Accurate and continuous monitoring of nitrogen dioxide and other gases in humid environments is now possible, thanks to a new water-resistant gas sensor developed by Huanyu “Larry” Cheng, James L. Henderson Jr. Memorial Associate Professor of Engineering Science and Mechanics, and his team.
The sensor detects nitrogen dioxide in the breath, the concentration of which may indicate potential lung diseases, or in particular environments to monitor air quality. The team’s approach was published in Microsystems & Nanoengineering.
While Cheng had previously developed a waterproof sensor, this sensor could only detect temperature and motion. Cheng has also developed a highly customizable micro-scale gas sensor, as well as a versatile, porous and wise gas sensor. However, moisture, sweat or other moisture exposure would render the sensors unusable.
“We cannot avoid the humidity levels in the environment, that’s why we wanted to emphasize the moisture resistance property,” Cheng said.
Researchers used the same laser-induced graphene (LIG ) – a fast, cost-effective and environmentally friendly manufacturing method that uses laser writing to assemble two-dimensional layers of graphene – as they have done for previous gas sensors. This time, however, they also added a flexible elastomeric polymer substrate and a moisture-resistant semi-permeable membrane to either side of the LIG sensing layer.
“The Laser-induced graphene is hydrophilic, so it’s inherently a water-absorbing material,” Cheng said. “The water will naturally descend into the material and change its properties. If you have water molecules absorbed by the sensor, it will change the response. By using a semi-permeable membrane with the LIG, we can block water or moisture from the outside while allowing permeation of the target gas molecule. Since the new material is stretchy and soft, it can be worn on the skin for a long time without causing irritation.
To test the sensors, researchers have them used to assess the respiration of 30 individuals. They found that sensor response values were more than four times higher for people with chronic obstructive pulmonary disease (COPD) or asthma than for those without, meaning that people with people with COPD or asthma had more than four times the amount of nitrogen dioxide. in their exhalation.
“With this sensor, we are much closer to the real application of helping an individual,” said co-author Li Yang, associate professor at the School of Health Sciences and Biomedical Engineering, Hebei University of Technology. “This sensor could be used for the early screening process, to inform someone of the potential problem that could become a bigger concern later on, and also for the existing COPD or asthmatic patient to monitor the environment for exposure. potential to nitrogen dioxide so that they can take early preventive measures, such as avoiding certain areas where nitrogen dioxide levels are higher.”
Cheng said said that eventually this sensor could be used to monitor not only individual well-being, but also to better understand the health of a population.
“It could be used for a large-scale study to provide information that was previously inaccessible with the other type of sensor, which excites me,” he said.
Cheng is affiliated with the Resources Exploration Institute, the Institutes of Electrical power and the Envir onment, the Institute for Computational and Information Sciences, the University of Earth and Mineral Sciences, and several departments of the College of Engineering, all at Penn State.
The other authors of the article are Ye Xue from the School of Health Sciences and Biomedical Engineering of Hebei University of Technology in China Guanghao Zheng, Chuizhou Meng, Huadong Ji and Jiayi Yan from the School of Mechanical Engineering of the Hebei University of Technology in China Yaoqian Cao of Tianjin General Medical Hospital in China Yuhang Li of Beihang University in China Xue Cheng of School of Electrical Engineering of Hebei University of Technology and Guangyu Niu of the ‘School of Architecture and Art Structure of Hebei University of Technology.
The National Science Foundation, the National Institutes of Wellness, Penn Condition, the National Purely Natural Science Foundation of China and the Important Study and Advancement Task of Hebei Province funded this research.