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.