This may be the ugliest robot you've ever seen, but it can deform at will like venom, be cut off and be reborn.

There is an alien life form that can be parasitic on humans and gives the host a powerful ability to deform and stretch at will like a fluid and enter a narrow space to carry out acts of destruction. It is venom.

Although this creature is fictional, a group of scientists at the Chinese University of Hong Kong, inspired by venom, have created a Slim robot, which also has amazing deformability and can travel freely in a cramped space. for special tasks. The difference is that the task set by the researchers is not destruction, but more salvation.

Although the robot is not pleasing in appearance and even has a stool temperament, under the control of humans, it can "swallow" tiny objects with its body; it can also wrap copper wire tightly with smooth movement and even repair disconnected circuits.

Scientists hope that such a flexible robot can enter the human body to provide services in the future, but what kind of service is it?

? Slim has the magic of transformation.

Slime, a sticky, slippery and elastic object, is very good at deformation and often shows amazing magic in fantasy works. Back to reality, Shrem took off the supernatural halo, but its sticky and elastic physical properties still exist, can bend and stretch, and the feel of the squeeze is pleasant, so it has become a human toy.

When making Slim, the simplest recipe is a combination of polyvinyl alcohol (PVA) and borax, plus water. Among them, PVA is often used to make thickeners: this polymer compound contains a large amount of hydroxyl (- OH), which will form many hydrogen bonds when it meets water, which helps to increase the viscosity. In general, the higher the degree of polymerization of PVA, the more likely its aqueous solution will become sticky.

If boric acid is added to the aqueous solution of PVA, it will exist in the form of borate ions. The ion has four hydroxyl radicals that can form hydrogen bonds with hydroxyl groups (- OH) in PVA, allowing PVA macromolecules to cross-link each other, helping to form a stable network structure and make a thicker and more elastic Slim.

If we hold Slim in our hands, we can easily change its shape and even make people wonder whether it is solid or liquid. In fact, this is a non-Newtonian fluid (non-newtonian fluid). Our common water and oil are Newtonian fluids, and the viscosity is constant, or the flow capacity is constant. The viscosity of non-Newtonian fluids is not constant, and Slim can become more like a liquid or a solid depending on the force. It also has another moving name in Chinese, called "ghost saliva".

Scientists at the Chinese University of Hong Kong used the same principle when developing venom robots. However, they added neodymium magnet (neodymium magnet) particles in addition to PVA and borax. In this way, a simple Slim becomes a controllable robot.

After the birth of a robot, scientists first have to test its metamorphosis skills. Of course, instead of pinching it, it exerts a specific magnetic field from the outside to make the Slim robot the desired shape. The team first tested in a simulator that circular ferromagnets can turn robots into circles, and more complex rings and hexagonal star shapes can all be achieved in the same way.

In reality, scientists place a small robot with a diameter of 9mm on a polymethyl methacrylate (PMMA) substrate with a permanent magnet 4mm below the substrate, running away from directly below the robot. As the permanent magnet runs farther and farther away, the robot's body gradually lengthens, from the 9mm diameter "ball" to a 60mm long "snake", about seven times the natural length.

Scientists say the excellent ability to deform allows the robot to stretch freely. At the same time, the friction force on the robot and the setting of the magnetic field also allow it to leave part of it in place, in every place it has passed. In this way, people can see with the naked eye how far it can stretch.

Since a robot can draw its own path, scientists will not just let it draw a simple straight line. They modified the trajectory of the permanent magnet so that the Slim robot finished writing the abbreviation "CUHK" of CUHK, and used the COMSOL Multiphysics software to restore Slim's stretching process.

What if the human swallowed the button battery by mistake?

The team hopes that the Slim robot can use its deformability to travel through a variety of impassable spaces to perform tasks that were previously difficult to accomplish.

As a result, they designed difficult motor tasks for the robot, starting with narrow passages. The diameter of the passageway in the swimming pool (unsealed up and down) starts at 6 mm and narrows to 4.5 mm, 3 mm, or even 1.5 mm. As a result, the robot successfully swam through the four channels under the guidance of a magnet, and although the 1.5mm channel took about 180 seconds to complete, the process was smooth in the eyes of scientists. But this is only the first task.

In the second task, the channel that the robot has to pass through becomes a pipe with a wall around it, and there is no longer liquid in the pipe, and the task path is no longer a straight line but a zigzag. Controlled by a magnet, a 1 ml robot (if converted into a cube, the edge is about 10 mm long) can easily pass through a circuitous pipe with a diameter of only 5 mm. The third task is more complicated. In addition to setting up the necessary channels, scientists have also added some useless channels to form a "maze", some of which are wide and some narrow. This time, the robot still cooperates with the magnet to reach the finish line.

In the fourth task, the Slim robot needs to pass on uneven roads, with high and low terrain, with a distance of about 6.28mm between the two adjacent highs and a vertical distance of 3mm between the highs and lows. As a result, this terrain is still not difficult to beat the Slim robot, which is good at transforming.

Through these tests, scientists are delighted with the adaptability of robots, which they believe can effectively reduce damage to the surrounding environment. This is mentioned because the team hopes that Magnetic Slim will one day be able to enter the human body to perform a task.

As for the task, the scientists sandwiched the button battery to the inner wall of the pig's large intestine, simulating the scene of human swallowing: 30 minutes later, the button battery caused significant damage to the intestinal wall. In that case, robots need to have the ability to grasp objects in order to have a chance to avoid such injuries.

So the team tested the ability of the Slim robot with a wrinkled simulated stomach model, and then found that it walked through a rugged road under a magnetic field, came to the button battery for dozens of seconds, and curled its body. Quickly wrap the button battery to prevent it from continuing to cause damage to the "human body".

Of course, before the robot really enters the human service, its own material can not cause harm to the human body in the first place. The neodymium magnet in Slim is toxic. In order to avoid its contact with the human body, scientists wrapped it with a relatively stable silica coating, but its safety needs to be further confirmed.

Cut off and can repair itself.

In addition, the Slim robot has another important skill, which is "self-healing".

The scientists dyed one piece of Slim blue and the other green. Then, cut the two slices into two pieces, and then line up the four little Slims, separated by blue and green. This is where the self-healing process begins. Soon, they re-integrated into a big Slim, and the color change is the joint.

To test whether the reconnected Slim is still tough, the scientists stretched it to 8.6 times its natural length, and the alternating blue and green positions did not break. In other words, after self-healing, Shrem maintained good plasticity, and the joint did not become very fragile. Note that Slim in this experiment did not add magnetic partic