Piezoresistor the size of a single molecule

A team of researchers led by Dr Nadim Darwish from Curtin University, Professor Jeffrey Reimers from the University of Technology Sydney, Associate Professor Daniel Kosov from James Cook University, and Dr Thomas Fallon from the University of Newcastle, have developed a piezoresistor that is reportedly about 500,000 times smaller than the width of a human hair.

According to Kosov, piezoresistors are commonly used to detect vibrations in electronics and automobiles, such as in smartphones for counting steps, and for airbag deployment in cars. Darwish said they have developed a more sensitive, miniaturised type of this key electronic component that transforms force or pressure into an electrical signal and is used in many everyday applications.

Darwish believes that the new type of piezoresistor will open up a new realm of opportunities for human–machine interfaces, due to its size and chemical nature. “As they are molecular-based, our new sensors can be used to detect other chemicals or biomolecules like proteins and enzymes, which could be game-changing for detecting diseases,” Darwish said.

Fallon said the piezoresistor was made from a single bullvalene molecule that, when mechanically strained, reacts to form a new molecule of a different shape, altering electricity flow by changing resistance. According to Fallon, the different chemical forms are known as isomers. “This is the first time that reactions between them have been used to develop piezoresistors. We have been able to model the complex series of reactions that take place, understanding how single molecules can react and transform in real time,” Fallon said.

Reimers said the significance of this is the ability to electrically detect the change in the shape of a reacting module, back and forth, at approximately every one millisecond. Kosov said understanding the relationship between molecular shape and conductivity could enable researchers to determine the basic properties of junctions between molecules and attached metallic conductors. “This new capability is critical to the future development of all molecular electronics devices,” Kosov said.

The research findings were published in the journal Nature Communications.

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