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.
   
      

About the Author

                                                                    
                                                                      Peter Forbes

  Peter Forbes is a science writer. Forbes has a special interest in the relationship of science and art. At first, Peter trained to be a chemist and he also worked in pharmaceutical and natural history publishing. He also wrote articles for magazines like New Scientist and World Medicine. Other books written by Peter Forbes are Dazzled and Deceived: Mimicry and Camouflage, Abolishing the Dark, and The Aerial Noctiluca: Poems. Forbes is mostly known for his books.

To learn more about Peter Forbes, visit http://www.pforbes.org/ for more information.

The Great Sacred Lotus Cleans Up

"Though buried deep
In the slime of the pool,
Unstained and untouched
You came forth to the world
Glorious in beauty,
Pure and serene:

Yet in your innocence
Oft you deceive us
Transforming the dew
On your life-giving leaves
Into sparkling gems!"
Gonnoske Komai, 'To the Lotus-Bloom'

  Through-out human history, the lotus flower has been worshipped for many reasons. Their beauty makes it the symbol of the triumph of enlightenment over the dross of earthly life. This flower is such an influence in the Chinese, Indian, and Japanese culture that the name is a byword for 'purity'. In these different cultures, you can find poems describing the lotus and how it unfolds its leaves from dirt and muck, being completely clean. If you did not know, the lotus flower typically thrives in shallow ponds, lagoons, and marshes making it rare to see bright colored flowers in a mucky environment. With one look at this flower you would wonder how such beauty evolved to grow in a dirty place. It's almost like magic, if you were to drop a single droplet of water onto a lotus leaf, it would easily fall off the leaf with ease. A comparesson to this would be like dropping mercury on a table. This would potentially become known as the Lotus-Effect.
   The discoverer of the Lotus-Effect was Professor Wilhelm Barthlott, the director of the Nees-Institute of Bio-diversity at Bonn, Germany. After the scanning electron microscope (SEM) was invented, Barthlott was able to view the surface of flowers in fine detail. But to be able to study something under the SEM microscope, the specimen needed to be cleaned because contaminants could ruin a picture. Barthlott started to realize that the specimen's that did not need to be cleaned before viewing it had the roughest surfaces. When a surface of a flower has a lot of little and tiny bumps, it forms to become a water-repellent substance. In other words, the water sits on top of the tiny bumps as shown in the diagram to the right.

These bumps make it difficult for dirt to adhere to the surface so when water passes over the dirt it takes the dirt with it. The bumps also make it so water rolls off the surface at a low contact angle. Flowers that had the roughest surface were always 'clean-looking'. Barthlott's discovery became the most noticeable in the lotus flower, calling this effect the 'Lotus-Effect'.
   Barthlott knew that his discovery could potentially be used in commercial products. His next step was to create a technical demonstration of the self-cleaning effect and so he then created the 'honey-spoon'. Barthlott made a homemade spoon with his micro-rough silicone surface. When the spoon was placed into a honey jar, the honey fell off the spoon with ease. In 1994, this simple demonstration helped him apply for a patent.
   In 1998, the Lotus-Effect teamed with Ispo's paint to create an exterior building paint called Lotusan. It comes with a 5-year no cleaning guaranteed and has been very successful in the German industry. This product is the only bio-inspired product to have made serious profits.