Experts at the University of Sheffield have created an `artificial muscle´ reaction in materials that respond to chemical vapours, something that could pave the way for a new type of gas sensor.

Researchers found they could manipulate molecules by exposing them to an acidic vapour - which caused them to expand - or contract them when put into contact with ammonia.

The work was a collaboration by academics from across the University´s Faculty of Science, including Dr Tim Richardson and Dr Stu Brittle from the Department of Physics and Astronomy, Dr Alan Dunbar from the Department of Chemical and Biological Engineering and Professor Chris Hunter of the Department of Chemistry.

Dr Tim Richardson said: "Imagine a coffee table stood up on its end, rather than as normal with its legs down. Its footprint on the floor would be much smaller than its footprint when in the normal position. If the table was put back to its normal state, then its foot print would increase.

"Now imagine a room with the floor half covered in coffee tables, all stood on their ends and packed closely together. If something triggered them all to return to their normal position, then the floor would be filled, or more than filled, due to the expansion of their footprint. If this happens on a molecular scale, you have the possibility of creating molecular systems that can expand and contract, like artificial muscle.

"A practical application for this is a gas sensor although stimulus-response molecular systems in general have lots of interest academically too for understanding how to control the behaviour of molecules. Other applications could chemically triggered pumps and artificial muscle models to learn more about how mechanical shape change and expansion can be related to chemical interaction processes."

The scientists found the molecules reacted to several different gases including hydrogen chloride, which is used in industry, toxic nitrogen dioxide, organic acids, and ammonia, which is used in cleaning products and as a fertiliser.

The `expansion - contraction´ research began 18 months ago as a side-line from another Engineering and Physical Science Research Council (EPSRC) project which started about three years ago.