discovered that the conductivity of the composite material at room temperature is CO2-dependent, making the new sensor much easier to use.

“Until now, chemoresistive materials have displayed these properties only at a temperature of several hundred degrees Celsius,” explains Koziej. That means most current sensors had to be heated to a high operating temperature beforehand. The new composite makes that process unnecessary.

Koziej believes that since the new composite can be applied to portable devices that measure air for scuba divers and extreme altitude mountaineers.

For more information, read When Nanoparticles Meet Poly(Ionic Liquid)s: Chemoresistive CO2 Sensing at Room Temperature at the Wiley Online Library.