Robot engineers at the Iowa State University have developed robotic tentacles that are so soft and accurate that they can easily pick up an insect as delicate as an ant without crushing its body.

Iowa State researchers Jaeyoun Kim, Inho Cho and Jungwook Paek have discovered a way to give robots the ability to grab small objects without damaging them.

Their robot designs feature soft and elastic tentacles inspired by various animal appendages and body forms, such as those seen in the starfish, worm and octopus. The tentacles are made of rubber and plastic materials that are both soft and elastic.

Earlier soft robots make use of compressed air that is forced in and out of their arms in order to make them move. This process basically inflates and deflates the small pneumatic channels located in the robot's limbs similar to a balloon. Miniaturizing the robotic limbs, however, has been a difficult challenge for scientists.

Kim and his colleagues were able to solve this problem by designing their soft robots to grip and squeeze objects through a spiraling technique instead of simply grabbing them just like in previous robot schematics. The method can be compared to how the elephant uses its trunk to lift objects or how the octopus grabs its prey with tentacles.

Each one of the soft robots' tubes measure about five to eight millimeters in length. These tubes have walls that are eight to 32 microns thick and hollow channels that are 100 to 125 microns wide. The average width of a person's hair, in comparison, measures around 100 microns.

The researchers were able to create the microscopic tubes by dipping thin optical fibers in liquid silicone rubber solution. They then removed the hollow pipes from the rods after the fluid solidified. The tubes were inflated and deflated through pumps made of syringes.

By allowing gravity to pull on the silicone rubber inside the tubes as they solidified, the researchers were able to make one side of the tubes thicker compared to the other. As compressed air is forced into the tubes, the thinner sides are able to curl more than the thicker sides, causing the tubes to coil.

To allow the tubes to coil and uncoil every time they are inflated and deflated, Kim and his colleagues added silicone rubber rings to the exterior of the tubes.

In a recent interview, Kim explained that this was done to turn the single-turn coiling ability of the tubes into a multi-turn spiraling action.

The robot was able to grab and hold an ant that measured around 400 microns wide around its waist without crushing the insect. It used a gripping force of about 0.78 micronewtons.

The researchers believe this new technology can be used for medical purposes, such as safely manipulating blood vessels of patients through less invasive surgeries.

The Iowa State University study is featured in the Scientific Reports journal.

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