Octopus-arm-like tool may find use in surgery

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The octopus arm tool moves between water balloons, standing in for delicate organs(Credit: Tommaso Ranzani)

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When surgeons are trying to operate on hard-to-reach organs, they'll often have to make multiple incisions to get at the area from different angles, or use tools such as retractors to pull other tissue out of the way. A team of researchers from Italy's Sant'Anna School of Advanced Studies, however, is developing an alternative – a flexible octopus arm-inspired tool that can squirm its way between organs, then hold them back while simultaneously operating.

The prototype device consists of two joined modules, each one containing three cylindrical air chambers. By selectively varying the inflation of different combinations of those chambers, it's possible to get the arm to bend and stretch in different directions, anywhere along its length.

In order to be able to hold tissue out of the way, however, it can't be too flexible – at least, not all the time. That's why it also has a granular material (ground coffee, actually) contained within a flexible interior membrane. Ordinarily, that material is able to shift around easily, allowing the device to remain pliable.

Once a vacuum is applied and the air is sucked out of the membrane, though, the density of the material increases as the coffee grounds all jam together. It's a phenomenon appropriately known as "granular jamming," and it causes the membrane – and thus the device itself – to become rigid until the vacuum is released.

The idea is that the arm would first be in a flexible state, in order to move its business end to the target site without the need for retractors or other tools. Once it reached its target, it would push the surrounding tissue away from that area, then stiffen itself up to hold that position. Surgical tools on its end would then be remotely operated by a surgeon, to perform the procedure.

In tests of the prototype, it was able to bend at angles of up to 255 degrees, stretch up to 62 percent of its relaxed length, and stiffen by up to 200 percent. It was also able to manipulate water balloons – representing organs – without damaging them.

"Traditional surgical tasks often require the use of multiple specialized instruments such as graspers, retractors, vision systems and dissectors to carry out a single procedure," says lead scientist Dr. Tommaso Ranzani. "We believe our device is the first step to creating an instrument that is able to perform all of these tasks, as well as reach remote areas of the body and safely support organs around the target site."

A paper on the arm was recently published in the journal Bioinspiration and Biomimetics. The research is being carried out as part of the European STIFF-FLOP project.

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