Jan 17 2020
According to scientists at Northeastern University and Penn State, a new wearable and highly sensitive gas sensor for monitoring human health and the environment may soon be available on the market.
A wearable gas sensor can monitor environmental and medical conditions. Image: Credit: Cheng Lab/Penn State.
The latest sensor device is an advancement of current wearable sensors because it utilizes a self-heating mechanism that improves sensitivity. It enables reuse and rapid recovery of the device, but other types of similar devices need an external heater. Moreover, other wearable sensors need a costly and time-intensive lithography process under cleanroom settings.
People like to use nanomaterials for sensing because their large surface-to-volume ratio makes them highly sensitive. The problem is the nanomaterial is not something we can easily hook up to with wires to receive the signal, necessitating the need for something called interdigitated electrodes, which are like the digits on your hand.
Huanyu Cheng, Assistant Professor, Departments of Engineering Science and Mechanics and Materials Science and Engineering, Penn State
With the help of a laser, Cheng and his research team pattern a single line of highly porous nanomaterial. This nanomaterial is analogous to graphene-based sensors that detect biomolecules, gas, and, in the days to come, chemicals.
Within the non-sensing part of the device platform, the researchers produced a sequence of serpentine lines that were coated with silver. As soon as electrical current is applied to the silver, the gas sensing area heats up locally because of the considerably greater electrical resistance. Therefore, the need for a separate heater is eliminated.
The serpentine lines enable the sensor device to stretch, just like springs, to adapt to the body’s flexing movement for wearable sensors.
In this study, the nanomaterials utilized were molybdenum disulfide and reduced graphene oxide, or a combination of both; or a metal oxide composite containing a shell of copper oxide and a core of zinc oxide, denoting the two groups of gas sensor materials that are extensively used—low-dimensional nanomaterial and metal oxide nanomaterial.
Using a CO2 laser, often found in machine shops, we can easily make multiple sensors on our platform. We plan to have tens to a hundred sensors, each selective to a different molecule, like an electronic nose, to decode multiple components in a complex mixture.
Huanyu Cheng, Assistant Professor, Departments of Engineering Science and Mechanics and Materials Science and Engineering, Penn State
This wearable sensor has captured the attention of the U.S. Defense Threat Reduction Agency that wanted to detect biological and chemical agents. These agents can potentially damage the lungs or nerves, stated the scientists.
In addition, a medical device firm is working with the researchers to expand production for patient health monitoring, such as the detection of environmental pollutants that can damage the lungs and the detection of gaseous biomarkers from the human body.
In this paper, we showed that we could detect nitrogen dioxide, which is produced by vehicle emissions. We can also detect sulfur dioxide, which, together with nitrogen dioxide, causes acid rain. All these gases can be an issue in industrial safety.
Ning Yi, Study Co-Lead Author, Department of Materials Science and Engineering, Penn State
The article was posted online in the Journal of Materials Chemistry A. Yi is a doctoral student in Chen’s laboratory.
According to the scientists, the next step is to develop arrays of high density and try out some concepts to enhance the signal and render the sensors more selective. Such a process may involve the use of machine learning to detect the clear signals produced by individual molecules on the device platform.
The journal’s upcoming print version will feature this article with the image of the researcher printed on its back cover.
Other authors of the study titled “Novel gas sensing platform based on a stretchable laser-induced graphene pattern with self-healing capabilities” include Li Yang, co-first author and visiting scientist, and Jia Zhu, a doctoral student in Cheng’s team.
Other study authors include Hongli Zhu, an assistant professor from Northeastern University as well as her student Zheng Cheng; and Xueyi Zhang, an assistant professor of chemical engineering and his doctoral student Xinyang Yin from Penn State. A provisional patent on this work has been applied by the scientists.
The study was supported by seed grants and start-up funding at Northeastern University and Penn State, and also by the National Science Foundation.