New wearable nitrogen dioxide sensors could improve air quality monitoring

Researchers have developed flexible, porous and highly sensitive nitrogen dioxide sensors that can be applied to skin and clothing, in a breakthrough for air quality monitoring.

The sensors monitor nitrogen dioxide, either from breath if attached under the nose or from perspiration elsewhere on the body, allowing for continuous long-term monitoring of the air pollutant.

The researchers explain that the sensor could monitor conditions such as chronic obstructive pulmonary disease – which nitrogen dioxide can cause or make worse – and could potentially detect a variety of pollutants and biomarkers, such as industrial hazards or glucose levels to monitor diabetes.

‘The sensors can also be useful for monitoring gas in the environment,’ said Assistant Professor of Engineering Science and Mechanics at Penn State, Huanyu Cheng, who led on the design. ‘We could monitor air quality and inform patients of potential concerns about too much exhaust from cars, for example. Then, they could use that information to avoid certain areas on certain days.’

Cheng explains that while similar sensors exist, a key differentiator of the new sensor is breathability.

‘The commonly used substrate materials for gas sensors are flexible, but not porous,’ he said. ‘The accumulation of water moisture from the skin surface can potentially lead to irritation or damage to the skin surface. We need to make sure the device can be porous so that moisture can go through the sensor without accumulation on the surface.’

The researchers created the new sensors using a fabrication method known as laser direct writing.

‘Laser direct writing is similar to additive manufacturing in that it is easy to set up and low cost, and the laser is widely available,’ Cheng said. ‘The process is relatively robust, rapid and could be scaled up to large-scale manufacturing production.’

The researchers published their sensor designs and results in ACS Applied Materials and Interfaces.

Photo by Matt Boitor