Do they not see the birds suspended in mid-air up in the sky? Nothing holds them there except the almighty.There are certainly signs in that for people who believe (Quran 16:79)
And in your creation and in what He spreads abroad of animals there are signs for a people that are sure. (Quran 45:4)
And in the earth are tracts (diverse though) neighboring, and gardens of vines and fields sown with corn, and palm trees – growing out of single roots or otherwise: watered with the same water, yet some of them we make more excellent than others to eat. Behold, verily in these things there are signs for those who understand (Quran 13:4)
Biomimetics is a new science where idea and inspiration are taken from nature to solve human problems, add values or to create new products. In textile, biomimetics has a long history with precious, secretive silk for more than two thousand years. Trying to mimic natural fiber created synthetic revolution and a number of exciting synthetic fibers have come out in the process. Acrylic, nylon, viscose and many others are result of that mimicking nature. Today the range goes beyond fiber: it can be found to produce camouflage military ranges, swim suit, smart fabric, self cleaning textile, velcro, to give few examples. This paper reviews the products and technology that are already available in the market and the future prospect that could change the way of engineering textile.
What is Biomimetics?
Biomimetics (Greek bios = life and mimesis = imitation) is the science and arts to solve human problems as it is called ‘design inspired by nature’. The core idea is that nature, imaginative by necessity, has already solved many of the problems that we are facing. Biomimetics is also known as bionics (in 1960 by US Airforce), biomimesis, biomimicry, biognosis, biologically inspired design etc.
Biomimetics is relatively a new term for a process as old as human kind. Perhaps, we all more or less wanted to be mythical Icarus in our early childhood, who failed to flee away with artificial wings (fig 1), ‘Daedalus wings’ named after his father due to design failure as material was melted upon sun’s heat. Today, biomimetics has been inspiring in every aspects of engineering, ‘We have had the Stone Age, the Bronze Age, and the plastic age…. The future is the designed material age.”
- Aeroplane was result of flying technique of birds. Leonardo Da Vinci sketched birds flying technique as early as 16th century while Wright brothers, first successful aviators, modeled their planes’ wings according the birds.
- Design and function of fins, which divers use, was copied from the legs of water creatures like seals.
- Fastest train in the world, the Japanese Shinkansen Bullet Train, created too much noise when it emerges from a tunnel. Seeing how kingfisher dives to catch fish with little splash; the train engineers modeled the front-end of the train after its beak (fig 2). The result is astonishing: a quieter train, with 15% less use of electricity and 10% faster speed .
- Warning for Tsunamy war has been mimicked from extra sensory communication of dolphins which can sense at the very early stages.
Gecko tape is the new invention by Prof A. K. Geim of University of Manchester, a glue-free, yet sticky, just like gecko. Geckos have amazing ability to move through all types of surfaces, vertically or horizontally at ease, which is due to the presence of billions of tiny fibers, ‘setae’ on their feet (fig 3). These tiny fibers create Van Der Walls force with the surface, a weak force but billions of fibers make enough force to stick on the surface. No wonder we would see spider kids hang on the wall very soon.
History of synthetic fiber development is history of Biomimetics
Natural fiber such as cotton, wool, linen and Silk has varieties of inherent properties in terms of comfort, moisture absorption, touch, warmth etc. On the other hand, these fibers have their limitation too. Cotton and linen wrinkled from wear and washings. Silk required delicate handling. Wool shrank, was irritating to the touch, and was eaten by moths. As a result development of synthetic fiber was fast paced to match the supply and demand.
Silk has attracted the scientists most in that respect. Silk is obsessively protected by the Chinese for more than two thousand years. It was reserved for only the royal dignitaries, rulers, emperors, and for the richest. The famous trade route ‘Silk Road’ was in operation in the second century BC connecting East, South, and Western Asia with the Mediterranean world, as well as North and Northeast Africa and Europe . Chinese tried to make artificial silk some 3000 years ago  but The earliest published record of an attempt to create an artificial fiber took place in 1664. English naturalist Robert Hooke suggested the possibility of producing a fiber that would be ‘if not fully as good, nay better’ than silk. His goal remained unachieved for more than two centuries. In 1855, a Swiss chemist, Georges Audemars invented the first crude artificial silk but productivity is very low. However, this has created a momentum for making of synthetic fiber. In 1884, a cellulose based artificial silk was patented by French chemist, Hilaire de Charbonnet,and his fabrics of ‘artificial silk’ (fig 4) caused a sensation at the Paris Exhibition in 1889 . He was considered as the father of the rayon industry and set up a commercial rayon plant; nevertheless, due to its flammability, it was removed from market. The first safe and practical production method to produce artificial silk was patented in 1894, by British inventors, Charles Cross, Edward Bevan, and Clayton Beadle, that came to be known as ‘viscose’ and finally rayon in 1924. Several attempts to produce “artificial silk” in the United States were made during the early 1900’s but none were commercially successful until the American Viscose Company, formed by Samuel Courtaulds and Co., Ltd., began production its production of rayon in 1910 .
Then nylon appeared about a half century later around 1939 by Dupont, which aimed to mimic silk chemically, and has similar amide groups. Nylon fibers were long, smooth and offer silk like handles but stronger. Then silk like ultra fine fibers were produced by copying the operating system of silk worm. On the other hand, acrylic was developed as ‘artificial wool,’ in 1944 by Dupont and commercial production started in 1950. Acrylic is warm, a very similar to wool and very cheap alternative for woolen clothing and carpet. Modern highly functional fibers those are produced by biomimetic approach are listed in Table 1:
Table 1 High function fibers developed using biomimetic approach 
|Discovery/invention||Structures mimicked||Advanced-function fibers||Discoverer/inventor|
|Lumen structure of cotton||Hollow fiber||Du Pont|
|Conjugate structure of wool||Elucidation of crimp structure Crimpled fiber||M. Horio (Kyoto University)|
|1964||Silver trappings of leather||Artificial leather||O. Fukushima (Kuraray)|
|1965||Super-fine structure of leather||Micro-denier fiber Artificial suede||M. Okamoto (Toray)|
|1978||Micro-crater structure of cornea of moth||Fiber with deep colors and luster||S. Yamaguchi (Kuraray)|
|1979||Supramolecular structure of enzyme||Odor-killing fiber||H. Shirai (Shinshu Univ.)|
|1980||Triangular cross-section of silk||Shingosen with silk scrooping||Y. Sato (Toray)|
|1980||Capillary water absorption by
|Water absorption porous hollow fiber||T. Suzuki (Teijin)|
|1983||Surface structure of lotus leaf||Water-repellent fabric||F. Shibata (Teijin)|
|1989||Multi-layered structure||Fiber with light interference function||K. Matsumoto (Kyoto Institute of Technology)|
Modern Biomimetic Examples in Textile
Camouflage fabric is itself has a history in wars, as early as 1750s to 1800s, followed by the British use of Khaki after 1850 in India. But camouflage, as from French word ‘camoufler’ (to disguise) was first introduced in First World War by French. The idea was concealment of people and objects, to hide in plain sight, as like the animals like deer, butterflies or moths (fig 5). Textiles are widely used as the camouflage medium, in the form of light flexible nets, covers, accessories and clothing items . Camouflage is now applied to UV, near infrared region, or visual decoys, to give some examples.
SELF CLEANING TEXTILE
Lotus leaves have natural cleaning mechanism due to its surface morphology. Lotus leaf consists of waxy surface with many tiny micron (10-6m) size papillae, which in turn covered with hair like tubes made of wax crystals around 1nm (10-9 m) in diameter(Fig 6). The combination of these micro and nano scale structural attributes greatly reduces the contact are between the surface and water molecules.
Similarly, this self cleansing also found naturally in the wings of butterflies and dragonflies (fig 7). The surface is hydrophobic in nature and has a rough surface under microscopic observation. This nanoscpoic rough surface repels water and effectively cleans dirt during the rainfall compare to the smooth hydrophobic surface (fig 8). This self cleaning technology has been considered as one of the best inventions by Time magazine in 2006.
Nano-tex™ (www.nano-tex.com) was the first brand in 2000 that applied this principle at molecular level using nanotechnology to produce soil repellent fabric for apparels and home textile (fig 9). According to them the fabric resists spills, repels stains, wicks away moisture and resist statics without sacrificing comfort. Designer brands like Hugo Boss, René Lezard, Paul Stuart and big brand like Nike, Adidas, and Gap are all using Nano-tex™ in their fashion line. BASF has developed water repellent finish Mincor™ which uses nanoparticles and water resistant polymers such as polyethylene, polypropylene and wax that is applied by spraying. These polymers self assemble into tiny structures that can mimic the lotus effect.
Velcro, a revolutionary fabric may be the most well-known biomimetic invention in textile. In 1948, Swiss engineer George de Mestal during hiking accidentally discovered that some seeds from cockleburr (fig 10 a, b) were plucked in his pants and in dog’s coat. He found that their spines were tipped with tiny hooks that stick out from the seeds and provide a hook-and-loop construction, which grips instantly, but can be ungrip with a light force (fig 10c). This led to the invention of ‘Velcro’, a combination of the word velour and crochets , an alternative to the zipper. The commercial design was patented by him in 1955 and set up a production site to manufacture sixty million yards of Velcro per year.
STRUCTURAL COLORED FABRIC
The well known method for textile industry for coloration is through dyeing and/or printing by using dye and pigment. However, in nature case if we look into the butterfly (fig 11), they are more colorful that we can produce. It is more interesting to know that the coloration of butterfly wings doesn’t only come from pigmentation, but also from the structure of the wing scales, which is called as structural color. Pigments found in butterflies (melanins etc.) can produce only yellow, orange-yellow, red, black, and brown colors. Green, blue and violet color comes from layers of nanoparticles separated by layers of air . This nanolayer is in a pattern of mosaic tiles, where each tile of pattern has different structural features as well as tiny gap among them for light refraction . The thickness of the layers changes the color we see.
Morpho rhetenor butterfly inhabits along the amazon in South Africa and called ‘living jewels.’ Their colors are not only vibrant but there is no problem of fastness i.e. the color doesn’t wear out. This way of producing color is very fascinating as no dyeing and finishing will take place, which means no toxic chemicals, waste water and would consume less energy and resources to produce.
Teijin Fibers Limited of Japan produces a new monofilament named Morphotex®, a first optical coloring fiber (fig 12), that mimics morpho butterfly wings, by using interference to produce color without pigments or dyes . The fabric is produced from 61 layers of polyester or nylon in alternative way, with 70nm thickness, and laminated. Four types of basic colors such as red, green, blue and violet are allowed to be developed by precisely controlling the layer thickness according to visible wavelength. Teijin claimed that Morphotex has wide applications, e. g. filament, short-cut fiber and powdery materials  and could be a renewable source for solar textile.
SHARK SKIN FABRIC FOR HIGH PERFORMANCE SWIMSUIT
We have seen the superhuman performance of American swimmer Michael Phelps at Beijing Olympic 2009, winning a record-breaking eight gold medals in the swimming pool to become the greatest ever Olympian. This record breaking endeavor was due to Speedo’s third generation swimsuit, Fastskin LZR Racer® speed suit (fig 13), developed with the help of NASA. The suite is constructed from Speedo’s unique LZR pulse fabric, which is ultra lightweight, strong, water repellent, and fast drying and woven from chlorine resistant elastane and ultra fine nylon yarn.
Speedo’s swimsuit first appeared in 2000 Sydney Olympic as a winner after four years of research and development with Natural History Museum. This swimsuit used Shark skin fabric, which mimics shark’s excellent drag reduction properties . Surface of shark skin is covered in tiny ‘teeth’ or dermal denticles and their shape and positioning varies across the shark’s body, managing the flow of water in the most efficient way (Fig 14).
SMART FABRIC WITH BETTER MOISTURE MANAGEMENT
Moisture management becomes increasingly important in sportswear segment, particularly for activewear. A textile prototype system was developed based on the opening and closing mechanism of a pine cone (fig 15), which opens when closes when its damp and again open up when it is dry.
Nike introduced similar concept to produce its Macro React range with a fish-scale pattern, first worn by tennis star Maria Sharapova at US Open 2006 and later by Roger Federer at Wimbledon (fig 16). When someone wear this clothing, upon perspiration, the flaps in the fabric swings open to release heat and moisture to keep one dry and cool. The same clothing is made way for golf dresses .
On the other hand, Azko Nobel is marketing ‘Stomatex’ brand, which they claimed ‘the most comfortable clothing and footwear systems in the world today.’ The clothing is made of neoprene fabric along with foam insulation which has tiny hole like dome (fig 18), as like the transpiration process within a leaf, which provides a controlled release of water vapour to make the clothing comfortable. Well at the rate of global warming, it won’t be any surprise if we see it at more domestic uses.
This is going to be exciting new world of inventions by following nature, and textiles are in the forefront. As a matter of fact multidisciplinary collaboration of research-with biological, chemical, physical, and engineering is required to take the textile field into new horizon. Some of the new prospect could be 
- Nature uses only two polymers protein and polysaccharide to produce such a variety and versatility yet synthetic world uses more than 300 polymers, and metals, to produce materials with few variations 
- Cellulose, a raw materials of many fibers, is produced with CO2 and water by photosynthesis, with complex multilayer structure, even though nature has very low, 0.3% of CO2. Most of the synthetic fiber needs many raw materials and homogeneous.
- Even though silk has been tried many ways, yet, not all of the silk’s attributes were reconstructed. For example, the characteristics of luster, moisture absorbency, and bright dyeability of silk have not yet been achieved.
- The synthetic industry produces fiber by extrusion through fixed nozzle of spinneret; however, silkworm produces silk by drawing by moving its nozzle (mouth) with no spinneret. Silkworm fixes its fibroin protein at the one end to the ground, and swings it head in the manner of a number ‘8’ to draw fibroin.
- Human hair or wool grows simultaneously as it polymerized from amino acids. Since both of them spun immediate after polymerization so there is no entanglement. If the hair growing mechanism can be mimicked then wool can be produced artificially.
Nanotechnology and biotechnology would be the key to unlock the potential for biomimicking textiles in future.
Look deep into nature, and then you will understand everything better ~Albert Einstein
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