A Japanese research team has developed a nano-mesh electrode that is light in weight and thin and does not cause inflammation even after being attached to human skin for a long time.

The team was led by Takao Someya, professor at the School of Engineering, the University of Tokyo. It developed the electrode in cooperation with Masayuki Amagai, professor at the Graduate School of Medicine, Keio University, Riken and Japan Science and Technology Agency (JST).

The nano-mesh electrode can be used as a sensor electrode for measuring biological information for a long period of time in the fields of healthcare, medicine, nursing, etc. The team has already confirmed that it is possible to use the electrode to measure myoelectricity, temperature, pressure and so forth. The results of the research were published on the website of the Nature Nanotechnology magazine July 17, 2017 (the UK time).

The team led by Someya has been engaged in the development of a light-weight, thin biosensor that can be attached to human skin without causing discomfor. However, what the team has developed so far has a low breathability. When it is attached to human skin for a long time, it can cause inflammation, resulting in inching and reddish skin.

On the other hand, the new nano-mesh electrode has a high breathability and does not prevent cutaneous (dermal) respiration.

"We have removed negative elements, namely inflammatory reaction (from a biosensor to be attached to human skin)," Someya said. "We can now use it for experiments (for measuring biological information) at ease."

The newly-developed nano-mesh electrode was made by using the "electro-spinning" method to form nanofiber-like polyvinyl alcohol and vapor-depositing gold on its surface. With its nano-size mesh structure, it has a high breathability and a moisture vapor transmission rate of 96.5%.

When the sheet-like electrode is placed on human skin and a small amount of water is sprayed on it, the polyvinyl alcohol melts and sticks to the skin, forming metal electrodes along the uneven skin surface. Also, it can be easily removed from the skin by, for example, rubbing it.

To examine whether the nano-mesh electrode causes inflammatory reaction on skin, the research team conducted a patch test on 20 subjects. In the test, one week after silicon and parylene were attached to skin in addition to the nano-mesh electrode, the condition of the skin was examined by dermatologists. This test was carried out mainly by Amagai.

As a result, it was found that silicon and parylene caused a light inflammatory reaction but no inflammatory reaction was found on the skin under the nano-mesh electrode. Also, according to the questionnaires about discomfort, itching, reddish skin, etc, the nano-mesh electrode caused the least discomfort.

The research team also confirmed that the nano-mesh electrode can actually measure biological information. When the electrode was attached to an arm to measure myoelectricity, it was measured with a signal/noise ratio equivalent to that of measurement conducted with a conventional gel electrode.

Furthermore, the team combined the nano-mesh electrode with a wireless unit, sensor device, etc and succeeded in measuring temperature, pressure and change in resistance at the time of attaching it to (and detaching it from) a metal object.

Even when the nano-mesh electrode is expanded and contracted along with skin movements, it does not lose its electric conductivity. Its resistance value hardly changed even after being expanded/contracted 10,000 times on the skin.