Two technologies at the edges of manufacturing are on the verge of coming together: self-assembly and 3D printing. In a recent talk given at the 2013 TED conference, Skylar Tibbits, an MIT faculty member in architecture, demonstrated a new material and process that results in a 3D-printed object self-assembling underwater.
The new technology is a combination of Tibbits' process with Stratasys' materials and its Objet Connex 500 Multi Materials inkjet 3D printer, Daniel Dikovsky, digital materials team leader for Stratasys, told Design News. The idea for the material came when Dikovsky and Tibbits discussed Tibbits' self-assembly projects, which he had been activating via mechanical energy.
The material is a combination of two acrylic polymers, one water expandable and one an existing, static Vero black already used with the Connex 500 multi-material printer. "The combined material acts as a source of energy when placed in water, but it also serves as an actuator," Dikovsky told us. "When exposed to water, it absorbs water, expands, and changes its dimensions."
When exposed separately to water, the water-expandable material only expands and does not change its form, and the static material does not change at all. When they're combined, the geometry of the 3D printed shape can be programmed to change form in predictable ways. You can watch a video here showing a cube shape self-assembling in water from a strand of the new combined material.
The key is in how they are programmed and combined at the particle level, which in the Objet Connex 500 is a very small 80-picoliter (80-nanogram) drop. These printers 3D print multiple materials, each a custom blend created from two out of several possible base materials. They are combined during printing from two separate cartridges. The mix is determined by a jetting pattern based on a software algorithm that integrates them in specific, programmed mixes to achieve certain thermal and mechanical properties.
Different combinations can be placed in different parts of the 3D model to provide varying degrees of hardness, flexibility, or thermal resistance.
In the MIT/Stratasys project, Tibbits used Autodesk Cyborg, and Objet used VoxCad simulation tools to predict the behavior of multi-material structures, including where to use the expanding material. VoxCad predicts the behavior of small structures, the links programmed to bend when exposed to water, and Cyborg predicts the behavior of the overall structure formed of those links, said Dikovsky.
Tibbits is the director of MIT's new Self-Assembly Lab, which will develop the new technology jointly with Stratasys. Although the video of Tibbits' 2013 TED Talk was not online at press time, the video of a 2011 TED Talk Tibbits gave on self-assembly of furniture and buildings can be found here. In this video, he says MIT researchers have worked on a MacroBot and a DeciBot, which are large-scale, 8-ft- and 12-ft-long reconfigurable robots made of mechanical and electronic components.