3-D printing is a technology that is on everyone’s lips at the moment. From consumer products to human organs, the applications of 3-D printing could change the way we manufacture. However, Skylar Tibbits of MIT is preparing to take this further. In his lab, scientists are working on introducing a fourth dimension to 3-D printing: time. What if 3-D printed objects “could change over time”? This idea has been called self-assembly, or ‘4-D printing’.
Before we proceed, it is important to understand what self-assembly actually is. Tibbits defines self-assembly as “a process by which disordered parts build into an ordered structure through simple interactions with each other”. To see an example, click on this link: http://video.mit.edu/watch/4d-printing-mit-self-folding-strand-13803/.
Parts can assemble themselves as they contain intelligence. In other words, matter has been programmed. By collaborating with the firm Stratasys, Tibbits uses their “Objet Connex multi-material 3-D printing technology” to program specific properties into the particles being printed. When exposed to water or heat, the particles gain the necessary activation energy to self-assemble into different shapes. Tibbits explains that the 4-D printed components can be placed inside a container. Next, the container can be shaken to provide heat (activation energy) and the components will self-assemble into the pre-designed geometry. The best part about this is: no manual assembly is required! The whole assembly is automated.
The applications of this technology might allow 3-D printing to realize its full potential. Once again, this idea is best illustrated through example. For one, smart materials could be used in piping. Suppose that over time, a pipe changes changes its shape from perfectly cylindrical to the third shape shown below. Instead of using power to propel water, the 4-D printed pipe could “undulate to move the water”. This is similar to peristalsis, the “wave of muscle contractions that moves food through our digestive tract”. Next, the pipe could expand into the fourth shape to allow more water to flow. Alternatively, the pipe could close itself completely to stop water flow. Another application that has been suggested is using 4-D printing in certain parts of building construction. The smart material could adapt itself during earthquakes and natural disasters to keep the structure stable and its hosts safe.
4-D printing has potential for the future, but it also faces a few trade offs. Firstly, the printing process is relatively slow compared to other methods. Printing large objects can take days. Secondly, there is a limitation with respect to the materials that can be used. Moreover, the materials currently available are nowhere as strong or effective as those used in modern processes. Thirdly, 4-D printing faces a limitation in size. For example, one cannot print an entire building. Tibbits likes to give the following example to convey this idea: “to 3-D-print a skyscraper, you would first have to build a skyscraper-sized printer”.
But this is where the beauty of 4-D printing comes to the fore. Instead of printing a massive object at one go, individual parts can be printed. Next, self-assembly can be used to synthesize the entire object from its individual parts. This idea is simple but its applications are powerful. “People are really excited about it, but I think we have barely scratched the surface,” says Skylar Tibbits. In the future, imagine parts self-assembling into a skyscraper right before your eyes. This Inception-like scenario provides a glimpse into the possible future of 4-D printing.
TED talk by Skylar Tibbits: