How Printable Computers Will Work

Few argue that the next generation of computers will be nearly invisible, meaning that they will blend in with everyday objects. Flexible ink-like circuitry will be printed onto plastic or sprayed onto various other substrates, such as clothes. One of the scientists leading this printable computer revolution is Joseph Jacobson of MIT Media Lab's Nano Media Group. Jacobson has said that his group will be able to produce a simple printed microprocessor in late 2001 or early 2002. He also foresees being able to eventually produce a printed chip that could rival an Intel Pentium processor.

Jacobson's group has already succeeded in using an ordinary Hitachi ink jet printer to make several components for a printable computer. Using a nanoparticle-based ink made from suspending nano-size semiconductor particles in a liquid, researchers spray the components onto a plastic substrate. Here's a look at some of the printed components the MIT group has made with this process:

­ The Media Lab also created transistors using a different process. For that, polymer stamps are used with the architecture of the transistors in a positive relief. The stamp is then dipped in the nanoparticle ink and transferred to a substrate by hand. The next step will be to use an ink jet printer or some other kind of desktop fabricator to create printable transistors.

MIT isn't the only group developing ways to print computer circuitry. Plastic Logic, a company that sprang out of work begun at Cambridge University in England, plans to market the first plastic chip. The company has developed and patented a method of printing plastic onto polymer substrates, making cheap and flexible plastic transistors. The process is similar to the ink jet process used by MIT, but Plastic Logic adds carbon-based chemicals to alter the properties of the plastic. By printing the chips onto rolls of film, they can be applied to a variety of surfaces.

At Lucent Technologies' research company, Bell Labs Innovations, researchers developed the world's first printed transistor in 1997. Using plastic sheets similar to overhead projector transparencies, a liquid plastic semiconductor is applied over a stainless-steel mesh with a squeegee to form the multiple layers of the transistor. After the solvent of the mixture evaporates, the plastic remains. The process is very similar to how silk screening works. Lucent has teamed up with E Ink, an MIT offspring, to create printable displays. See How Electronic Ink Will Work for more information.

Soon, scientists will be able to create just about every part of a computer's hardware using a desktop fabricator. Plastic will take the place of silicon for many purposes, but don't expect to write off silicon as a valuable computer component for at least a decade or two. In the next section, we'll see how plastic stacks up against silicon and why we can expect silicon to stick around for many more years.

Plastic may revolutionize the semiconductor industry, but it won't be an overnight revolution. The sophistication of printable computers is still very simple. Currently, plastic fabrication devices can only produce transistors at the 25 micrometer scale (a micrometer is one-millionth of a meter); that's far from the .2 micrometer resolution that is needed to create a working microprocessor. Intel is able to crowd about 10 million transistors only a few hundred nanometers big onto one silicon chip. A nanometer is one-billionth of a meter.

Most researchers will tell you that printable computer components are not designed to replace silicon. Initially, we will see these printable devices used to give intelligence to everyday objects. They will be integrated into clothes, food labels and toys. One of the most exciting applications for printable electronics is creating a wallpaper that doubles as a television screen or computer monitor. MIT also plans to build a digital camera into a a business card.

Plastic does offer some benefits over silicon. Silicon is rigid, while plastic chips are flexible, allowing it to be placed on a variety of substrates. The problem is that, despite great hopes to create a plastic Pentium, printed inorganic transistors are still about 100 times slower than conventional transistors found on silicon chips.

Basically, printable computers represent the merging of conventional printing technologies with computer chip fabrication to produce cheaper, more flexible components. While many obstacles remain in its development, early products are ready to enter the market, such as disposable cell phones and computerized clothing. The next decade may bring us the ability to print out our own electronic devices and sophisticated computers.