Plastic makes chip printing possible

This might sound a bit mad, but imagine if you could print out your own computer. With new developments in fabricating semiconductor chips from plastic instead of silicon, it might just happen.

The conventional manufacturing process for silicon-based chips is expensive, slow and error-prone. A typical chip production plant costs upwards of $2 billion, and it takes two weeks of full-time manufacturing to make a single chip of Pentium-scale complexity.

It's like that because each 12in silicon wafer, which can hold a few hundred identical chips, must be processed again and again by different machines, as the complex patterns are etched into the silicon. But now a completely different manufacturing technique is emerging, which promises to revolutionise the industry. Researchers are printing chips onto flexible plastic sheets, and they're doing it on the desktop.

Thinking ink

Joseph Jacobson, director of the Printed PC Lab at Massachusetts Institute of Technology (MIT), is working on printing transistors using an 'ink' comprising nanometre-scale semiconducting particles www.media.mit.edu/nanomedia/projects.html. Amazingly, this is achieved using a conventional inkjet printer.

Another approach they're taking is to create a rubber stamp that holds a circuit layout in relief. The stamp is 'inked' with the semiconducting particles, and the circuit is stamped onto a plastic substrate.

In the UK, a new company called Plastic Logic has patented a method for depositing plastic onto a polymer substrate, using an inkjet-based printing system www.plasticlogic.com. It uses organic polymers that, if deposited suitably on the substrate, behave as thin-film transistors.

The company is specifically working to print the arrays of switching transistors needed by flatpanel liquid crystal displays, which currently use conventional silicon technology.

Plastic chips proliferate

Many industry watchers are cautious about some of the dramatic claims made by the chip printers. While unarguably cheaper and more efficient to produce, the transistors on plastic chips currently work far slower than those made from silicon, and their packing densities are several hundred times less.

But there are many applications, such as smartcards and intelligent food labelling, which don't need the massive processing power of conventional chips. And it's in examples of embedded computing like these that plastic chips are likely to proliferate.

Disposable mobile phone on test

Combinations of printed circuits and conventional chips are already appearing. New Jersey toy designer Randi Altschul is about to start test-marketing the world's first disposable mobile phone www.dtcproducts.com/home.html. According to her patent, the keys and circuit interconnections of the phone are printed onto a substrate, which also hosts a conventional phone microprocessor. The substrate is then folded over on itself, to make a multi-layered sandwich about half a centimetre thick. This is covered with a plastic wallet which forms the phone's body. A hands-free mic and earpiece plug in.

Altschul's initial model will only be able to make outgoing calls, and she predicts that it will sell for $10 (£6.25) from a vending machine. You'll get an hour's talk time, and if you don't want to top it up from your service provider, you just throw the phone away.

Altschul says her company has more ambitious plans, including disposable handheld games, and even laptops.

The idea of having a machine on your desktop that can print chips opens up some amazing possibilities. You could download a new CPU design from the web, print the chip out onto a bit of blank plastic substrate, and install it straight into your PC.

First we had open-source software, now it's open-source hardware. What will they think of next?