While the eye-opening video introducing 4-D Printing with general audiences (included above) has continued to spark interest for some months now, below is an selection from an interesting interview Scientific American had with 4-D Printing innovator Skylar Tibbits, director of the MIT Self-Assembly Lab:
When you talk about programmable materials containing information about the assembly process, what type of information are you talking about?
This information is in the form of a material’s properties, its shape (or geometry) and the amount of energy used to initiate self-assembly. One of our materials, for example, has properties that cause it to expand and change shape when you dip it in water. To maintain control over how the material changes, we designed it with a particular geometry that determines the direction it will curl, the number of times it will curl and the angles at which it will curl. Now we need to make the material more intuitive to use and easier to control.
How do you program these materials to behave in predictable ways?
You design them around the energy they need to self-assemble. You learn what thresholds of energy they will respond to and how they’ll react by testing a lot of them and then quantifying the results. We printed a 50-foot strand of our material and placed it in a pool for two reasons: to study how it would change when it was submerged and to determine whether we could work with really large structures. Part of the strand was made from a black, rigid plastic that determined its geometry—the angles and orientation as it changed. The strand was also made from a second strip of white plastic that expands 150 percent when placed in water. This reaction is what causes the strand to fold.
What are the biggest challenges facing 3-D printing, and how does 4-D printing address them?
Two of the problems with 3-D printing are the small bed size available in most printers and the difficulty of building things that require embedded electronics. We addressed the first by printing our 50-foot-long strand in the space of a five-inch cube. We tackled the second problem by using multifunctional materials designed to behave as though they have sensors and actuators so that you don’t have to add these electronics to the printed device.