A flexible and implantable sensor that can monitor various forms of nitric oxide (NO) and nitrogen dioxide (NO2) gas is important because these gases can significantly impact human health. (Image: Penn State)

Sensors that monitor a patient’s condition during and after medical procedures can be expensive, uncomfortable, and even dangerous. Researchers have now designed a highly sensitive flexible gas sensor that can be implanted in the body and after it’s no longer needed, it safely biodegrades into materials that are absorbed by the body.

The sensor can monitor various forms of nitric oxide (NO) and nitrogen dioxide (NO2) gas in the body. Monitoring these types of gases is important because they can play either a beneficial or sometimes harmful role in human health.

Nitric oxide, which is produced naturally in the human body, plays an important role in health because it relaxes or widens blood vessels to enhance blood flow, allowing oxygen and nutrients to circulate through the body. On the other hand, exposure to nitrogen dioxide from the environment is linked to the progression of conditions such as chronic obstructive pulmonary disease. Nitric oxide is highly reactive and can be transformed into nitrogen dioxide when exposed to oxygen.

The team made the sensor from materials that are not just implantable, flexible, and stretchable but also biodegradable. While current devices are used outside of the body to monitor gas levels, they are bulky and potentially not as accurate as an implantable device. Implantable devices, however, need to be removed, which could mean another operation. The researchers investigated a design that does not need to be removed.

All of the components are biodegradable in water or in bodily fluids but remain functional enough to capture the information on the gas levels. In this case, the researchers made the device’s conductors — the elements that conduct electricity — out of magnesium and for the functional materials, they used silicon, which is also highly sensitive to nitric oxide.

The body can safely absorb all of the materials used in the device. An added benefit of the design is that the materials dissolve at a slow enough pace that would allow the sensors to function in the body during a patient’s recovery period.

Future work could look at designing integrated systems that could monitor other bodily functions for healthy aging and various disease applications.

For more information, contact Matt Swayne at This email address is being protected from spambots. You need JavaScript enabled to view it.; 814-863-6940.