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Last Updated: Monday, 20 March 2006, 13:37 GMT
Chemists work on plastic promise
By Jonathan Fildes
BBC News science and technology reporter

Semi-conducting polythiophene as ink (Merck)
The team has already used the polymer to print transistors
A new plastic that could rival silicon as the material of choice for some electronic devices has been developed.

The invention could eventually slash the cost of flat panel screens and bring electronic paper into common use.

The new material can also be laid down using simple printing techniques rather than the expensive and elaborate methods used to process silicon.

The plastic, reported in the journal Nature Materials, is the work of a US-UK industrial and academic team.

The researchers told the journal that until now, the speed at which polymers conduct electricity has been too slow for them to fully challenge silicon-based materials.

However, the team claims, this barrier can now be overcome using some clever chemistry.

Chemical tweaks

The new material is an organic polymer, a class of substances that are used to make everything from bin bags to solar panels. They are also used in some electronic devices already.

In 2004, electronics giant Philips announced production of a flexible display using organic polymers, while other companies such as Cambridge Display Technology use them to manufacture organic light-emitting diodes (LEDs).

However, the performance of the plastics has always made them second choice for more mainstream applications. The new semi-conducting polythiophene could change all that.

It has been tweaked by chemists to alter its molecular structure, meaning it is more efficient at carrying an electrical current and can also be dissolved in a solution to produce an ink.

These modifications give the material its edge over traditional silicon which must be processed at high temperatures and in vacuums. This is not only slow and expensive but produces a large amount of waste.

Instead, the new polymer can be printed using traditional inkjet printers or techniques similar to those used to produce magazines and wallpaper.

This means it can easily be printed on large flexible surfaces, making it attractive for use in electronic paper where rigid silicon cannot be used.

Specific jobs

The team has already used the technique to print transistors, a key building block of electronic circuits.

The working devices are six times faster than any polymer transistors previously reported, and are similar in performance to the silicon used in flat panel screens.

The team behind the discovery believes the material will be used in areas where silicon struggles to compete.

"Initial applications might be in simple, disposable electronic items, followed by small reflective displays for PDAs or e-paper," said Iain McCulloch, a senior project manager at UK-based Merck Chemicals and one of the authors of the paper.

"Further away are large, high-resolution displays," he told the BBC News website.

However, it is unlikely that the material will ever rival silicon in the manufacture of high-speed computer chips.

The core of all modern computers, these require ultra-pure materials and precision design that is simply not achievable with these polymers.

"We are still orders of magnitude away," Iain McCulloch admits.

The research team incorporated members from Merck Chemicals in Southampton, UK; Palo Alto Research Center, California; Department of Materials Science and Engineering, Stanford University; and the Stanford Synchrotron Radiation Laboratory.

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