From outer space and down to nanotechnology

23 February 2011

Mysterious expanding ice crystals in the moons of Saturn and Neptune may be of interest to developers of microelectronics. Neutron scattering conducted at ISIS and the Institut Laue-Langevin (ILL) has discovered that methanol crystals that may be found in the outer solar system have unusual expansion properties. The finding by planetary geologist Dr. Dominic Fortes at UCL (University College London) is likely to be of interest to developers of nanoswitches.

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 spacecraft. 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.

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 nanoswitches 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, but scientists hope that better understanding of the phenomenon can bring forward potential technological applications.

“Currently, the use of NLC materials in technologies such as nanoswitches is purely theoretical and limited by our lack of understanding of the underlying physics”, says Professor Reinhard Neder, Chairman of the ILL crystallographic committee. “However, the simple structure of methanol monohydrate gives us a good chance to understand the source of this property and how to look for it in other more commercially viable materials.”

Dr. Fortes adds: “It was certainly unexpected. 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.”

Professor Richard Wagner, Director at the Institut Laue Langevin concluded: “This research is a good example of how even basic academic studies can have completely unpredictable benefits in other areas of science and technology.”

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