In the deepest dreams of all of us, at least when it comes to science fiction, there are certainly the T1000 shapeshifters of Hollywood. However, a team of researchers has created a Terminator-type robot capable of melting in response to specific stimuli and then reassembling itself. Using alternating magnetic fields and taking inspiration from a particular sea creature, they created a first miniature prototype. Without forgetting, however, that the credit also goes to the materials specially used to construct the model.
What does the Terminator robot look like?
The properties of the model are due to the particular chemical composition of the alloy which constitutes it. The robot is in fact a mixture of ferromagnetic particles including Neodymium, Iron and Boron in a liquid metal matrix. With the particularity that the latter has a low melting point; in fact, the mixture is immersed in pure gallium.
The substance is made of what is called MPTM, or magnetoactive phase transitional matter. As its name suggests, it can pass from the solid phase to the liquid phase reversibly. Thanks to an alternating magnetic field, it heats up as it melts, then solidifies again at room temperature.
Diagram of the substance and its characteristics in relation to holoturia, top. Below, possible applications of the Terminator robot, including repairing electrical circuits.
MPTMs therefore uniquely combine high mechanical strength, high load capacity and high speed of locomotion. Their resistance reaches 21.2 MPa and their rigidity 1.98 GPa, for loads of up to 30 kg at more than 1.5 m/s, in solid phase. In the liquid phase, they exhibit excellent morphological adaptability (elongation, splitting, rupture, etc.).
Alloy characteristics and first results
The NdFeB microparticles are embedded in the gallium matrix with a clear phase separation between the NdFeB and the liquid metal. The mixing process is carried out mechanically so that an electronic scan can see the clear phase separation.
The researchers used pure gallium because its melting point (29.8°C) is close to room temperature. This obviously allows a rapid transition from solid to liquid phase under ambient conditions.
The solid gallium matrix also prevents the embedded NdFeB microparticles from moving or rotating. This therefore allows solid MPTMs to maintain a fixed and stable magnetic polarity. However, this freedom of movement limits the mobility in the liquid phase of the entire MPTM, while in the solid phase, with the application of certain magnetic field intensities, scientists recorded different speeds.
The researchers therefore carried out various tests in the solid and liquid phase, for example by making the material jump, pirouette and various movements. What made Terminator cry was the particular setup they ran one of the tests with. In fact, scientists modeled the substance in a figure similar to the Lego man placed behind the bars of a cage. However, when the alternating magnetic field is applied, the video clearly shows the figure melting and then reconstituting itself outside the bars.
The unsuspected creature that inspired it: the sea cucumber
At this point, after so much talk, one might expect that it was Hollywood that influenced the scientists at Carnegie Mellon and China University. But things are different than you might think; as in many studies of this type, nature, and in particular a sea creature, are at least partly responsible for what they achieved.
Sea cucumbers or sea cucumbers are the main source of inspiration for The MPTM; Also called sea cucumbers, these creatures have little to do with vegetables. These are actually animals that live on the seabed around the world, in the class of echinoderms. They have an elongated cylindrical appearance (reminiscent of cucumbers) with the anus and mouth located at opposite ends.
Oluturians in particular are characterized by so-called calcareous spicules, rigid all over their body, and use their mouths to feed by filtering water. Most of them are benthic, meaning they live permanently attached to the seabed and some are even sessile (attached to the substrate). Despite this, they can move in case of danger from scavengers and predators.
And so far, nothing very spectacular or distinctive, some might point out. But just mentioning one of their defense strategies draws comparisons to Hollywood and superhero movies. Indeed, sea cucumbers have great regenerative capacities: they can even eviscerate some of their organs. The watery lungs, long intestines, and single gonad are exploded to distract enemies and make it easier to escape, then they are able to regenerate everything in no time.
To add to its CV, this marine creature is of great importance to the marine ecosystem and biodiversity. Like their terrestrial cousins, in fact, like earthworms, they act as scavengers and are a deterrent. But that's not all: they also seem to help mitigate the acidifying effect of the oceans.
Applications of the Terminator robot
The sea cucumber is able to reversibly modify the stiffness of its tissues in order to improve its carrying capacity. Thanks to this feature, it can prevent physical damage caused by the environment. Just like researchers managed to do with the Terminator robot.
Okay, that's all well and good, some will say, but in practice what can it be used for, what have scientists thought about to use it profitably? Obviously not taking the first step towards what would be a real Terminator robot. Indeed, among other applications, researchers have also thought about the medical field and the possible contributions to the repair of devices that are difficult to access.
Liquid gallium
A first result was obtained by entrusting the MPTM with extraction and transport tasks. In a simulated stomach model, the team showed how the micromachine could transition to a liquid phase. This is in order to wrap around other foreign objects in the stomach itself and then become solid again. From there it is possible to extract the robot and its cargo.
In a similar test, the robot unloaded what it was carrying at predetermined points, again into the simulated stomach model. According to the authors, this is a demonstration of its potential as a drug delivery system.
Finally, a simulation showed how the liquid form of the robot could become a “universal screw”. By squeezing into hard-to-reach spaces and slipping into a screw socket, it could solidify. In short, the potential is there, but don't expect a terminator robot like Hollywood's T1000!