Researchers have developed new flexible, porous, highly sensitive nitrogen dioxide sensors with potential applications in medical care, environmental health monitoring, and military use. These sensors can be attached to skin and clothing.
The team’s sensor designs, which improve on earlier models, and findings were published in ACS Applied Materials and Interfaces under the direction of Huanyu “Larry” Cheng, assistant professor of engineering science and mechanics at Penn State.
The sensors measure nitrogen dioxide from perspiration if they are implanted elsewhere on the body or from breath if they are attached under the nose. The direct skin attachment enables long-term, continuous gas monitoring as opposed to blood sampling.
Although similar sensors already exist, according to Cheng, the novel design’s breathability sets it apart.
“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 commonly used substrate materials for gas sensors are flexible, but not porous. 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.
Huanyu “Larry” Cheng
Block copolymers were combined with resin by Cheng and his team to create laser-written sensors with the necessary level of breathability.
“Block copolymer integration goes beyond the materials we have been using, so we explored extending the substrate material from the typical thin film to virtually anything,” Cheng said. “That can give us breathability and tunability of the pore size.”
According to Cheng, the sensor might keep an eye on illnesses like chronic obstructive lung disease, which nitrogen dioxide can aggravate. Additionally, he pointed out that although the sensors were created particularly to detect nitrogen dioxide, they may also be able to detect other gases and biomarkers, such as glucose levels to monitor diabetes or dangers in battle or industrial situations.
“The sensors can also be useful for monitoring gas in the environment,” he said. “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.”
Other authors on this paper are Li Yang, Huadong Ji, Chuizhou Meng, Guanhao Zheng, Xue Chen, Guangyu Niu, Jiayi Yan, Ye Xue, and Shijie Guo, all of Hebei University of Technology in Tianjin, China; and Yuhang Li of Beihang University in Beijing.
This research was supported by the National Science Foundation, the National Institutes of Health, Penn State, the Key Research and Development Project of Hebei Province, the National Natural Science Foundation of China, and the National Science Foundation.
