World’s smallest NEMS sensor made from graphene

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Graphene, the “miracle material,” has become a talking point once again. This time, as a material for high-accuracy acceleration sensors in the nanometer range.

It’s fifteen years since Andre Geim and Konstantin Novoselov removed some graphene flakes from a lump of bulk graphite with sticky tape, for which they were subsequently awarded the Nobel Prize. What they discovered under the microscope has, since then, often been described as a “miracle material.” And not without good reason, as the perfect, two-dimensional, hexagonal lattice of carbon atoms is extremely light and transparent, stronger than steel and harder than diamond, but at the same time as flexible as rubber and it has amazing, almost resistance-free, electrical conductivity.

Consequently, it’s not really surprising that people soon believed that it had “futuristic” properties. Rollable mobile communication devices, airplanes as light as a feather, spaceships with solar cells, ultra-thin solar cells, and processors with mega clock speeds – when the tabloids get their hands on a story, nothing is impossible.

The chicken and the egg

However, it could take some time before much of this becomes reality. Also, because the chicken-egg problem tends to put a brake on innovative technologies that are especially dependent on a specific material. After all, production of a new raw material in sufficient quantities is usually very expensive at the start. But, at the same time, there is insufficient demand for the development of production plants that would solve the problem. Demand grows only when the material becomes less expensive.

As a result, the hype has calmed down a bit over the past years – but not the efforts of scientists to develop practical products from the findings of years of multi-billion-dollar basic research.

NEMS sensor made from graphene

For example, this includes the world’s smallest acceleration sensor. A team from the Royal Institute of Technology (KTH) in Stockholm, Sweden and the Aachen Graphene & 2D Materials Center – a consortium of RWTH Aachen University and AMO GmbH – used graphene in a nanoelectromechanical system (NEMS).

For several years, microelectromechanical systems (MEMS) have been responsible for innovations in sensor and medical technology. The next development stage now is nanoelectromechanical systems (NEMS). In combination with the incredible mechanical strength, the ultra-thin layer structure, and excellent conductivity of graphene, many new possibilities are opening up for extremely small acceleration sensors. Such as to optimize navigation in cell phones, to make mobile games more realistic, or to improve monitoring systems for cardiovascular diseases. They would also be conceivable in what are known as motion capture wearables, where they capture the tiniest movement of the human body.

The physical principle behind this is also well known. Due to the piezo-resistive effect, the material changes its resistance when it is subjected to pressure or expansion. This works extremely accurately even in this “atomic” magnitude.

In the last few years, scientists have proven the potential of graphene membranes for pressure and Hall sensors and for microphones. The range of applications is now augmented by acceleration sensors. To get the material ready for the market within a few years, the team is currently working on industry-compatible production and integration methods.

 

 

NEMS sensor (Image: KTH)

Tiny acceleration sensor made from graphene. (Image: KTH)