In conventional construction, workers piece together buildings from mass-produced, prefabricated bricks, I-beams, concrete columns, plates of glass and so on. Neri Oxman, an architect and a professor at MIT’s Media Lab, intends to print them instead—essentially using concrete, polymers, and other materials in place of ink. Oxman is developing a new way of designing buildings to take advantage of the flexibility that printing can provide. If she’s successful, her approach could lead to designs that are impossible with today’s construction methods.
Existing 3-D printers, also called rapid prototyping machines, build structures layer by layer. So far these machines have been used mainly to make detailed plastic models based on computer designs. But as such printers improve and become capable of using more durable materials, including metals, they’ve become a potentially interesting way to make working products.
Oxman is working to extend the capabilities of these machines—making it possible to change the elasticity of a polymer or the porosity of concrete as it’s printed, for example—and mounting print heads on flexible robot arms that have greater freedom of movement than current printers.
She’s also drawing inspiration from nature to develop new design strategies that take advantage of these capabilities. For example, the density of wood in a palm tree trunk varies, depending on the load it must support. The densest wood is on the outside, where bending stress is the greatest, while the center is porous and weighs less. Oxman estimates that making concrete columns this way—with low-density porous concrete in the center—could reduce the amount of concrete needed by more than 10 percent, significant savings on the scale of a construction project.
Oxman is developing software to realize her design strategy. She inputs data about physical stresses on a structure, as well as design constraints such as size, overall shape, and the need to let light into certain areas of a building. Drawing on this information, the software applies algorithms to specify how the material properties need to change throughout a structure. Then she prints out small models based on these specifications.
The early results of her work are so beautiful and intriguing that they’ve been featured at the Museum of Modern Art in New York and the Museum of Science in Boston. One example, which she calls Beast, is a chair whose design is based on the shape of a human body (her own) and the predicted distribution of pressure on the chair. The resulting 3-D model features a complex network of cells and branching structures that are soft where needed to relieve pressure and stiff where needed for support.
The work is at an early stage, but the new approach to construction and design suggests many new possibilities. A load-bearing wall could be printed in elaborate patterns that correspond to the stresses it will experience from the load it supports from wind or earthquakes, for instance.