This Flexible, Waterproof Gas Sensor Sits Under Your Nose for Health Monitoring, Disease Diagnosis

Designed like a sandwich and keeping moisture from wrecking the graphene layer, this sensor could provide large-scale health monitoring.

Researchers from Heibei University of Technology, the Tianjin Medical University General Hospital, Beihang University, and Pennsylvania State University have developed a stretchable, skin-friendly, waterproof sensor, which can be worn under the noise to analyze a patient's breath — built using laser-induced graphene.

"With this sensor, we are much closer to the actual application of helping a patient," claims paper co-author Li Yang, associate professor at Hebei University of Technology, of the team's work. "This sensor could be used for the early screening process, to make someone aware of the potential condition that may develop into a bigger concern later, and also for the existing COPD [Chronic Obstructive Pulmonary Disorder] or asthma patient to monitor the environment for potential exposure to nitrogen dioxide so they can take early prevention measures, like avoiding certain areas with higher nitrogen dioxide levels."

Building on earlier work led by co-author Huanyu "Larry" Chen at Pennsylvania State on the development of a waterproof temperature and motion sensor and a non-waterproof microscale gas sensor, the team were able to use laser-induced graphene (LIG) to build a functional gas sensor in a moisture-resistant membrane sandwich — allowing it to operate in humid environments, such as directly below a patient's nose so it can monitor their breath.

"Laser-induced graphene is hydrophilic, so it intrinsically is a water-absorbing material," Cheng explains. "Water will naturally get down into the material and change its properties. If you have water molecules absorbed by the sensor, that will change the response. By using a semi-permeable membrane with the LIG, we can block the water or moisture from the outside but still allow the permeation of the target gas molecule. Since the new material is stretchable and soft, it can be worn on the skin for a long time without causing irritation."

In testing on 30 individuals, the team found the prototype NOₓ wearable sensor performed well — reading values four times greater for COPD patients and those with asthma than those without, corresponding to higher amounts of nitrogen dioxide in their breath. "This could be used for a large-scale study to provide information that was previously inaccessible with the other type of sensor devices," Cheng proposes of the technology, "which is something I'm excited about."

The team's work has been published in the journal Microsystems & Nanoengineering under open-access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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