The unexpected finding by planetary geologist Dr Dominic Fortes UCL (University College London) will interest developers of ‘nano-switches’ – single atom thick valves used in ‘micro-electronics’ at the nano scale.
Dr Fortes made the discovery whilst investigating the internal structure of icy moons, such as Neptune’s Triton, to explain the icy eruptions seen by passing space-craft. By studying the behaviour of methanol monohydrate, a known constituent of outer solar system ice, under conditions like those within the moons’ interiors he hoped to understand its role in volcanism.
Dr Fortes measured structural changes in methanol crystals over a range of temperatures and pressures. He found that when heated at room pressure they would expand enormously in one direction whilst shrinking in the other two dimensions. However when heated under an even pressure they expanded in two directions, whilst compressing in the third. This unexpected expansion (elongating and thinning) under uniform pressure is known as negative linear compressibility (NLC).
Whilst these results form the next step towards understanding outer solar system volcanic activity, Fortes’ discovery is of significant interest for material scientists developing nanotechnology. The predictable expansion of NLC materials in a particular direction under pressure makes them a good candidate for nano-switches where their shape-shifting properties can be used like a microscopic, pressure-controlled valve directing the flow of electricity.
NLC materials are extremely rare with only around 15 known examples. What causes this property is still relatively unknown. Scientists hope better understanding of the phenomenon can bring forward potential technological application.
The use of NLC materials in technologies such as nano-switches is currently purely theoretical, and is limited by a lack of understanding of the underlying physics involved. However, the simple structure of methanol monohydrate gives scientists a good chance to understand the structure of this property. It also could help scientists understand how to look for more commercially viable NLC materials.
“It was certainly unexpected,” explains Dr Fortes. “As a planetary geologist my focus is understanding the mechanisms behind volcanic eruptions in the outer solar system. If my results open doors for more applied science back on Earth, that’s a bonus.”
Dominic Fortes
Research date: January 2009
Further Information
Contact: Dr AD Fortes andrew.fortes@ucl.ac.uk
Further information: AD Fortes et al, Science, (2011):
Vol. 331 no. 6018 pp. 742-746
