This SciFi looking robot cube was fitted with a 3-D printed skin which absorbs most of the energy the robot would have usually transferred to the ground. Credit: MIT

A team from MIT made headlines after it showed it’s possible to use a 3-D printer to make programmable materials of various stiffness on the fly. The printer was capable of layering different types of materials together, like liquids and solids, so the resulting material is tailored with laser precision to meet certain needs.

For instance, robots can be made sturdier, as well as delivery drones which Amazon and Google are currently experimenting with. However, everything from shoes to helmets to car bumpers can be made using this technique freeing independent producers from having to rely on suppliers’ standard items that sometimes can be too soft or too stiff — but never exactly like we want them.

Genuine custom work

Rubber and plastic are the most used damper materials. These are commonly known as “viscoelastics” due to their properties which share qualities of both liquids and solids.

There are many perks to viscoelastic materials. They’re cheap, compact and readily available but commercially available options come in fixed shapes, sizes, and material properties. Since 3-D printing has become mainstream, we can now easily create almost any object we want, even those with complicated geometries. The material properties have been harder to customize, though — not as easily as drawing and extruding objects in a software, at least.

“It’s hard to customize soft objects using existing fabrication methods, since you need to do injection moulding or some other industrial process,” says Jeffrey Lipton, a post-doc at MIT’s Computer Science and Artificial Intelligence Laboratory(CSAIL). “3-D printing opens up more possibilities and lets us ask the question, ‘can we make things we couldn’t make before?”

The team led by CSAIL Director Daniela Rus used a standard 3D extrusion printer. However, they used a special material called TangoBlack+, which emulates rubber’s solid/liquid properties. Also important was the special technique developed at MIT which is related to previous work involving the ejection of droplets of different material layer-by-layer and then using UV light to solidify the non-liquids.

The robot’s ‘skin’ uses only 1/250 the amount of energy it transfers to the ground.

To demonstrate their work, Rus and colleagues designed and assembled a cube-shaped robot with a rigid body, which was enveloped in a ‘soft skin’ 3-D printed with the new technique. Power by batteries, the tiny bot uses four layers of looped metal strip, serving as a spring to propel the contraption.

With the help of the 3-D printed skin, the bot landed four times more precisely, prompting the researchers to suggest such a shock-absorber might become very useful for the future’s home delivery drones.

“That reduction makes all the difference for preventing a rotor from breaking off of a drone or a sensor from cracking when it hits the floor,” says Rus, who oversaw the project and co-wrote a related paper. “These materials allow us to 3-D print robots with visco-elastic properties that can be inputted by the user at print-time as part of the fabrication process.”

“Being able to program different regions of an object has important implications for things like helmets,” says Robert MacCurdy, another post-doc from Rus’ lab. “You could have certain parts made of materials that are comfortable for your head to rest on, and other shock-absorbing materials for the sections that are most likely to be impacted in a collision.”

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