There are engineers at the University of Hong Kong in China who have designed tiny robots that are able to rapidly shift between liquid and solid states. These robots could remove objects from the human body or go in and fix electronics.

Inspired by Sea Cucumbers

The shapeshifting robots are inspired by sea cucumbers and engineers at the University of Hong Kong made them to rapidly reverse from liquid to solid states. They are also able to be magnetic and conduct electricity. The researchers put them through an obstacle course of varying tests to show their abilities, according to the journal, Matter.

Most robots have a hard body and fixed dimensions. These robots, also known as "soft" robots are flexible, but weak and their movements are hard to control. The softness of the robots is what gives them the ability to switch between liquid and solid states, along with having more functionality - according to Chengfeng Pan, leader of the engineering project for these robots.

A new material, called a phase-shifting material, was created and named "Magnetoactive solid-liquid phase transitional matter". The phase-shifting is done by embedding magnetic particles in gallium, a metal with a low melting point.

"The magnetic particles here have two roles," explains Carmel Majidi, mechanical engineer and senior author. "One is that they make the material responsive to an alternating magnetic field, so you can, through induction, heat up the material and cause the phase change. But the magnetic particles also give the robots mobility and the ability to move in response to the magnetic field."

Existing phase-shifting materials rely on heat guns, electrical currents, or other external heat sources to induce solid-to-liquid transformation. This new material has an extremely fluid liquid phase, compared to previous materials whose "liquid" phases are considerably more viscous.

Testing the Robots

The researchers tested their material's flexibility and strength in a variety of contexts. Using a magnetic field, the robots crossed obstacles, climbed up walls and even split in half to cooperatively move other objects around before coalescing back together. In one video, a robot shaped like a Lego man liquifies to ooze through a grid, after which it remolds back into its original shape.

If you recall the movie, Terminator 2, you will see the obvious resemblance with its main antagonist – the T-1000, a shape-shifting assassin robot that uses liquid metal to morph and disguise itself or create deadly weapons. In one pivotal scene, it enters a mental hospital by walking through prison bars.

While the kind of technology depicted in that movie is likely many decades or even centuries away, phase-shifting materials like that developed in this study could have many practical (and non-lethal) applications in the nearer term.

On the biomedical side, for example, the team used one of their robots to remove a foreign object from a model stomach, and to deliver drugs on-demand into the same stomach.

They also demonstrated how the material could work as "smart soldering" robots for wireless circuit assembly and repair (by oozing into hard-to-reach circuits and acting as both solder and conductor) and as a "universal" mechanical screw for assembling parts in hard-to-reach spaces (by melting into the threaded screw socket and then solidifying; no actual screwing required).

"We're pushing this material system in more practical ways to solve some very specific medical and engineering problems," said Pan.

"Future work should further explore how these robots could be used in a biomedical context," says Majidi. "What we're showing are just one-off demonstrations, proofs of concept, but much more study will be required to delve into how this could actually be used for drug delivery or for removing foreign objects."

What do you think of these phase-shifting robots - will they make the Terminator 2 some day?