A mini-robot for use in the human body must be externally controllable. In addition, a variable shape is of great advantage, so that the device can also squeeze through small openings. Mucus sticks together firmly and is extremely malleable at the same time: Chinese scientists gave it a flexible shell, ready for a tour of the digestive system.
The mucus consists of borax and polyvinyl alcohol
Interventions in the human body are usually accompanied by injuries. While many surgeries today are minimally invasive, it’s even better not to make an incision at all. Perhaps, the scientists at the University of Hong Kong thought, we could send a small robot to perform certain repairs in the body. From this idea was born the slime robot, which is made of a material with a lower density than water. The substances are called polyvinyl alcohol and borax, both of which are toxic to humans but do not come into direct contact with the body. The mucus is covered with a thin layer of silicone, which is not permanent, but is prepared for a short excursion into the body.
The robot is resilient and can heal itself
The supplied neodymium magnets allow control, the robot does not have its own drive. The researchers generate an external magnetic field and use it to maneuver their tiny device wherever they want. The slime robot is there to find and collect swallowed objects that are stuck in the digestive system. But he can also repair small objects or electrical leads from implants. It is about the size of a ping pong ball; it can therefore not be used in the arteries and veins. But it can also make itself very narrow, like a pen. In use, the device is very resilient – and it has the ability to heal itself. The scientists took the slime apart and put it back together, after which the robot was able to function normally again. 
The results of this research work have been published in the journal Advanced Functional Materials.