Biomimicry is an innovation method that has already had resounding success during its history. We invite you here to review the five most emblematic examples which have contributed to making biomimicry known as a successful method of innovation to the general public.
The first emblematic example of biomimicry: Velcro
Velcro, a very famous technology
Velcro is arguably the most famous example of biomimicry. It is a closing system with a simple mechanics: on one side a surface on which are arranged hundreds of small hooks, on the other surface hundreds of small curls cover it. When the two surfaces are pressed together, the hooks grip the loops and form a reliable, reversible and solid closure system. It is a system that has the advantage of being able to be undone quite easily if sufficient force is exerted, while being perfectly reusable. Depending on the materials used for the hooks and loops, Velcro is capable of withstanding impressive forces: did you know that a square of 5 centimeters of Velcro side is capable of supporting 80kg! These properties have given Velcro a wide variety of applications, ranging from school sneakers to NASA shuttles!
Burdock: the biological inspiration behind Velcro
Velcro is an exemplary case of biomimicry as it relies on the burdock dissemination technique, a common plant on the countryside. The fruit of burdock, which contains its valuable seeds, is covered with small hooks. When passing furry animals, burdock fruits cling to their fur and are thus disseminated at distances of several tens of kilometers: an ingenious way for an immobile plant to conquer new territories by exploiting the mobility of animals! This dissemination strategy is called zoochory, and was directly at the origin of the invention of Velcro through biomimicry.
How and by whom was Velcro invented?
In 1941, the Swiss engineer George de Mestral returns from a hunting trip. His dog, Milka, who spent her morning hanging out in the brush, has her hair densely covered in burdock fruit. Removing them one by one requires George de Mestral a lot of patience. He had all the time to observe the operation of those tenacious little fruits. Out of curiosity, he analyses some of them under the microscope and notices that their hooks are deformable and return to their initial position when plucking them from the hairs. That's how he got the idea to make a quick closing system, which will become one of the most emblematic examples of biomimicry!
The second key example: the Shinkansen
The Shinkansen, an aerodynamic Japanese train
The Shinkansen, famous Japanese train, forerunner high-speed lines, is undoubtedly the second most emblematic example of biomimicry. Circulating at more than 300 km/h, it is one of the most reliable trains in the world. On the island of Honshū, it connects the districts of the Tokyo agglomeration (the most populated city in the world with its 37 million inhabitants), to the cities of Nagoya and Osaka in a very dense urban continuum and more importantly, in a very rugged geological environment. The route of the Shinkansen lines therefore includes many tunnels to cross cities and mountains. However, it turns out that every time it entered a tunnel at high speed, the Shinkansen generated a shock wave causing significant noise pollution. However, in the context of very strong urbanisation of the Japanese population since the end of the Second World War, the problems of noise pollution have become increasingly important over time. Since the 1980s, it became essential to find a solution to the noise pollution of the Shinkansen in such a densely populated area.
The kingfisher, the origin of the optimisation of the Shinkansen
The kingfishers (Alcedinidae family) are birds found on all continents except Antarctica. They are specialised in stalking fishing: they spend much of their time perched above shallow water and dip their beaks forward to grab small fish that venture close to the surface. A true concentrate of technologies, the kingfisher has, among many other things, an eye capable of correcting chromatic aberrations caused by light reflecting in the water. This allows him to see very clearly what is happening below the surface when we only see a reflection of the sky. However, what allowed the Japanese engineers to solve their problem is the shape of its beak. Indeed, when they split the surface of the water, these small birds manage to generate almost no splash, which allows them to reach prey more than twenty centimeters from the surface with greater speed and discretion. In calm weather, when the water surface is smooth, their hit rate is 100%. The secret of this hydrodynamics lies in the shape of its beak: long, thin, spearheaded, and streamlined in perfect continuity with the shape of his skull. It is this mouthpiece which, through biomimicry, enabled the Shinkansen engineers to solve the problem of noise pollution.
In particular, Eiji Nakatsu, railway engineer who worked on the Shinkansen project, is behind this biomimicry innovation. Also an ornithologist, he had observed the kingfisher in fishing action. He noticed that the Shinkansen and the kingfisher shared similar constraints: the bird's beak, like the front of the train, suddenly encounters strong resistance. By using biomimicry, he was inspired by the shape of the beak of the kingfisher, to redesign a new nose for the Shinkansen. And the models he made confirm that this option was the right one. When it entered service in 1997, the Kingfisher-inspired Shinkansen 500 offered:
A reduction in the boom at the entrance to the tunnels and a quieter running in general;
A 15% reduction in power consumption;
A 10% speed increase.
This is an iconic example of biomimicry. It highlights one of the essential components of innovation in general, and of biomimicry in particular: multidisciplinarity. It's because Eiji Nakatsu was both an engineer and an ornithologist that he managed to transpose what he observed into an industrially applicable solution through biomimicry.
The lotus' hydrophobia: one of the best-known examples of biomimicry
The Lotus
The sacred lotus is a water flower prevalent in a large majority of Asia. Lotuses live in colonies in shallow water. They often create a rich ecosystem of amphibians, birds and insects: their large leaves form a carpet on the surface of the water on which many organisms move by depositing solid bodies (mud, excrement, particles, etc.). However, the lotus depends on the photosynthesis of its leaves to survive. If particles prevent light from reaching the surface of its leaves, or limit it in places, it will result in a lower energy performance. Evolution led the lotus to develop an elaborate technique to optimise its energy performance: superhydrophobia. The principle is simple: the lotus leaf's surface structure prevents adhesion of particles and water, the slightest drop of water carries with it all the dirt on the surface of the leaf. Thus, the lotus leaf surface is self-cleaning. It is this feature that has inspired many innovations within biomimicry.
The lotus effect: what is it?
The lotus' superhydrophobia has been known for centuries but could only be explained with the invention of the electron microscope, it was only once it was understood that it could be at the origin of innovations by biomimicry. In the 1970s, the German botanist Wilhelm Barthlott solved the mystery. This is explained by villi on the surface of the leaf, themselves covered with micro-villi. This double villi structure creates a nano-scale roughness which creates very few contact points between the drops of water and the leaf and the drop “slides” over the surface, carrying with it all the micro-particles of dust or dirt. It is this nanometric structure that has inspired numerous biomimetic applications.
Hydrophobia on lotus leaves versus water lily leaves
This discovery de Wilhelm Barthlott gave birth to industrial applications as of the 1990s. Applications can be found in many sectors: self-cleaning paints for facades in construction, coatings for hydrophobic glass, superhydrophobic textiles and synthetic leathers, etc. Recently, solar panels reproducing this particular nanometric structure of the lotus, have been developped to obtain the self-cleaning hydrophobic effect and, like the lotus leaf, to optimise their capture of solar energy.
Since the discovery of the lotus effect, we have noticed that many other plants have similar properties such as nasturtium or… leek!
Shark skin: the 4th leading example of biomimicry
Sharks: a rich biological organism for biomimicry
Sharks have colonised all the seas and oceans of the globe. There are about 500 different species. There are many reasons for this evolutionary success. Their highly developped olfactory system allows them to spot their prey from great distances underwater. In addition to this sense of smell, they are equipped with sensory organs called “Ampullae of Lorenzini” that allow them to detect electromagnetic fields present in water as well as temperature gradients. They are thus able to spot a muscle contraction and therefore locate their prey. But there's another characteristic of sharks that gave them an advantage: their ability to move easily in water. While not all sharks actually have a hydrodynamic shape, they do have an amazing feature that allows them to greatly increase their ability to move through water with little energy expenditure: the structure of their skin.
The hydrodynamics of shark skin
Unexpectedly, the shark skin is very rough to the touch. Contrary to our intuition, hydrodynamics are not optimised by a perfectly smooth surface. On the contrary ! Shark skin is actually made up of a myriad of small scales which are entangled. These small scales have the particularity of having micro-grooves on their surface, which generate a sort of “film” of water which limits friction of the shark's body with the fluid. This is called a flow control technique. This is what reduces friction and allows the shark to move at low energy cost.
This amazing structure has spawned a wide variety of applications in hydro- and aerodynamics. Aeronautics, is no stranger to biomimicry, took advantage of this opportunity. The aircraft manufacturer Airbus was inspired by it to develop a coating for aircrafts intended to reduce fuel consumption. The tests were very conclusive and allowed to reduce drag by 10%: which would result in fuel savings of more than 1% ! It's colossal! In 2019, Airbus announced the upcoming commercialisation of this coating which is a very eloquent example of biomimicry.
But that's not all! Biomimicry has found other applications for this amazing structure of the shark skin. The scale microstructure has a height to width ratio that prevents the attachment of microorganisms, and their overgrowth. An American company, Sharklet Technologies, was inspired by these micro-grooves to create a structurally antibacterial surface. Groove pattern and size (2 microns wide and 3 microns high) prevents bacteria colonies from adhering and colonising the surface. The applications of this technology are very promising in the medical sector: for example for dressings, adhesive films (to protect surfaces), catheters, etc. Depending on the type of surface, the proliferation of bacteria is reduced by 70 to 97%!
Biomimicry made it possible to imagine other applications to this shark skin structure. For the creation of swimsuits, or the design of antifouling coatings for boat hulls. After a long stay in the water, micro-organisms develop on their hull (submerged part). These can increase the drag of a boat by 30% to 50%! Today the fairing is expensive and requires the use of harmful chemicals to clean the hull and repaint it. An antifouling structure inspired by shark skin could allow better efficiency with much more limited use of chemicals!
Here is another example of biomimicry that shows the diversity of applications that can be inspired of a single characteristic of life!
Gecko Skin: Latest Iconic Example of Biomimicry
The Gecko
Do you know about geckos? They are little nocturnal lizards that often surprise us on summer evenings behind the shutters of houses in the south of France. Big eyes, a stocky body, star-shaped paws with thick fingers, and always upside down. There are many species, spread out on all continents and with very different looks. Some have the ability to copy the shape of their support to camouflage themselves, a strategy called mimicry. But they all share a common characteristic: the amazing ability to be able to walk on any vertical or sloped surface as comfortably as we can on level ground. It is not uncommon to see them running along the walls or even on a window!
Gecko's paw grip
The secret to this ability lies in the structure of their legs. Or rather… the hairs of their paws. Indeed, the fingers of geckos are covered with very dense microscopic hairs: the setae. There are several thousand of them per mm². Each of these hairs is branched at its end into several other small even finer hairs. The density of hair leads to an interaction on the molecular level with the support on which the gecko evolves. This molecular interaction is called “Van der Waals force”. It is a low intensity electrical interaction between atoms that creates an adhesion between the setae and surface. Thanks to these millions of hairs, the gecko is able to walk on any surface. And it is this characteristic that biomimicry tries to exploit.
These hairs were discovered in 2005! Since 2005, many biomimetic innovations took inspiration from this principle to look for solutions for reversible adhesion. For example miniature robots capable of climbing on glass, or Geckskin, a structural adhesive, stickable/peelable, without adhesive substance or chemicals, which holds only by the force of Van der Waals. The gecko is famous in biomimicry because of the significant amount of ongoing research that is inspired by the structure of its legs, and by the promising prospects offered by movement on any surface. In 2015, a Stanford researcher managed to climb a glass wall thanks to an assembly of adhesive plates inspired by the paws of the gecko.
These 5 emblematic examples of biomimicry are the best known to the general public, and are invariably found in all popular publications on biomimicry. They are indeed eloquent, but they are only the tip of the iceberg. Indeed, there are thousands of other bio-inspired technologies already developped, and many more to be invented!
Biodiversity is an endless source of inspiration for innovation. Biomimicry is still very new in research and innovation methodology, which largely remains to be explored.
Comments