The eight-armed, double-tentacled cuttlefish is a natural wonder of the deep. This group of intelligent marine creatures are not in fact fish, but rather molluscs that belong to the cephalopod class which include squid and octopus.
Like many cephalopods, cuttlefish have skin pigments which change colour, allowing them to camouflage against any background to hide from prey, attract mates, and communicate with fellow cuttlefish.
These and other fascinating traits are inspiring a huge range of biomimetic technologies. Biomimicry is the practice of taking natural, evolved mechanisms found in ecosystems or organisms and replicating them artificially to solve problems in engineering and design.
By copying the elegant, energy-conserving efficiencies found in wildlife, biomimetic technologies often serve sustainability goals. Millions of years of natural selection often mean that animals are able to use resources efficiently in a number of surprising ways.
Replicas of biological mechanisms often call for bio-based materials because their suppleness is able to mimic the pliability of living organisms that enables them to carry out complex functions.
Below, we look at how researchers are studying different cuttlefish body parts and applying them to sectors like renewable energy, robotics, and architecture.
Cheaper wind-power through cuttlefish fins
Cuttlefish, like rays or flatworms, use slow undulating motions through their muscles to move through water. The startup Undula Tech has now translated these movements into a wind power-capturing device that won the 2019 Biomimicry Institute’s Global Design Challenge.
Undula Tech’s innovation is a prime example of how biomimicry can lead to advances in sustainable technologies. It came up with a power generation device called the Undula Generator which is meant to replace the traditional turbines we use today to harvest wind energy.
The Undual Generator looks very different to the bladed turbines we associate with the wind energy sector. It consists of unevenly spaced struts joined together with stretched pieces of fabric, attached to low poles. The fabric stretched between the struts are what imitate the form and function of cuttlefish fins. It was awarded a patent in 2020.
When flowing water or mind passes over this fabric, it creates a drag force. This is the forces that makes the structure undulate, just like the fins of a cuttlefish, which then rotates a generator to create power.
Usually, wind turbines have to be mounted on tall structures that face the wind head-on to harvest maximum energy. The Undula Generator’s shape and design means it can maximise energy harvesting from wind even when closer to the ground. This means that it can be mounted on residential houses, along road-ways or in tunnels – a handy feature that could maximise the area that wind energy could be rolled out over.
The startup wants to improve the design of their fabric wind power generators. One possibility is to study the fins of a Manta Ray, an animal that covers much longer ocean distances than the cuttlefish. The energy-maximising capabilities of the Manta Ray could open the possibility of an even more cost effective wind and water power generator.
Colour-shifting walls
The cuttlefish can blend into its surroundings almost instantly using just muscle contractions. It has around 20, 000 pigment cells per square centimetre of skin, giving it a fine-grained pixel display that can imitate almost any background convincingly. This sensing-reacting organ is so sophisticated that we could say it holds cognitive capacities.
Researchers are reverse engineering this ability to create colour-shifting ‘smart materials’ that could be embedded into architectural and urban design features.
Rutgers University researchers created a 3D-printed smart gel that imitates the muscle action of a cuttlefish and which changes shape when exposed to light. The muscle-imitating action was supplied by a nanomaterial that contracts in the presence of light. When they applied this smart gel to a stretchy material, it became a display.
One application of a cuttlefish-inspired smart material could be as flexible LCD screens. This would push digital hardware beyond the confines of the mined minerals that dominate our TV screens and laptops. It could also have potential uses as artificial camouflage, smart clothing, in bio-based health monitoring sensors, or as biological light sources.
This technology is still far from commercialisation however since we still haven’t found a practical way around the high heat source required to activate these bio-inspired displays.
Yet the basic idea at work behind these light-activated pigments might have even more profound applications in bio-robotics and neurobotics, sub-fields of robotics that re-create the physical motion and cognitive abilities of living organisms.
A team led by Professor Cunjiang Yu of Pennsylvania State University last year published a study reporting that they had formed a rubbery smart material that copies the cuttlefish’s skin in every way, not just its physical reflexes but its cognitive ones too.
“Although several artificial camouflage skin devices have been recently developed, they lack critical noncentralized neuromorphic processing and cognition capabilities,” said Professor Yu.
The team filled their rubbery skin with semiconductors made from elastic materials that could swap messages between each other at a system level, mimicking the way brain synapses work.
Toothy sensors
Almost every part of the cuttlefish’s physiology opens new vistas in material design. Even its teeth have unusual properties, as Pennsylvania State University scientists found in 2019.
The cuttlefish’s teeth are found in its tentacles, allowing the animal to grip to surfaces. They are arranged in small rings that look fearsome close up.
The teeth are made from special proteins. When samples of this material are lab-cultivated, their microscopic structures can be rearranged to yield new materials with different properties.
Some of these new arrangements produce smart materials which respond to environmental shifts by changing colour, opening the way for wearable health sensors that respond to dangerous chemicals around the wearer or shifts in their physiological metrics.
These do not exhaust the possibility of cuttlefish teeth fabrics. Certain arrangements of the protein in their teeth could produce materials that can conduct electrically or repair themselves once damaged.
Unlike nylon and polyester, the two most heavily produced fashion textile fibres in the world, these protein materials are biodegradable. Lab-cultivated textiles made from them could offer alternative clothing materials that break down into harmless compounds in nature.
Underwater eyes
Cuttlefish eyes are also proving a treasure trove of technological innovation. These animals can hunt in dark underwater environments and roboticists want to understand how they do so in order to improve artificial sensors for drones and self-driving vehicles.
Chinese roboticists early this year published a paper describing how they modelled the cuttlefish eye to build artificial vision devices that can capture images in low-light conditions. They coped the eyeball and visual system of the mollusc, right down to its W-shaped pupils.
The cuttlefish is able to see in the dark accurately by rendering the world in high contrast. A lot of this is down to its curved retina that has a sensitivity to polarised light. Its ability to filter out polarised light allows the animal to picture the world in high-contrast and so better pick out objects in their field. The artificial cuttlefish eye replica used a flexible polarising material as a surface liner.
The researchers found that their cuttlefish eye immensely improved on a current robotic visual system picking up on more details and better able to identify vague outlines as definite objects. Their challenge now will be making a commercially viable cuttlefish eye system using more cost-effective materials than in their lab mock-up.
Cuttlefish skin for high-impact safety
Cuttlefish have a highly porous, oval-shaped bone running through their jelly-like bodies. The material is rigid yet flexible thanks to its cellular structure.
The inside of a cuttlefish bone is easy to crush and scrape away. Yet this porosity gives it a hidden strength. The cells that make up the cuttlefish’s bone might seem fragile and porous but stacked on top of each other, the layers acquire a cushioning power that protects the bottom rows from impact damage.
A research team at Zhejiang University replicated versions of the cuttlefish skeleton.
The team found some could withstand up to 20, 000 its own weight in deformation. One model showed 20-25 times more energy absorption than polymeric foams usually used.
This is all down to the cushioning effect that the stacked bone cells provide, which buckle gracefully under mechanical stress.
The cuttlefish bone isn’t much to look at and is often found sold in pet shops as a bird feed supplement. Yet the humble material could hold applications for safety features in aerospace and heaty-duty vehicles.
The cuttlefish bones might have uses in the building sector too. In crushed form, this renewable material could be added to foam concrete, an insulation material used in construction, to reduce the materials’ overall environmental impacts. Harvard researchers found that very small amounts of the cuttlefish bone additive enhanced the foam concrete’s strength, cutting back on the amount of carbon-intensive concrete that would have to be used.
With all these ingenious traits, the cuttlefish is a gift that keeps on giving. Their powers don’t just end there – cuttlefish have survived hundreds of millions of years, far longer than we have. Most species of the cuttlefish group have managed to weather human impacts on the seas and are still classified as non-threatened.
Yet all this could change. Rising ocean acidification caused by increasing carbon dioxide in the atmosphere are making them smaller and weaker. The cuttlefish’s future hangs in the balance, serving as a potent reminder that the strength of the bioeconomy relies on conserving natural biodiversity. Human-driven marine wildlife loss does not just threaten sources of human food and a repository of natural wonder but will also limit our scientific and technological toolkit.
