16 September 2022

Instant Robot

Chinese scientists have developed a biodegradable "millirobot"

Tatiana Matveeva, "Scientific Russia"

Researchers from the City University of Hong Kong (China) have designed a soft robot that can roll, climb and grab -- and then easily dissolves after doing its job. The robot, which can be used in biomedicine, is powered by a magnetic field, transmits EurekAlert!. The development is described in the journal ACS Applied Polymer Materials (Yang et al., Soft Tunable Gelatin Robot with Insect-like Claw for Grasping, Transportation, and Delivery). 

Soft "millirobots" are a promising innovation in biomedicine. Their unique structure allows them, for example, to roll over uneven tissues of the gastrointestinal tract. Someday they can even be covered with a solution of the drug and deliver the drug directly to the focus of inflammation. However, most millirobots are made of non-degradable materials such as silicone, which means they can only be removed surgically if they are used for clinical purposes. In addition, these materials are not very flexible and do not allow you to fine-tune the properties of the robot.

The new millirobot is based on a gelatin solution mixed with iron oxide microparticles. The material was placed over a permanent magnet, which caused the microparticles in the solution to push the gel out, forming insect-like "legs" along the magnetic field lines. Then the hydrogel was placed in the cold to harden it. At the last stage, the material was soaked in ammonium sulfate to cause the formation of cross-links in the hydrogel. This made it even stronger. Changing various factors, such as the composition of the ammonium sulfate solution, the thickness of the gel or the strength of the magnetic field, allowed the researchers to adjust the properties of the robot. For example, the farther away the magnet was from the hydrogel, the longer the "legs" of the millibot became and the smaller their number was. 

Since iron oxide microparticles form magnetic chains inside the gel, moving the magnet next to the hydrogel caused the "legs" to bend and try to grab onto the object. In the experiments, the robot captured a cylinder and a rubber band printed on a 3D printer and moved each of them to new places. In addition, the researchers tested the millirobot's ability to deliver medicine by coating it with a dye solution and then scrolling through a stomach model. Once at the destination, the robot turned around and released the paint using magnets. Because it is made using water-soluble gelatin, the millirobot easily decomposes in water in two days, leaving behind only tiny magnetic particles.

A video about the work of the millirobot and its manufacture can be viewed here.

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