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Tuesday, February 26, 2013

Next, 4-D Printers

Now that the promise of 3-D printing has landed on the national agenda, researchers want to increase the stakes â€" with so-called 4-D printing.

No, the printers won’t generate hypercubes. Rather, the scientists claim that their “fourth dimension” refers to time â€" as in the space-time continuum described by the mathematician Hermann Minkowski early in the 20th century. The 4-D structures are first generated by 3-D printers but then transform when activated.

“This is a whole new idea of printing, where you don’t just print static objects; you print things that turn into other things,” explained Skylar Tibbits, an M.I.T. researcher who is working on the printer collaboraton with Stratasys, an Israeli 3-D printing company. Mr. Tibbits’s research has focused on self-assembly technologies, for things ranging from toys to furniture.

The research, which was announced Tuesday at the TED Conference in Long Beach, Calif., is into what essentially resembles self-folding origami.

The structures need external activation energy to transform. Currently the early prototypes developed by Mr. Tibbits and Stratsys use water to provide that energy. The self-folding structures are first printed out as long strands made of two core materials in combination â€" a synthetic polymer that can expand to more than twice its volume in water, and another polymer that is rigid in water. By carefully combining the two materials using specific blueprints, the expansion of the water-absorbing substa! nce drives the joints to move, creating a predetermined geometrical transformation.

Mr. Tibbits currently has created two working prototypes: one that slowly snaps into the letters “M.I.T.” and another that changes into a simple cube. The speed of transformation depends on the temperature and buoyancy of the water, as well as the exact makeup of water-absorbing material.

Mr. Tibbits has been trying to create more complex and dense shapes, with limited success. “The big thing we are up against is tangling,” Mr. Tibbits said. As a result, Mr. Tibbits is trying to make precise predictions about the sequence of how the structures fold together. In many ways, the folding processes resemble basic protein formation, Mr. Tibbits noted.

Stratasys’s director of global education, Shelly Linor, says Mr. Tibbets’s research shows the potential of programmable materials in the future of manufacturing.

It lso opens up the concept of “environmental manufacturing,” in which companies can take advantage of the ambient sources of surrounding energy. Aside from water, structures could also be activated by light, heat, current or even sound, Mr. Tibbets said.

Right now the transformations happen in only one direction. Mr. Tibbets said a future step in his research would be to see if they could be reversed. If so, the systems could become self-sustaining in environments with cyclical change. For example, instead of using pumps, pipes could expand and contract, in a process resembling peristalsis, to push water.