David Tolfree, physicist and independent technology consultant, and Dr Alan Smith, materials scientist and independent technology consultant
Mobility is an intrinsic part of human development. Early humans survived and progressed because they were able to migrate across the world, first by foot and later by improvised mechanical means. The wheel, although not initially used for mobile transport, was adopted later for that purpose and is still the basic component of ground-based transport. Perhaps early humans observed animals using round stones or pebbles to move objects.
Over hundreds of millions of years, animals have evolved designs that are fit for purpose. Many have been directed at minimising energy and reducing weight to expedite efficient motion. This is especially true of birds in terms of their defying the force of gravity to achieve flight.
In this article, various transportation systems that have been influenced through the observation and study of animals are described. The most well-known, and perhaps most significant, is the aircraft, which was inspired by birds in flight.
Optimised design
Spherical- and dome-shaped designs maximise internal volume for a given surface area and conserve material. Birds and reptiles produce eggs that have rounded geometries since they must survive unprotected outside the body and sometimes in harsh environments. Humans and monkeys have rounded heads to accommodate their larger dome-shaped brains.
As has been learned from nature, structural design is crucial. Our bones are a good example of how nature has provided a material that is lightweight and tough. The average person has a skeleton that is 15 percent of their body weight, whereas a frigatebird, weighing just over a kilogramme and with a wingspan of two metres, has a skeleton that is only five percent of its body weight; this ratio is essential when flight is a factor. All bones are strong lightweight nanostructures. As humans could not fly unaided, they had to develop lightweight yet structurally strong materials to produce aircraft.
Today, aircraft are manufactured using aluminium and ultra-lightweight carbon- and titanium-based composites containing nano-particulates. This enables them to deliver significant fuel and cost savings.
An example of weight saving on aircraft being linked directly to fuel and cost savings has been provided by The SAVING Project, a consortium of seven organisations that aims to develop sustainable products through design optimisation and additive manufacturing (AM). The consortium redesigned and additively manufactured a seat belt buckle in titanium, which weighed just 68 g, compared with the traditionally manufactured seat belt buckle in steel, which weighs up to 155 g. It was worked out that on an Airbus A380 with 853 seats, replacing traditionally manufactured buckles with additively manufactured titanium buckles would mean a total weight saving of 74 kg, which over the aircraft’s lifetime represents a fuel saving of 3.3 million litres and a reduction of 0.74 million tonnes in CO2 emissions1.
Weight saving is also a critical issue for space vehicles. According to the NASA Marshall Space Flight Center (MSFC), “it costs US$10,000 to put 1 lb (0.45 kg) of payload in Earth orbit”2. In 2015, Kjell Lindgren, a US astronaut, took custom-made plastic bagpipes onto the International Space Station (ISS) to play the hymn Amazing Grace as a tribute to Victor Hurst, a research scientist involved in astronaut training, after he passed away. The cost of transporting the bagpipes is believed to have been around US$54,600–259,0003.
Surface modification
In 2006, the company Speedo marketed a full body swimsuit called Fastskin, made of polyurethane woven fabric and textured to be like shark’s skin. This texture, which enables sharks to move so rapidly, has v-shaped grooves that reinforce the direction of water flow. Today, there is a range of Fastskin swimwear that protects swimmers and aids their motion in water.
Furthermore, aircraft and marine manufacturers have reduced drag by modifying surfaces that mimic shark skin. Skin friction is responsible for around half of the total drag on an aircraft. Airbus reduced drag on an A340 aircraft by 10 percent by using sheets of a ribbed structure in the longitudinal direction on the plane. The designers of submarines and surface vessels have also studied the skins and geometries of marine creatures such as dolphins, seals and whales to improve mobility and manoeuvrability in water.
The bumpy, anti-reflective pattern on the surface of moths’ eyes has spawned a variety of products used in bright sunlight applications. If the moth did not have anti-reflective eyes, then its predators could much more easily make a meal of it. The surface of the eyes’ structure is such that light hitting it bounces off the microscopic bumps, thus preventing direct reflection (figure 1), as happens with cats’ eyes used for road markings. Anti-reflective surfaces are now used for the screens on cameras and mobile phones. The car-maker Audi used this technology early on for the dials of its TT Roadster, enabling them to be seen in bright light conditions.
Figure 1: Moths' eyes have a bumpy, anti-reflective surface.
Just as our own wounds heal themselves naturally, there are plants that can do this as well. Dutchman’s pipe and black sarsaparilla are known for their rapid recovery if they are damaged. A number of car manufacturers are developing self-healing paints that similarly repair themselves if scratched. This involves so-called autonomic healing of the polymers in paint.
The main and most important consituent of paint is the binder or resin, it being responsible for: binding all the other ingredients, such as additives, pigment and solvent, together; binding these ingredients to the surfaces they are applied to; and ultimately formation of the paint film. The binder is formed by using a catalyst to speed up the reaction between monomers and thus produce long polymer chains—a process known as polymerisation. In the case of self-healing paint, some of the monomers in its surface are encapsulated; if the paint is scratched, these capsules are broken and the released monomers polymerise due to being exposed to the catalyst in the paint, thus filling the scratch and returning the surface to its original state (figure 2).
Figure 2: The autonomic healing process of paint.
Vehicle designs
Aircraft
More than any other animal, birds have inspired aircraft designs. Gliders, monoplanes, biplanes and helicopters are examples of such aircraft. A notable example is the Northrop Grumman B-2 Spirit or Stealth Bomber, an American military aircraft capable of achieving speeds of up to 1,010 km/h. The profile of this aircraft is believed to have been influenced by the peregrine falcon4
Drones
The biomechanics of insect-inspired flight systems is an important field of study, especially for drone development, where it is necessary to generate sufficient aerodynamic forces to stay airborne while controlling flight autonomy.
For millions of years, nature has evolved miniature autonomous flying insects that can navigate in harsh windy environments, avoid collisions and survive crashes—abilities lacking in existing drones. Research and development for the next generation of drones is being actively pursued by many civil and military research laboratories. Known as micro air vehicles (MAVs), these insect-like drones will be designed to achieve complex manoeuvres and operate at low speeds5.
Animal Dynamics—an Oxford University spin-out company in Yarnton, UK—is developing a small drone based on the flapping wings of a dragonfly6. Known as Skeeter, the drone weighs less than 30 g and can fly for longer than any other drone. Dragonflies owe their incredible agility to independent muscles on each of their four wings, which enable them to manoeuvre and glide more than any other flying creature (figure 4). The Skeeter, assisted by the latest sensor technologies and Global Positioning System (GPS) navigation, is expected to revolutionise small-scale drone designs for use in applications such as monitoring and surveillance.
Figure 4: A dragonfly
Cars
The Mercedes-Benz Bionic is a concept car first introduced in 2005. It is modelled on the yellow boxfish, which has a very rigid exoskeleton and body shape, affording a low coefficient of drag (figure 5). The car boasts 80 percent lower nitrogen oxide (NOx) emissions than the average car and selective catalytic reduction technology.
Figure 5: The Mercedes Benz Bionic concept car, inspired by the yellow boxfish.
Trains
Every day, millions of people in Japan rely on the nine Shinkansen bullet train lines operated by Japan Railways Group (JR Group). These lines cover nearly the entire country, and the oldest, known as Tokaido Shinkansen, is believed to be the busiest high-speed rail line globally.
At one time, loud booms could be heard up to 400 m away as Shinkansen trains emerged from tunnels due to air pressure build up, giving rise to numerous complaints. Eiji Nakatsu, an engineer and former director of technical development at West Japan Railway Company (JR-West), managed to solve this problem in the mid-1990s thanks to biomimicry. An avid birdwatcher, Nakatsu took inspiration from the kingfisher in his quest to put an end to the so-called tunnel boom7.
A streamlined beak enables the kingfisher to dive arrow-like into the water—barely creating a ripple, let alone a splash—and spear unsuspecting prey (figure 6). It moves quickly from the air, a low-pressure medium, into the water, a high-pressure medium. This is similar to how the trains move at high speed from the open air, low-pressure, into the tunnel, high-pressure. The kingfisher’s beak, which increases incrementally in diameter from the tip to the head, allows it to overcome this sudden pressure increase, permitting water to flow past its body rather than be pushed forwards.
Figure 6: A kingfisher diving into water causes minimal disturbance to the surface
Nakatsu led a team of engineers in redesigning the front-end of the Shinkansen 500 series train so that it mimicked the shape of the kingfisher’s beak, eliminating the aorementioned pressure increase and therefore the tunnel boom. Today, the front-end geometries of all high-speed trains are based on that of the Shinkansen. Indeed, other forms of land vehicles as well as air vehicles now possess similar front-end geometries.
Another troublesome noise for Shinkansen trains originated from the pantograph, an apparatus on the roof that connects the train to the overhead power line. In this instance, Nakatsu looked to the owl for inspiration.
A comb-like array of tiny serrations on the leading edge of the owl’s primary feathers segregate large air vortexes to create smaller ones, thereby allowing it (like the kingfisher) to swoop down silently and take prey by surprise. Smaller air vortexes are known to create lesser turbulences, thus reducing aerodynamic vibrations and noise. Nakatsu and his team re-shaped the upper part of the pantograph to resemble the owl’s wings and inscribed tiny serrations along its edges.
The two aforementioned examples of aerodynamics in biomimicry have helped make it possible for Shinkansen trains to travel at 320 km/hr (199 mph) and not exceed the Japanese government’s 75 dB noise limit.
Cycles
A group of students from the Universidad Autónoma de Yucatán (UADY), in Yucatán, Mexico, designed the Mocan non-motorised vehicle for the Biomimicry Institute’s 2013–2014 Biomimicry Student Design Challenge (focused on transportation), securing first place8. The Mocan—intended as a cheap and environmentally-friendly alternative to the traditional motorised cargo bike—looked like a scooter but afforded plenty of room for carrying large items up to 10 kg (figure 7). It imitated the zig-zag movement of millipedes and snakes. Instead of pedalling or pushing, the rider had to move a handle back and forth to enable forward motion.
Figure 7: The Mocan non-motorised vehicle mimics the zig-zag movement of millipedes and snakes
Ships
Penguins release streams of lubricating bubbles trapped in their feathers to help them launch out of the sea onto land or an ice flow. Marine engineers are developing systems that similarly release air to create a carpet of bubbles along the bottom of ships and thus reduce friction in the water.
Studies of traffic flow
Based on studies of the motions of ants and other insects, companies such as United Parcel Service (UPS) have spent hundreds of millions of dollars developing algorithms to optimise routes for delivery vehicles, saving time and reducing fuel costs.
Managing the flow of vehicles is a challenge for many urban planners. After studying the way ants, bees and termites communicate right-of-way in their busy colonies, Dr Ozan Tonguz, a Professor in the Department of Electrical and Computer Engineering at Carnegie Mellon University (CMU) in Pittsburgh, US, has invented the Virtual Traffic Lights (VTL) algorithm to help control traffic on busy streets9. VTL is intended for the locating of traffic lights on car windscreens rather than at intersections. The algorithm uses information collected from GPS devices and other sensors to determine if a driver sees a green, amber or red light on their windscreen.
In simulations, the algorithm managed the flow of cars in much the same way that insects manage themselves. In ant and termite colonies, the large group always gets to go first. As soon as the biggest group is cleared, the next group is allowed to go. Through the simulations, the scientists found that traffic drive time for urban commuters was reduced by 40–60 percent. The next stage in development of the VTL system will take account of pedestrians and cyclists in the flow of traffic. This work will be significant for the control of autonomous vehicles in urban environments.
The future of transport
Current projects that will change the future of transport include the development of autonomous electric cars, hyperloop trains, rocket propelled ships and space planes; these forms of transport will be integral to the infrastructures of future cities. Three of the world’s richest transport pioneers, namely Elon Musk of Tesla (electric cars, space planes and hyperloop trains), Jeff Bezos of Amazon (space vehicles) and Richard Branson of Virgin (space planes and hyperloop trains) are accelerating progress with massive investments in research and development. The full implementation of the new transport systems will require many innovations. Could these come from the further study of animals?
Conclusion
The examples given in the articles published in this and the previous two issues of CMM show how biomimetics has assisted in the realisation of new products and materials from initial conceptual designs. The two most revolutionary are the evolution of flight and the development of drugs for medicine. Both are progressing rapidly as new materials and processes are discovered.
Biomedicine has been the most successful beneficiary of studies from plants, insects and bacteria, but there is still much to learn. The need for new anti-bacterial drugs is one area requiring urgent development. There are many products in other fields—notably domestic appliances and artefacts, furniture design, and materials for fabrics—that have been inspired by nature.
The authors hope that these articles encourage readers to take a closer at nature in order to find innovative solutions to problems. Today, we have taken only a few steps on the long journey of discovery that nature has in store. Readers are reminded that we need animals and plants but they do not need us, therefore their preservation, and of course that of their habitats, is inextricably linked to our own.
David Tolfree, physicist and independent technology consultant
Dr Alan Smith, materials scientist and independent technology consultant
References
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2Advanced space transportation program: paving the highway to space [background fact sheet]. NASA Marshall Space Flight Center. Available at: go.nasa.gov/2RNC2ed
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6Excell, J. (2016). Insect inspiration: UK defence drone mimics dragonfly flight. November 16. The Engineer. Available at: bit.ly/2AKWUcm
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9Ants-inspired virtual lights to beat traffic jams [press release]. November 7, 2012. The Hindu Business Line. Available at: bit.ly/2STJZfm