October 26, 2021

I, Science

The science magazine of Imperial College

Margot Lesaffre investigates how our knowledge of the biology of the octopus arm is leading to innovations in surgery

octopus flickr joe parks 11847079564_8b85ecad02_k_1024wWith its frightening appearance and gargantuan size, this ocean-dwelling creature is so big that its head can be mistaken for an island, its mouth is capable of devouring who ought to fish in its territory, and its arms can reach as high as the top of a sailing ship’s main mast. Legends of the Kraken originate from the 13th century and are still present in today’s popular culture, but beliefs of this fearsome giant squid are about to change as a team of researchers in Italy have managed to tame the creature for our own benefit.

Dr Tommaso Ranzani and his team from Sant’Anna School of Advanced Studies have constructed a robotic arm designed for surgical operations. The octopus-inspired technology is able to bend, stretch and quickly switch between a flexible state and a rigid state, a first in the field of medical robotics.

The new robotic arm is less invasive than traditional laparoscopic surgery. “The possible complication with laparoscopic surgery is damaging another organ than the one you are trying to operate on,” says Frances Evans, a gynaecologist at North Middlesex hospital. The new robotic arm is able to access confined regions of the body by nudging organs out of the way with one part, while operating with the other. The new robotic arm also reduces the number of instruments needed, and thus the number of entry incisions necessary for surgical operations.

So, what’s all the fuss about an octopus’s arm? If you have ever struggled to open an oyster, imagine how hard it might be for a soft-bodied octopus. Octopuses lack a skeleton, yet its arms are able to stiffen to perform many tasks, including opening shellfish to feed from it. “I am amazed by the dexterity that they have and the fact that they totally lack any rigid structures,” says Dr Matteo Cianchetti, co-author of the study.

Granular jamming

After observations done on octopuses in their laboratory, the researchers at Sant’Anna identified the peculiar structure that allows octopuses to stiffen their arms when necessary. Ranzani and his team reproduced this mechanism by using ‘granular jamming’ in which a flexible membrane is filled with granules. When a vacuum is applied to the membrane, the density increases and the whole membrane becomes rigid. It’s exactly what happens with coffee bags. Coffee bags bought at the supermarket are rigid and stiff because there is no air inside the bag. If a cut is made in the bag, it fills with air and the coffee beans are then able to move inside the bag.

The new robotic device is also made of two identical modules. Each module contains several cylindrical chambers that can be inflated using gas. Alternating and combining the inflation of the chambers allows each module to bend and stretch in several directions.

In traditional surgery, to carry out a single procedure, a surgeon needs a range of specialized instruments such as graspers, retractors, vision systems and scalpels. The robotic arm is therefore a real advantage for the surgeon. “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,” Ranzani says.

However, Cianchetti insists that this device “will be complementary to the traditional robot.” He adds that the key is to “combine these two approaches to have an optimal way of performing an operation.”

The results of this new study are promising, but Evans is more sceptical about the new robotic arm. “At the moment, all instruments are rigid, but the fact that the new instrument is more flexible does not give the surgeon any better tactile sense or a three-dimensional perception compared to rigid instruments.”

“At the moment, we are at a very early stage in the project,” Cianchetti says.

The team is thus far from thinking about clinical trials. The ability of the robotic arm to manipulate organs, while surgical tasks are performed, was only demonstrated in simulated scenarios where organs were represented by water-filled balloons. But the research remains a big step in the field of medical robotics. “This particular group of researchers are addressing a very complex problem in medical robotics that a lot of other groups, including ourselves, [have been] trying to address for many years,” says Dr Valentina Vitiello, specialist in medical robotics at Imperial College London. Ranzani and his team “know what their system can do, but now they need to really put it into practice”, adds Vitiello.

If this new octopus arm succeeds in future clinical trials, the tides may soon be turned so that the dreadful monster of the seas can come to our rescue.

Margaux Lesaffre is studying for an MSc in Science Communication

Images: Key West octopus by Joe Parks (Flickr, Creative Commons); Granular jamming (Wikimedia, Creative Commons)

Citation: Ranzani, T. et al. (2015)  A bioinspired soft manipulator for minimally invasive surgery. Bioinspiration & Biomimetics, 10, doi:10.1088/1748-3190/10/3/035008

Link: EU Stiff-Flop programme