This 3D-printed robot walks on sand - but could superhero tech take it even further?

A new 3D-printed, four-legged soft robot is the first of its kind able to walk on rough surfaces.

The robot, developed by engineers at the University of California San Diego, was built using a high-end 3D printer that allowed the researchers to combine both soft and rigid materials within the same component.

The idea – borrowed from nature – allowed researchers to create more complex shapes for the robot’s legs. “In nature, complexity has a very low cost,” said Michael Tolley, a mechanical engineering professor at the university, and leader of the research group. “Using new manufacturing techniques like 3D printing, we’re trying to translate this to robotics.”

Soft robots are constructed from compliant materials, similar to living organisms. The legs of this robot are constructed from three actuators – parallels, connected sealed inflatable chambers, which are 3D-printed from a rubber-like material. These chambers are hollow on the inside, and so can be inflated and deflated in different ways to bend the legs.  

The four legs are connected to a rigid body, and its gait depends on the order, timing and pressure in which the pistons in the legs are inflated. Until now, soft robots have only been able to shuffle or crawl along without lifting their legs, but this robot was able to climb over obstacles and walk on different terrains. It was tested on large rocks, inclined surfaces and sand, and was able to transition from walking to crawling in a confined space.

The current model of the robot is tethered to a circuit board and air pump, but researchers are now working on miniaturising both those components so that it can walk independently.

However, Jonathan Rossiter, a professor of soft robotics and intelligent systems at the University of Bristol, told Professional Engineering that the soft robotics community is looking to move away from pumps and motors. “There’s a great potential here to develop new actuation and sensing technologies which don’t rely on these conventional hydraulics, pneumatics or electro-magnetic motors and solenoids and things like that,” he said.

His lab is working on electro active polymers, which change shape or rigidity when a current is applied to them - like Batman's wingsuit in the movie The Dark Knight. “In this robot, there’s a leg and a pipe, and it needs to have the air supply. But what happens if we just take a battery and you plug that into the leg. These electro-active polymers in the leg contract and bend and twist, and that’s much more like muscles. Our goal in the soft robotics community is to move more towards that end of things.”