You probably wished, at least once, that you could reach into your computer monitor and pull out a piece of pizza. Although you can't do so today, it may be possible to print edible objects in the near future, according to Adrian Bowyer of the Biometrics Research Group at the University of Bath. He's the founder of the RepRap project (short for Replicating Rapid-prototyper), which is based on a 3-D printer capable of replicating three-dimensional objects and recreating 60 percent of itself.

John von Neumann had spent time debating theories about self-reproducing machines during the 1950s, Bowyer discovered. Neumann called these machines Universal Constructors, and they inspired Bowyer to create a self-replicating 3-D printer. However, the idea to produce rapid prototyping printing products emerged in the late 1980s, Bowyer says. Initially, three-dimensional printing was used to create models and model parts, and sculptors used the technology to create intricate shapes for art exhibitions.

However, Bowyer believes that he's the first person to suggest a Universal Constructor (a machine that can self-replicate) that can also create other parts. In 2001, Bowyer convinced Bath University to invest in 3-D printing, and the university purchased two machines. By 2004, Bowyer realized that it might be possible to create a 3-D printer that could generally recreate itself, except for items such as electric motors and logic chips. The created parts have to be assembled by hand.

"Not counting nuts and bolts, RepRap can make 60 percent of its parts," says Bowyer. "The other parts are designed to be cheaply available everywhere." As he explains, the objects produced by RepRap are similar to Legos in both strength and durability. Most are made from thermoplastic polymer, with some containing ceramic slurries and silicon nitride. Materials such as silicone, wood and metal may also potentially be used, he says.

The RepRap is about the size of a standard photocopier. A user decides which model to print (or creates his own model). Next, the computer communicates with the RepRap as it would with a 2-D printer. The RepRap printer fills up with white powder surrounding the solid plastic object that it's creating, referencing the image displayed on the computer screen. Layer by layer, the object is created from the bottom up.

Among the items created so far are a pair of shoes, an iPod bracket, and even a martini glass. The RepRap should be able to create all its mechanical components on its own in the near future, says Bowyer, although some parts (like sensors or cameras) would have to be added.