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Written by: Jane Li
Written on: March 21st, 2017
Tags: biomedical engineering, health & medicine, lifestyle, material science, mechanical engineering, water, physics
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Jane is an animal-loving sophomore studying Arts, Technology, and the Business of Innovation in the Iovine and Young Academy at USC.
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Volume XVIII Issue I > From Shark Skin to Speed
Sharks inspire a feeling of awe in many people, partly due to their natural speed and representation of power. Through modern biomimicry, scientists have been able to imitate shark skin and design speed-enhancing technologies to benefit transportation, medicine, and apparel design.
biomimicry

Introduction

When visiting a local aquarium, there is no lack of spectacles that may capture one’s attention – glimmering schools of sardines swimming as a unit, colorful sea dragons hiding among aquatic plants, and most delectably, the distinct aroma of the fish and chips served in the food court. One sight, however, stands out from all other marine organisms: the shark. Humanity has long perceived sharks as an animal of power: grand yet sleek, inspiring awe among zoologists and the casual beachgoer alike. With new stories reporting shark attacks every year, even a student in elementary school knows that the shark is an animal that deserves respect.
One characteristic that adds to the shark’s magnificent reputation is its speed; although sharks are relatively large mammals, they are able to swim up to 43 miles per hour in short bursts [11]. This speed comes from 3 billion years of evolution and natural selection, allowing them to capture prey efficiently and achieve an image of dominance in the underwater ecosystem [3][4]. Though the human race places high value on speed for different reasons – convenience, efficiency, and productivity – scientists are looking to this underwater powerhouse for inspiration behind new designs and technology.

What is Biomimicry?

Of course, sharks are not the only organisms that scientists study and strive to imitate. Because nature is essentially a 3-billion-year-old research and development lab. Scientists, engineers, and designers have relied upon natural organisms and processes for hundreds of years in order to spark innovation [1]. Biomimicry is this process of studying and replicating systems in the natural world, and it ranges from watching birds to achieve flight to imitating gecko feet to create adhesives [2][3]. One of the earliest and most recognizable examples of biomimicry, mentioned in Fig. 1, was George de Mestral’s invention of burs to create Velcro in 1952 [3]. George de Mestral, a Swiss engineer, was on a hunting trip in the Alps when he noticed that tiny burs covered the fur of his dog [3]. He studied these burs closely and used them as inspiration to create an equally gripping material called Velcro [3]. While the term “biomimicry” did not yet exist, Velcro would soon become one of its most successfully commercialized examples [3].
Bunakenhans.com, Sites.psu.edu/Bunake​nhans.com, Sites.psu.edu
Figure 1: Major Biomimicry Events. (Modified from [2][3]).
The first appearance of the term “biomimicry” occurred in 1982, decades after the development of Velcro, and was not widespread until after scientist and author Janine Benyus used it in her book, Biomimicry: Innovation Inspired by Nature [2]. The book’s publication led to the growth in popularity of biomimicry, and more and more scientists, designers, and engineers began looking towards the natural world for inspiration. For example, in the 1990s, Eiji Nakatsu, an avid bird-water and engineer, observed the silent and clean-cut act of a kingfisher catching prey, and decided to implement that level of precision into his work, leading him to design a more energy efficient, noise reducing, and fast form of transportation: the Japanese Shinkansen Bullet Train [3]. Similarly, in 2005, Mercedes Benz released a new model named Bionic, shown in Fig. 2, a car designed after the boxfish, sculpted to be aerodynamic and extremely efficient for a car of its size [3]. Comparable to the efficiency of the kingfisher and the aerodynamics of the boxfish, the speed of sharks – generated by their skin – continues to inspire many recent innovations.
Environment-ecology.​com/Environment-ecol​ogy.com
Figure 2: Mercedes Benz Bionic (Modified from [15][16]).

Shark Skin Technologies

While many natural processes associated with sharks are fascinating, experts are especially interested in shark skin and its ability to increase speed [8][10]. The science behind shark skin speed is fairly simple: When an object is moving underwater, water flowing at the surface of the object moves more slowly than water moving away from that said object [9][Fig. 3]. On smooth surfaces, this contrast of water speed surrounding the object causes the fast-moving water to break up into many turbulent vortices, which slows down the overall speed of an object moving underwater [9]. Shark skin reduces this speed discrepancy, which in turn reduces turbulence, and allows greater speed [10].
Massbayguides.com, Asknature.org/Massba​yguides.com, Asknature.org
Figure 3: Shark Skin Dermal Denticles & Water Movement (Modified from [17][18]).
Under a microscope, shark skin is composed of many tiny, overlapping scales called dermal denticles or “little skin teeth,” depicted in Fig. 3 [7]. Each dermal denticle has microscopic grooves running along it longitudinally, in alignment with water flow when the shark swims forward [7]. These little grooves speed up slower water by pulling faster water around the shark onto the shark’s skin and mixes it with the slower water, bringing up the average speed of water on the shark’s skin [9]. Denticles also channel the flow of water and cut up sheets of water traveling over a shark’s skin and breaking it up into smaller, less turbulent vortices [9]. Ultimately, the dermal denticles on shark skin averages out the speed of water surrounding it, causing less turbulence, so that the shark can glide through water at a greater overall speed [9].

Applications

The study of shark skin and its unique composition has led to many scientific breakthroughs, most of which are categorized into advancements in transportation, medical strategy, and apparel design.

Transportation

Perhaps the most obvious application of shark skin inspired technologies is for transportation. Yvonne Wilke, Volkmar Stenzel, and Manfred Peschka, scientists from the Fraunhofer Institute, a German research organization, developed a type of paint inspired by studying the dermal denticles of shark skin that goes on as the outermost coating of airplanes, adding no additional weight [12]. However, in order to achieve the structure of shark skin, the paint must actually go evenly in a thin layer over a stencil, rather than directly onto the plane [12]. Researchers claim that when this special shark skin paint coats every single airplane in the world, it can save up to 4.48 million tons of fuel per year [12].
This energy efficiency does not stop at airplanes; other forms of transportation such as ships and cars also benefit from the innovative shark skin paint. The Fraunhofer Institute research team reduced over 5% of friction in a ship construction test using the shark skin paint [12]. According to this data, over the course of one year, their shark skin paint could save one large container ship up to 2,000 tons of fuel [8]. Following this innovation, a company called SkinzWraps has created a shark skin coating for cars [8]. Although their statistics have not yet been confirmed by a third party, SkinzWraps boasts an 18-20% improvement in the MPG of an average car, offering an extremely high level of fuel efficiency for the average consumer [8].

Medical Field

After utilizing shark skin to increase the speed of everyday objects, scientists began to look into shark skin biomimicry for medical advancements. Because of its rough texture, shark skin discourages parasitic growth like algae and barnacles [7]. Similarly, shark skin-inspired surfaces prevent bacteria and microorganisms from holding on to them for long periods, ultimately resisting bacteria growth [9]. Due to this unique trait, medical administrators are bringing shark skin surfaces into hospital atmospheres as a preventative strategy [7]. Sharklet Technologies, a biotech startup that specializes in making germ-deflecting surfaces, has created a plastic sheet that can adhere to hospital walls in order to prevent dangerous bacteria from reaching ill patients since it cannot stick to or spread via the covered walls [9][14][Fig. 4]. One test in a California hospital proved that for three weeks, Sharklet’s plastic sheeting surface prevented microorganisms like E. coli and Staphylococcus A from establishing colonies that were large enough to infect humans [8]. According to Mark Speicker, the CEO of Sharklet, their plastic surface can cut bacteria by up to 99.99%, ultimately saving thousands of lives [14].
Stethoskin.com, Modip.ac.uk/Stethosk​in.com, Modip.ac.uk
Figure 4: Sharklet Technologies w/ Zoom In Graphic (Modified from [19][20]).

Fashion

Unlike the transportation and medical fields, the fashion industry experienced less direct advancements using shark skin-inspired technologies. In the 2008 summer Olympics in Beijing, Michael Phelps received media attention for his shark skin-inspired swimsuit, represented in Fig. 5 [7]. Before the 2000 Olympic games, Speedo had already developed a line of shark skin inspired swimsuits called the Fastskin line [10]. During that year’s swimming competitions, 80% of medals won were awarded to swimmers wearing Speedo’s Fastskin suits, and of the 15 swimming world records broken, 13 of them were achieved by swimmers wearing Speedo’s sharkskin suits [10]. One of Speedo’s sharkskin swimsuits, a full body suit called the LZR Racer, was so successful that the International Swimming Federation (FINA) outlawed it by banning zippers and restricting the coverage of a men’s competition suit from navel to knees [7][21].
Popular Science/Popular Science
Fig. 5: Michael Phelps Wearing Speedo’s Fastskin Suit [13].
However, even with such success, experts such as George Lauder, a professor of ichthyology (the study of fish) at Harvard, claim that sharkskin suits do not actually reduce drag [13]. According to Lauder, shark skin only reduces drag when attached to a flexible surface [13]. Human bodies are much less flexible than those of sharks, so a sharkskin swimsuit does not benefit a human swimmer in terms of drag reduction [13]. Therefore, while Speedo originally modeled the Fastskin line after shark skin, evidence suggests that its success is simply a byproduct of experimentation, not due to the similarity to shark skin.

Conclusion

Ever since the term “biomimicry” emerged, scientists all over the world have intensely studied biological systems, experimented with new ideas, and attempted to create innovations molded from nature. In just this limited example, through the biomimicry of shark skin, scientists have created more efficient processes in transportation, medicine, and athletics. Biomimicry of other natural phenomena could inspire just as numerous and diverse engineering applications. Additionally, as Speedo’s Fastskin line suggests, biomimicry can lead to unexpected innovations and spinoff technologies that can succeed even if not adhering to strict biomimicry – promising that unexpected innovations and spinoffs from studies of biomimicry can also spark new ideas and affect the future for any field.

References

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