New wearable vapour sensor for disease monitoring

Researchers, including one of Indian-origin, are developing a new wearable vapour sensor that could offer continuous disease monitoring for patients with diabetes, high blood pressure, anemia or lung disease.
The new sensor, being developed at the University of Michigan, can detect airborne chemicals either exhaled or released through the skin.
It would likely be the first wearable to pick up a broad array of chemical, rather than physical, attributes, researchers said.
"Each of the diseases has its own biomarkers that the device would be able to sense. For diabetes, acetone is a marker, for example," said Sherman Fan, a professor of biomedical engineering.

Other chemicals it could detect include nitric oxide and oxygen, abnormal levels of which can point to conditions such as high blood pressure, anemia or lung disease.
Fan is developing the sensor with Zhaohui Zhong, an associate professor of electrical and computer engineering, and Girish Kulkarni, a doctoral candidate in electrical engineering.

The researchers said their device is faster, smaller and more reliable than its counterparts, which today are much too big to be wearable.
Beyond disease monitoring, the sensor has other applications. It would be able to register the presence of hazardous chemical leaks in a lab, or elsewhere, or provide data about air quality.

To create their technology, the researchers took a unique approach to detecting molecules.
"Nanoelectronic sensors typically depend on detecting charge transfer between the sensor and a molecule in air or in solution," Kulkarni said.
However, these previous techniques typically led to strong bonds between the molecules being detected and the sensor itself. That binding leads to slow detection rates.
"Instead of detecting molecular charge, we use a technique called heterodyne mixing, in which we look at the interaction between the dipoles associated with these molecules and the nanosensor at high frequencies," Kulkarni said.
This technique, made possible through the use of graphene, results in extremely fast response times of tenths of a second, as opposed to the tens or hundreds of seconds typical in existing technology.

It also dramatically increases the device's sensitivity. The sensor can detect molecules in sample sizes at a ratio of several parts per billion.
These nanoelectronic graphene vapour sensors can be completely embedded in a microgas chromatography system, which is the gold standard for vapour analysis, the researchers said.