The Push and Pull Building System, Part 2

    There is another root of structures that extended from nature and it began with Buckminster Fuller. His designs include geodesic domes made from complex webs of triangular and hexogonal units. His designs have also found many echos in natural structures. The geometric structure that he designed is called an icosahedron and it closely mimics the structure that is found in nature: the bacteriophage. The hexagonal/pentagonal sphere is seen not only in the nano world but also in micro, everyday human objects (soccer ball), and now architectural (Fuller's domes).
    An interesting area where biology meets structure is tensegrity. The word was made by Buckminster Fuller but he did not create the concept. The concept is combining tension and integrity. It's a structure that's held together by tension members but maintains it's shape. Below is a tensegrity structure:

    Kenneth Snelson is known in the architectural community for his tensegrity designs. In 2000, he made a sculpture named Dragon (above). At first, the structure seems to defy the law of gravity but under high tension, a cable may look straight but there will always be a sag. 

    It is understandable for some to not see the relationship between biology and architecture. But since nanotechnology is largely hidden from the human eye it is good to have some larger structures in industry that mirror some natural structures from nature. The clean and smooth lines that nature usually presents helped this movement come along and some believe that those qualities helped human industry move more modern. 

The Push and Pull Building System, Part 1

"Steady under strain and strong through tension,
Its feet on both sides but in neither camp,
It stands its ground, a span of pure attention,
A holding action, the arches and the ramp
Steady under strain and strong through tension."
Seamus Heaney, 'The Bridge'

     We see a lot of bio-inspired materials come from tiny forms, but humans were builders far before they were nanotechnologists. Along side the growth of bio-inspired material science is the rise of bio-inspired architecture called Zoomorphic. Famous architects have started to show Zoomorphic in their work including Will Alsop, Edward Cullinan, Norman Foster, and many more.
    The Zoomorphic exhibit created a discussion with architects and scientists on how deep the roots are between organic tendencies. Julian Vincent, Professor of Biomimetics at Bath University, says that he would like to see architects learn the principles of natural structures and apply it. He says that architects are now concerned with designing buildings that use energy efficiently. An example of this is the spiraling latticework of Norman Foster's Swiss Re Tower because the internal spiral wells provide natural ventilation. Designing these things comes with the same problem as designing bio-inspired nanotechnology which is building techniques that are form fitting.
    D'Arcy Thompson wrote about early links between nature and buildings. An early example is in 1851 when Joseph Paxton built the Crystal Palace. It is thought that he got the idea of ribbing from the Victoria regia, a water lily. Thompson pointed out how nature makes these structures by using the least amount of energy possible like a hexagonal pattern from wasps nests, and egg shells, where the whole structure is a curved surface.

    Since early human history the structures of houses were created brick by brick. The struggle came when the use of bridges were needed. Because of the force of gravity, a string or cable that is suspended off of poles will always have a sag in the middle. Building an arch was the solution to this problem. Isambard Kingdom Brunel made an arch bridge as a grand scale when the Great Western Railway had to cross the Thames. His design had the flattest arch in the world and many people thought that it would never work but it is still standing 150 years later.
    The Forth Bridge is a cantilever bridge, a structure that engineers share with nature: the backbones of quadrupeds are cantilevers. In the Forth Bridge the weight is equally balanced which makes it pretty stable. To have a good bridge you need equal parts on compression and tension. The Forth Bridge has some compression and some tension, but tension structures really only entered the builder's era with suspension bridges. The essence of a suspension bridge is to span the complete distance with two hanging cables and then to suspend the deck from these cables with smaller vertical cables.

    Another great invention in the world of architecture was reinforced concrete. Concrete and steel are complementary since concrete is strong in compression and steel is strong in tension. Having a steel grid inside of the concrete enables almost any size or shape to be cast in concrete. Concrete helped architects and engineers design nature's most organic structure: the shell. Heinz Isler has built more then 1,500 shell buildings by using natural forces to find his forms. Even though Isler was unaware of this, the results of his experiments came from the criteria of natural objects which puts them in the mainstream for bio-inspiration. Isler designs his shell buildings by scaling up from his original structure. Their delicacy makes them so unique, classical domes have a thickness/radius ratio of about 1:50. Natural eggshells have a ratio of 1:100. Isler's domes have a ratio of 1:800. Eventually, computers were able to copy this design very easily and that made Isler very angry.
                           Isler's shell design over a filling station on the Berne-Zurich highway

    Santiago Calatrava is currently the leading exponent of organic architecture. Calatrava is both an engineer and an architect . His most famous bridge is Alamillo Bridge. The bridge looks like a giant harp because it has giant cables suspended everywhere. He also designed the 2004 Athens Olympic Stadium. He is known for his beautiful but also extremely expensive buildings such as Zurich Railway Station, Milwaukee Art Museum, Campo Volantin Footbridge, and the Sundial Bridge at Turtle Bay. 

 
    

Origami for Engineers

"At a slight angle to the universe."
Em Foster on poet 'CP Cavafy'

    Nature likes things that can fold away into something small and open out when they are needed. Engineers call these things deployable structures. The umbrella is a perfect example of this. When you press a button, the shaft expands and with doing so the forces help open the spokes that carry the fabric. An umbrella may be a perfect example of a deployable structure but it also shows the key problem with a deployable structure which is that it is not fully automatic. When it opens, the fabric begins to tighten which creates a dramatic increase of force to push it all the way and lock it into place. Once it's locked, you have to apply even more force to be able to unlock it and fold it back up again. Engineers call this a bistable system, which means that changing from one state to another can be difficult. It is hard to design a system that can be fully automatic on its own but it seems that nature has already figured it out. A beetles wing's are a deployable structure because they unfold and open fairly easy and then fold up again when they are not in use.
    In human nature we tend to fold things at right angles. It has come to the point that if we did not fold newspapers or letters at a right angle then we usually create a problem with how these papers are displayed. There is nothing wrong with this but human nature is always about finding an easier way to do things. If we can mimic the folds from a hornbeam and beech leaf then that could be possible. If you were to look at a leaf bud from these trees you wold notice that the bud is much smaller than what the leaf will become. How can something so tightly packed expand in both length and width as it grows? It comes down to the folding techniques that is used. This origami is known as Ha-ori (meaning 'leaf-fold'). It can unfold with just one pull and even though it does not fold up as easily, it makes a good attempt. This is a good example of bistability. The leaf folding pattern was discovered by Biruta Kresling. She learned how to paper fold from Koryo Miura, a Japanese expert in folding structures.
    Miura was not only an expert in folding structures but he was also a Japanese space scientist. His ideas of folding influenced his work in space science. Miura saw a crumpling pattern when you crumble a piece of paper, the paper was now in three dimensions. By 1978, Miura had a general theory of how to collapse a piece of paper. He wanted to apply it to folding solar pannels. He initially described his technique as a 'Developable Double Corrugation Surface' but also became known as Miura-ori.

    Miura-ori helped develop solar panel arrays for space satellites. Solar panels need as much surface area as possible to increase the energy produced. But to be launched into space they need to be a lot smaller. In Miura's space arrays, the panels have the same shape and angles as the paper-folds but since there is no one in space to pull the panels they needed joints and tension strut to manipulate them. Such an array went into space on March 18, 1995.

Below is a video on how to do a Miura-ori fold

Insects Can't Fly

"The fundamental laws of aero-
nautics, dynamics, and what ever
must soon convince the unbeliever
that bees were built to such a model,
they scarcely could do more than waddle.

The ratio of their body weight
to wing-span, he could demonstrate,
prelude takeoff, much less flight."
Sheenagh Pugh, 'Bumblebees and the Scientific Method'

    Flying insects are a miracle of robotics. They can turn left and right, go up and down, hover and avoid obstacles with ease with 'less computational power than a toaster', according to Rafal Zbikowski. Zbikowski is an engineer at Cranfield University working on flapping flight. For a long time, conventional theories of flight could not account for the amount of lift generated by insects. The equation used says that such creatures should not be able to fly. But in recent studies, biologists have began to unravel the complexity of insect flight and brought the science to the point where engineers can contemplate making flying vehicles that can flap their wings.
    In 1996, the US Defense Advanced Research Projects Agency (Darpa) initiated this research with $35 million to develop 'micro aerial vehicles (MAVs)'. The target was to create a flying object that could fit in a 15 cm sphere, weigh no more than 140 g, fly up to 2 hours and have a range of 10 km, operate in winds up to 50 kph, and be able to manoeuvre without a remote pilot. Zbikowski is working on a machine at the 15 cm limit while Ron Fearing is working on the much smaller scale of the blowfly.
    When you look at a wing of an airplane and how it works, it is much different than an insect. An airplane's wings move horizontal through the air to generate enough power to lift it. To do this, the upper surface off the wing is rounded and then flattens toward the rear, almost like a tear drop. The airflow has to split to pass over the wing which produces lift. If you imagine the air as visible particles then you can see the air particles as streamlines. The streamlines are symmetrical before it hits the wing but once the air hits the wings then they become asymmetrical. The streamlines are being pushed closer together. The only way to the air to move pass the wing without compression is to move faster than the air below the wing. Thus, the pressure above the wing is lower than the pressure below and the result is an upward pressure on the wing: lift, as shown above.
There are differences in the flight of an airplane and the flight of an insect. The main battle for a plane is gravity. For insects, gravity is less important. It is hard for engineers to design a machine to mimic the flight pattern of a fly because they use wheels, axles, ball bearing, and linkages while nature uses stretchy muscles and bendy hinges. It's challenging to find materials that can flex 200 times a second without breaking. It is also challenging to match their three basic movement (up and down, sweeping, and twisting).
    In 1996, Charlie Ellington had a breakthrough in his studies of insect flight. Using stereophotography, Ellington captured the flow of smoke around a tethered hawkmoth. He says he saw vortexes (whirls of air like miniature tornadoes) form along the front of the wing on the down stroke to create additional  lift. Ellington build a mechanical flapper about 10 times bigger than the hawkmoth to demonstrate his technique. This work was a great inspiration on the MAV movement but it had a lot of biomechanic skepticism.
    Ron Fearing began to work on an MAV and his version is known as the Micromechanical Flying Insect (MIF). The model is a blowfish which has a wingspan of 25 mm and flaps 150 times a second.

There is no attempt to copy the fly's exact appearance, he also is working making the machine out of sheets of carbon fibre to make it lighter than an actual fly.
    Scientists stress that a fly does not have to think about how to move it's wings, they just do it. Just like humans don't think about throwing an object, they just do it. A fly's sensory system is highly developed. They are able to process 150-200 pictures per second. This is an important aspect of how a fly can fly and this is why they are so hard to catch. The last thing that scientists need to apply to a robotic is this sensory system. They say that a sensory-rich feedback to control system will be the key to controlling MAVs.

The Gleam in Nature's Eye

"...first-beginnings have no colour,
But they do differ in shape, and from this cause
Arise effects of colour variation...
Hues change as light fall comes direct or slanting...
A peacock's tail, in the full blaze of light,
Change in colour as he moves and turns."
- Lucretius, De Rerum Natura


    Light became an evolutionary force over 500 million years ago in the Cambrian era. The eye is thought to have evolved on 40 separate occasions. But the eye also registers what it's looking at. What is there has only evolved because some other creatures can see it. For example, flowers evolved their colors to attract insects, and a peacock's tail evolved to attract females.
    Light is an important source of communication medium in both nature and technology. It has been used in nature for millions of years, but, it is only an emerging field in human technology. Optical technology is a promising area of study and the most anticipated product is the all-optical computer. Computers and their silicon chip microprocessors run on electrical impulses. We just need to know if it could be powered by light. The reason why this is such an anticipated product is that light can be pulsed 10 times faster than electricity and beams can cross each other without interfering. A problem with this is that light is very hard to control and it doesn't bend willingly. Eventually scientists were able to make a device that would make light bend and that is the photonic crystal. It works like the transistors in a silicon chip by only allowing light of certain wavelengths to pass through.
    The idea of the photonic crystal was proposed when the internet was being developed and they needed a vast increase in capacity of the telephone network. The first success of creating the photonic crystal was by Eli Yablonovitch in 199. His team spent four years drilling millions of 6 mm holes into solid blocks in a diamond like pattern. This material was later called Yablonovite. This started the long road to miniaturization.
    Butterflies and some marine creatures send optical messages by means of a nano scale photonic crystal. They have surface patterns with dimensions to the wavelength of various colors. The reason why the colors change when we shift our viewpoint is that the movement drastically changes the angle of rays of light from the reflecting surfaces. The most eye catching butterflies to show iridescence is the bright blue Morphos. Their wings are covered in scales that look like shingles on a roof top. The scales have ridges running down them. The intricate structure has a purpose; it controls how the light reflects off the scales. The Morpho's optical system evolved to show a strong blue from any angle. This pattern has been used commercially and is named after the butterfly: Morphotex fabric. It was created by the Teijin Corporation of Japan with collaboration with Nissan Motor Co. The Fabric has been used in the front seat covers of the Nissan Silvia Varietta Convertible. Below is a picture of the Morphotex fabric in comparison to the Morpho butterfly.

 
 

Clinging to the Ceiling

"Those rugged little bodies whose parts rise and fall in various inequalities,
Hills in the risings of their surface show,
As valleys in their hollow pits below."
- Richard Leigh, 'Greatness in Little'

Image of a gecko's foot

    Gecko's have an astonishing way of adhering to walls and ceilings with little to no effort exhorted. Something is holding it to the wall, but it is not it's muscles. For centuries, scientists have wondered how these animals can run up and down any kind of surface with no trouble. Geckos are a group of nocturnal lizards with about 850 species in all. They can be found all across the southern continents. The gecko that has the most research done on is the Tokay gecko (Gecko gecko), a large Asian species.
   The gecko began to appear in science in the mid-1990s because of Professor Bob Full's Polypedal Lab. He is an expert on animal locomotion meaning he belongs to the biomechanic wing in bio-inspiration. Much of his previous work was focused on insect motion but when he noticed the adhesive quality that gecko's have, he became interested right away. Full also involved Kellar Autumn in his work. Autumn studied geckos for most of his professional life. They wanted to find the exact principle at work that made the geckos feet adhesive and then apply it to a technical system. Autumn thought that the feet of a gecko was the most interesting. To the human eye, the pad of a geckos foot is crossed by transverse bands that look like reptile scales. It was not until the application of the electron microscope that they saw that the geckos foot had tiny bristles on the toes (about 500,000 on each foot). The ends of the bristles then fork out to between 100-1,000 mini-bristles. Just one gecko has about one billion of these points of contact. These bristles are the reason why the gecko can stick to anything. The bristles also don't need any muscle activation for them to stick, so a gecko can still stick to things when it's dead.

    Autumn's team found the force of a single gecko bristle to be 10 times more than you would have expected given the amount of bristles on the foot. If all of the bristles came in contact at one time on a surface then it would be able to support a 264 pound man. This is actually opposite to the Lotus-Effect because it created many contact points for a better adhesion. Ron Fearing also contributed to this work when he realized that it is not just the nervous systems of creatures that enable them to pull off incredible physical tasks, but most of the time it is the mechanics. Scientists immediately wanted to find ways in which this mechanism could be fabricated.
    They soon realized that creating a design for this would be difficult since human technology has not been able to create "bristle-like" products small enough to be compared to a gecko. The lab of Andre Geim used an atomic force microscope to create dimples in a wax surface to be used as a mold to make plastic pillars to mimic a gecko's bristle. The pillars were not exact comparisons but they were able to use it to create 'gecko tape'. The tape had limitations because the plastic was soft and after a few uses the pillars would stick together. The tape would also become very dirty after uses.
    Scientists then noticed that bristles needed to be compliant. They needed to have flexibility. Fearing notes that the soft sticky surface and the flexible backing is two levels of compliance. These ideas were compiled into the gecko mechanism and was patented by the Autumn/Full/Fearing team on May 18, 2004.
    For a long time people thought that there was something magical about the gecko. But it only comes down to the nanostructure of these animals that makes them so special. There are also many other animals that have this adhesive quality including beetles, flies, spiders and other lizards. It is also found that the larger the animal the more finer the bristles become.



Below is a video about Bio-inspiration to help you understand a little more about what it is:
3:50-7:08 goes into specific details about the gecko's foot with Bob Full and Ron Fearing.

 
   
 

Natures Nylon

"What Skill is the frame of Insects shown? How fine the Threads, in their small Textures spun?"        -Richard Leigh, 'Greatness in Little'

    Arachnophobia is the fear of spiders. Spiders haunt the mind of many people for many reasons. Maybe it is the eight eyes that scare people, or maybe it is the fear of the poison that spiders may have. In reality, there are only a few large, hairy poisonous spiders. Chapter 3 of The Gecko's Foot talks about the complexity of spider silk and how it could potentially be a good resource and the difficulty of producing this silk.
    The resilience of spider silk has long suggested the application of humans basically because it is so strong that it can capture an insect at speed without breaking. We sometimes think that spider silk is a delicate structure, which they are by themselves, but when combined together they can create a very strong material. For example, in Papua New Guinea, they have been draped across bamboo poles to make fishing nets. But producing a massive amount of spider silk to produce these kinds of materials is very difficult.
    The first spider silk exploit documented was in 1709 by a Frenchman named Xavier Saint-Hilaire Bon. He made gloves and stockings from the silk and presented them to King Louis XIV. In 1879 the Chinese Emperor made a gown made of entirely spider silk for Queen Victoria, and in the late 18th century, Austria had a tradition of painting on spider webs. There isn't a problem with spinning silk from a single spider but the problem is producing enough silk to make a useful product. It is estimated that you would need 27,468 female garden spiders to make 1 lb of spider silk. It is also nearly impossible to farm spiders because they are aggressive, solitary animals. This turned into the idea of creating a synthetic silk.
    In 1891, rayon (a silk like substance) was produced from cellulose, but the mimicking of natural silk on a commercial scale started with nylon in 1937. The structure of nylon is very different to the structure of natural silk but they have one thing in common and that is the amide group. The first serious product produced from nylon was Kevlar in 1963. But nylon and Kevlar are made with toxic chemicals and generate toxic waste. They are not biodegradable. With this situation, Nexia Biotechnologies in Quebec, Canada, claimed that they were able to produce an industrial amount of spider silk from genetically modified milk of goats. This silk was called BioSteel and it was developed under an Army contract to make flak jackets. BioSteel was very strong and useful for the Army. Nexia could not meet the Army's requirements for quality or quantity so the US Army withdrew from the industry. BioSteel has since then been downgraded because of its technical difficulties of producing bulk amounts. Below is a picture of nylon and Kevlar.
                                                                            Nylon

Kevlar

 

    The next approach to make a synthetic spider silk comes from David Knight. He founded Spinox, a company dedicated to producing technical silks. David focuses more on the spinneret on the spider to make the silk. A spiders spinneret produces a solid filament from the fluid silk inside of the spider. David made a spinner that can spin the liquid silk into a solid product. David's spinneret never made it to the industrial stage. In an interview with Knight and Forbes, Knight states that when spider silk is finally commercially produced, it wouldn't first go to the army first, but it would be used for biomedical applications such as fibers for closing wounds and other medical aids.
    The quest of producing a synthetic spider silk is ever going. It is proving to be a difficult process. This just shows the complexity of nature and how hard it is to mimic it's great creations. With bio-inspiration, it is becoming much easier to achieve.