Researchers create tiny sensor using 'white graphene'

"There are only two or three institutions in the world that can produce single, two-dimensional layers of white graphite," said lead researcher Santiago J. Cartamil-Bueno.
By Brooks Hays   |   June 28, 2017 at 3:53 PM
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June 28 (UPI) -- Researchers have developed a new method for creating tiny mechanical sensors using "white graphene."

The sensor is made by placing white graphene, a 2D atomic sheet of hexagonal boron nitride, over the minuscule holes in a silicon substrate. Scientists say the material could serve as tiny gas and pressure sensors inside electronics.

The hexagonal structure of white graphene is similar to that of regular graphene, but the atomic layer is made up of boron nitride, the compound of boron and nitrogen, instead of carbon. Graphene is prized for its conductive qualities, but hexagonal boron nitride, or h-BN, works as an insulator.

White graphene is also more chemically and electrically stable than graphene, allowing it to function under more extreme circumstances, like in space.

Until, scientists have struggled to develop a scaleable way to make 2D layers of h-BN. Layers of graphene are easily exfoliated from graphite, but h-BN layers stick to one another.

"There are only two or three institutions in the world that can produce single, two-dimensional layers of white graphite, and the University of Cambridge is one of them," lead researcher Santiago J. Cartamil-Bueno said in a news release. "This project is a success thanks to our effective collaboration with them."

Cambridge scientists used a method called chemical vapor deposition to deposit single layers of hexagonal boron nitride on a sheet of iron foil.

Scientists at Delft University of Technology in the Netherlands used the white graphene layers from Cambridge to build the miniature sensors. By placing the white graphene over tiny cavities in a silicon substrate, researchers created tiny drums that work like mechanical resonators.

During the sensor-production process, scientists realized the drums were being contaminated by the polymer, making each drum-turned-sensor behavior slightly differently. Precision and consistency are essential to mechanical sensors. Researchers found that by treating the drums with ozone, they could rid the sensors of imperfections.

"Fortunately, this problem can be solved by only using organic substrates while transferring the sheet of white graphite onto the cavities," said Cartamil-Bueno.

Researchers detailed their breakthrough this week in the journal Nature. The next step is for scientist to incorporate the tiny sensors into actual electronics.

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