Computers in the future will be grown in jars, not assembled in a factory. A major step towards this goal has been achieved through collaborative research by scientists at University College Dublin and the University of California, Los Angeles.
"The future will see complex structures being built in solution by programmed construction," said Dr Donald Fitzmaurice, director of the nanochemistry group at UCD. He said this involved learning how to build complex molecular structures attached to a crystalline surface.
UCD and UCLA teams have done just that, attaching a two-part rod and piston structure, produced by UCLA, to a gold crystal produced by UCD, which "assembled" the final structure.
The work, done in collaboration with the supra-molecular chemistry group at UCLA under Prof Fraser Stoddart, is published today in the leading chemistry journal, Angewandte Chemie International Edition. It provides the journal's cover story and the accompanying illustration, produced by UCD campus company Cell Mark Ltd, was on its cover.
"We have taken a classical motif from chemistry, the rod and piston, and attached it to the surface of a nanocrystal. It brings together two strands of chemistry," he said. Complex molecular architecture has been joined to a nanocrystal foundation.
One would not be useful without the other in the context of a working device, he said. The ring and piston chemical structure would act as a molecular switch in a future device. The nanocrystal would give the switch "access to the real world", a way for information to move back and forth between more conventional electronics and the switch.
The molecular machine described in the report was not a working device, he pointed out. "It is a signpost for the future. It shows that this can be done." It meant, however, that researchers continuing work towards an ultra-small molecular computer now "have a bigger Lego set" to use as they link molecular structures.
There were two key aims, he said, "how to increase the functional diversity, getting the function you want rather than the function you have to put up with" in such a device, and "how to interface the nanoscale world to the macroscopic world".
The size of the components used in this molecular machine is almost beyond comprehension. They are measured in nanometres, which is a billionth of a metre or a millionth of a millimetre. A penny is about a millimetre thick.
A typical nanocrystal would measure from one to 100 nanometres, Dr Fitzmaurice said, and the pure gold nanocrystals used in the research measured about four nanometres. This would be one 250,000th of the thickness of a penny.
The "working" part of the assembly has an electron-rich ring-shaped receptor molecule and an electron-poor, rod-shaped molecule. The rings are "crown ethers", loops of carbons and oxygens, and the rods are two joined benzene rings. The rings are fixed to the gold nanocrystal via a sulphur atom link.
The rods are attracted to the rings because of their opposing electrical charges. These links could be made more specific by modifying the construction of the various components, Dr Fitzmaurice said. Commenting on the significance of the work, he said: "It is a lot and it is not."
Dr Fitzmaurice praised the work of two women who were central to the success of the research, Dr Nelsi Zaccheroni in UCD and Dr Sabine Wenger in UCLA.