By Jonathan Fildes
Science and technology reporter, BBC News
The researchers have already built larger 'brains'
A tiny chemical "brain" which could one day act as a remote control for swarms of nano-machines has been invented.
The molecular device - just two billionths of a metre across - was able to control eight of the microscopic machines simultaneously in a test.
Writing in Proceedings of the National Academy of Sciences, scientists say it could also be used to boost the processing power of future computers.
Many experts have high hopes for nano-machines in treating disease.
"If [in the future] you want to remotely operate on a tumour you might want to send some molecular machines there," explained Dr Anirban Bandyopadhyay of the International Center for Young Scientists, Tsukuba, Japan.
"But you cannot just put them into the blood and [expect them] to go to the right place."
Dr Bandyopadhyay believes his device may offer a solution. One day they may be able to guide the nanobots through the body and control their functions, he said.
"That kind of device simply did not exist; this is the first time we have created a nano-brain," he told BBC News.
The machine is made from 17 molecules of the chemical duroquinone. Each one is known as a "logic device".
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They each resemble a ring with four protruding spokes that can be independently rotated to represent four different states.
One duroquinone molecule sits at the centre of a ring formed by the remaining 16. All are connected by chemical bonds, known as hydrogen bonds.
The state of the control molecule at the centre is switched by a scanning tunnelling microscope (STM).
These large machines are a standard part of the nanotechnologist's tool kit, and allow the viewing and manipulation of atomic surfaces.
Using the STM, the researchers showed they could change the central molecule's state and simultaneously switch the states of the surrounding 16.
"We instruct only one molecule and it simultaneously and logically instructs 16 others at a time," said Dr Bandyopadhyay.
The configuration allows four billion different possible combinations of outcome.
The two nanometre diameter structure was inspired by the parallel communication of glial cells inside a human brain, according to the team.
To test the control unit, the researchers simulated docking eight existing nano-machines to the structure, creating a "nano-factory" or a kind of "chemical swiss army knife".
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The attached devices, created by other research groups, included the "world's tiniest elevator", a molecular platform that can be raised or lowered on command.
The device is about two and a half nanometres (billionths of a metre) high, and the lift moves less than one nanometre up and down.
All eight machines simultaneously responded to a single instruction in the simulation.
"We have clear cut evidence that we can control those machines," said Dr Bandyopadhyay.
This "one-to-many" communication and the device's ability to act as a central control unit also raises the possibility of using the device in future computers, he said.
Machines built using devices such as this would be able to process 16 bits of information simultaneously.
Current silicon Central Processing Units (CPUs) can only carry out one instruction at a time, albeit thousands of times per second.
The researchers say they have already built faster machines, capable of 256 simultaneous operations, and have designed one capable of 1024.
However, according to Professor Andrew Adamatzky of the University of the West England (UWE), making a workable computer would be very difficult at the moment.
"As with other implementations of unconventional computers the application is very limited, because they operate [it] using scanning tunnel microscopy," he said.
But, he said, the work is promising.
"I am sure with time such molecular CPUs can be integrated in molecular robots, so they will simply interact with other molecular parts autonomously."