MIT Technology Review

Wednesday, January 11, 2012

The Art of 3-D Printing

MIT professor Neri Oxman is developing new design techniques that take advantage of "additive manufacturing."

As part of our special report on manufacturing, we asked Neri Oxman, a professor at the MIT Media Lab and an internationally recognized artist whose work is part of the permanent collection at the Museum of Modern Art in New York, to create a sculpture that would illustrate the future of manufacturing. (See a gallery of images here.)

What she produced, in collaboration with MIT materials science professor Craig Carter, is a powerful demonstration of the possibilities of 3-D printing, using techniques that take advantage of the capabilities of 3-D printers in ways that conventional manufacturing techniques cannot.  

3-D printing encompasses a range of technologies—from inkjet heads mounted on gantries that can deposit plastics layer by layer to form intricate models, to more recent laser-based systems that sinter metal powders to make durable parts for airplanes. 3-D printers have mainly been used for prototyping, but they are becoming an option for manufacturing as well, and may eventually even be used to print buildings, Oxman says. But designers and architects haven't yet learned to take advantage of their capabilities.

Oxman, who trained as an architect, says buildings are designed today with an eye toward the components they can be made of—sheets of plywood, panes of glass, steel beams, and concrete columns. As a result, those designs are limited, in much the way Lego bricks constrain the shapes that children can build. There are similar limitations in conventional manufacturing; there are some shapes that simply can't be built with existing molds and machining tools, and designers have had to design with these limits in mind.

Oxman is exploring ways to break with conventional design thinking by looking to patterns and processes found in nature, and using equations that define these processes to generate new designs. The results are often surprising shapes and structures that can be made only with 3-D printers.

To help develop the algorithms needed, Oxman has teamed up with Carter. In some cases, the algorithms provide new aesthetics, but they can also have practical applications—such as varying the structure to help bear loads. For one sculpture—a model of a chaise longue reclined chair—the team combined algorithms taken from nature with a map of the pressure a body exerts on a chair. The result depends on where the algorithms determine the chair needs to be soft to provide comfort and where it needs to be stiff to provide support.

For the sculpture Oxman made for Technology Review, she and Carter didn't have the same structural constraints imposed by a chair. The only requirements were that the result look like a cube, and that it should have the words "Making the Future" on one side. The resulting cube isn't a practical object, but it illustrates their approach to design.

The algorithms that define the shape of the sculpture are based on natural processes. One is the unmixing of two fluids. At high temperatures, oil and vinegar, for example, become completely soluble, but as the solution cools, the two fluids start to separate.

"You write down a set of equations based on what you know about thermodynamics and the kinetics of materials, and the equations develop these structures that look like fluids separating," Carter says. The resulting sculpture looks as if that process has been frozen and a cube has been cut from the center of the liquids. To make the lettering, Carter introduced other equations that caused one "fluid" to be attracted to the letters, and the other to be repelled. (To see an animation of how the fluids move to create the lettering, created by Carter, click here.)

Oxman and Carter fiddled with the algorithms until they reached the final shape they wanted, then shipped the resulting computer-aided design file to the 3-D printing company Objet to make the six-inch cube.

The technology used to make the cube involves an inkjet printer to lay down a layer of polymer ink, which is exposed to ultraviolet light to cure it. This requires printing a sacrificial support structure made of a soft polymer that can be blasted away with a jet of water.

Oxman's designs even push the limits of existing 3-D printers—the cube was so complex that it proved impossible to remove all of the supporting material from its center. Yet pushing the limits of 3-D printing is partly her goal. Indeed, her lab at MIT is developing new kinds of 3-D printers.

Oxman's lab is also developing robotic systems that could print large concrete structures for buildings. The new robotic system is being designed to be able to vary the density of the concrete, making it possible to use dense, strong concrete where it's needed for support, and lightweight, porous concrete for non-load bearing walls, to save on materials costs. Eventually, it may even be possible to print concrete that's so porous that it's translucent, reducing the need for indoor lighting.

Oxman continues to push forward designs with her art. She says the approach used for the Technology Review cube could serve as the basis for one of the 18 sculptures in a new exhibit she is developing for the Centre Pompidou in Paris. The exhibit will open this spring.