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Researchers are working to someday create a robotic eel that could ultimately swim through the body to deliver drugs to cells or genes.

A team of researchers from Brandeis University has developed a model using chemicals and microscopic containers of a network of neurons that—once embedded in a gel—could actually behave much like how an eel swims through the ocean in a zigzagged manner. The “robotic eel” is part of a larger effort to build machines made from chemicals and other synthetic materials that behave like living organisms.

“We hope the material will behave in the same way an eel's body does in response to the firings of its neurons,” physicist Seth Fraden said in a statement. “It will slither away.”

An eel’s spine runs the length of its body, surround on both sides by a column of neurons that fire sequentially down one of the columns to cause a wave of muscular contraction to make the spine curve. When the neurons in the other column fire, the spine curves in the opposite direction to enable to animal to swim the way it does.

To duplicate this process, the researchers first had to create a neuron.Neurons oscillate between the excitatory state, where they cause other neurons to fire and inhibitory state, where they keep other neurons from firing. Fraden used BZ reactions——a class of reactions that result in the establishment of a nonlinear chemical oscillator—to create his artificial neurons.

The engineers then built a container similar to an ice cube tray to hold the neurons. The container basically formed columns comparable to the lines of neurons on either side of the eel’s backbone.

Each of the chambers was filled with a liquid solution that contains the chemicals necessary to facilitate a BZ reaction..

The first BZ reaction occurred in the container at the top of one of the columns and when it turned excitatory, it released a molecule that entered the container directly beneath it. The BZ reaction then turned inhibitory and released a molecule that traveled to the container directly across from it, putting the BZ reaction on hold.

When all the BZ reactions in the first columns were completed, the reactions in the second column started.

The second column’s reactions also proceeded one after the other and suppressed the reactions in the first column, which started up again after the second column’s reactions finished.

The BZ reactions were interconnected and communicated with one another in the same order as the eel’s spinal neurons, going off one at a time, one column after the other.  The researchers then knit the BZ reactions together so they would act as one single entity.

Fraden has selected a chemical-responsive shape-changing gel into which he will implant his ice cube tray apparatus. 

The study was published in Lab on a Chip.

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