Engineers have created a nanomaterial that breaks records by expanding sideways when stretched in one direction. Stretching a balloon is a trick to make it easier to inflate, but when the balloon is stretched, its width shrinks. However, PhD student Noah Stocek, working with physicist Giovanni Fanchini at Western University, has developed a new nanomaterial that does the opposite. They conducted their work at Interface Science Western, which is home to the Tandetron Accelerator Facility.A team of scientists has developed thin layers of tungsten semi-carbide (W2C), which is made up of equal parts of tungsten and carbon atoms. These nanosheets have a unique property: when they are stretched in one direction, they expand in the perpendicular direction. This type of structural design is called auxetics.
What makes these nanosheets special is that their structure is not flat. Instead, they are made up of repeating units that consist of two tungsten atoms for every carbon atom. These units are arranged in a way that resembles the dimpled surface of an egg carton. When tension is applied to the elastic nanosheet in one direction, it expands in the other direction due to the presence of these dimples.
The previous material that could only expand by 10 percent per unit length has been surpassed by the Western-engineered tungsten semi-carbide nanosheet, which can expand to 40 percent, setting a new world record. According to Stocek, the goal was to create a two-dimensional nanomaterial from tungsten semi-carbide, which had been predicted by theorists in 2018 but had not been successfully developed until now despite numerous attempts by research groups worldwide.
Constructing the new tungsten semi-carbide was previously not possible.The researchers Stocek and Fanchini turned to plasma physics to create the single atom layers of nanomaterial, avoiding the use of chemical methods. Plasma, which is made of charged particles of atoms, is the fourth state of matter (along with solid, liquid, and gas). It is found in natural phenomena like the northern lights and the Sun’s corona during a solar eclipse, as well as in everyday items such as neon lighting, fluorescent tubes, and flat-screen TVs.
Conventionally, special furnaces are used to produce two-dimensional nanomaterials by heating gases at high temperatures to chemically react and form the desired substance. This approach was not suitable for creating the nanomaterial in this case, so the researchers turned to plasma physics instead.The previous approach proved to be ineffective because any chemical reaction, the most common process, would result in a product that is different from the desired nanomaterial.
“That’s where most researchers who attempted to obtain this material before us encountered difficulties, so we had to change direction,” stated Fanchini.
Instead of using furnaces to heat a gas containing tungsten and carbon atoms, which would produce neutral particles like those found in solids, liquids, or gases, Stocek and Fanchini developed a new custom instrumentation that generates a plasma consisting of electrically charged particles.
Objectives
W2C nanosheets have a wide range of potential applications, starting with a novel strain gauge. These gauges are commonly used to measure expansion and stretch in various objects, such as airplane wings and household plumbing.
For example, if you are concerned about the possibility of a pipe in your home deforming and potentially bursting, you could attach a sensor made from this two-dimensional nanomaterial to the pipe. Then, you could use a computer to monitor the current flowing through it. An increase in current would indicate that the pipe is expanding and at risk of bursting, according to Stocek.
In reality, the new nanomaterial has even greater potential than that.The nanomaterial is electrically conductive, allowing for various applications such as sensors and stretchable electronics. This new material eliminates the need to rely on changes in material thickness to carry a current, opening up endless possibilities for its use in different devices.Reference
Noah B. Stocek, Farman Ullah, Giovanni Fanchini. Giant Auxetic Behavior in Remote-plasma Synthesized Few-Layer Tungsten Semicarbide. Materials Horizons, 2024; DOI: 10.1039/D3MH02193A