Scientists in the US may have paved the way towards working molecular computers.

A group of researchers at Bell Labs have made tiny functioning transistors a million times smaller than a grain of sand.

Making large quantities of the tiny components should be straightforward because they self-assemble.

But researchers caution that it could be years before such small components find their way into commercial devices or desktop computers.

Bulk bits and bytes

The biggest improvements in the processing power of a chip have come from shrinking the components that make up the device.

The first transistor was roughly 2.5 centimetres (one inch) across and now it is possible to cram more than a billion of them on to a single chip.

Silicon chips use transistors to form the underlying logic of the processor and as storage for memory.

Scientists Hendrik Schon and Zhenan Bao

But many researchers are working towards what is regarded as the ultimate in miniaturisation: to use clusters of molecules to form components rather than rely on the relatively bulky structures that form transistors on today's computer chips.

Each molecular transistor is 10 times smaller than any components created with today's most advanced chip making techniques.

The work by Bell Labs scientists Hendrik Schoen, Zhenan Bao and Hong Meng could have made this possible by creating tiny working circuits built from a class of organic materials known as thiols.

Commercial break

One of the main challenges of working on molecular scales is finding a way to build working devices. The trio have overcome this problem by making their clusters of carbon, hydrogen and sulphur molecules self assemble.

"We simply make a solution of the organic semiconductor, pour it on the base, and the molecules do the work of finding the electrodes and attaching themselves," said Dr Zhenan Bao.

Already the researchers have used the organic components to build a simple circuit, known as a voltage inverter, which is often used in computer processors. The research is reported in the journal Nature.

Bell Labs said it could be a decade before the tiny transistors started to appear in commercial devices.

At about the same time, current methods of making ever smaller components to fit on silicon chips are expected to hit fundamental physical limits.

In 1947, scientists William Shockley, John Bardeen and Walter Brattain invented the transistor at Bell Labs.