Scientists have developed a highly sensitive, wearable gas sensor which may help monitor environmental pollutants, and detect biomarkers for medical conditions.
The device, that may soon become commercially available, is an improvement on existing wearable sensors because it uses a self-heating mechanism that enhances sensitivity, the researchers said.
This allows for quick recovery and reuse, unlike other devices of this type which require an external heater, according to the study published in the Journal of Materials Chemistry A.
"People like to use nanomaterials for sensing because their large surface-to-volume ratio makes them highly sensitive," said Huanyu Cheng, an assistant professor at the Pennsylvania State University in the US.
"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 inter-digitated electrodes, which are like the digits on your hand," Cheng said in a statement.
The researchers used a laser to form a highly porous single layer of nanomaterial, similar to graphene, for sensors that can detect gas, and biomolecules.
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In the non-sensing portion of the device, the team created a series of layers that they coated with silver.
On applying an electrical current to the silver, the gas sensing region locally heats up due to significantly larger electrical resistance, eliminating the need for a separate heater.
The nanomaterials used are reduced graphene oxide, and molybdenum disulfide, or a combination of the two, the researchers said.
The materials may also be made of a metal oxide composite consisting of a core of zinc oxide and a shell of copper oxide, they said.
"Using a carbon dioxide (CO2) laser, often found in machine shops, we can easily make multiple sensors on our platform," Cheng said.
"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," he said.
An unnamed medical device company is working with the team to scale up production for patient health monitoring, including gaseous biomarker detection from the human body, and environmental detection of pollutants that can affect the lungs.
"We showed that we could detect nitrogen dioxide, which is produced by vehicle emissions," said Ning Yi, a doctoral student in Chen's lab.
"We can also detect sulphur dioxide, which, together with nitrogen dioxide, causes acid rain. All these gases can be an issue in industrial safety," Yi said.
The researchers said their next step is to create high-density arrays to improve the signal, and make the sensors more selective.
This may involve using machine learning, a form of artificial intelligence (AI), to identify the distinct signals of individual molecules on the platform, they said.