Monday, April 1, 2013

Biomimicry: From Termites to Towers

Almost everyone on the planet has had their life improved by biomimicry, “the design of production of materials, structures, and systems that are modeled on biological entities and processes.” (Oxford Dictionary). Another way of describing biomimicry would be technology by man inspired by nature. There's good reason to look toward biomimicry; billions of years of evolution have lead to many examples of complex diversity in nature. Many sustainable technologies & products have been created because of people examining nature's existing efficiency, with a broad range that includes passive cooling technology inspired by termites, whale powered wind turbines, gecko infused tape and, most easily recognizable due to it's many uses and longevity, Velcro.

Velcro was designed in 1941 & patented in 1955 by Swiss electrical engineer & hunting enthusiast George de Mestal (Hall of fame inventor Profile). De Mestral's imagination was sparked by returning home from a hunting trip one day & examining the recently plucked burrs that stuck to his jacket & his dogs fur (Gregory). Burrs, which are generally attached to a seed or dry fruit, have hooks as both a means to protect the plant from herbivores & also as a means of seed dispersal. De Mestral took some of the burs and examined them under a microscope. What he saw was hook-like seeds meshed with hooped fibers gripping and fastening to each other. De Mestral considered that the adhesive qualities of plants with burrs could be useful when applied to everyday life, an example of biomimicry in action.

It's somewhat ironic that de Mestral was inspired by a part of a plant in nature that was, until that point, only an annoyance for humans. It turns out the inventor was also as tenacious as the burrs themselves; his idea did not win over investors after it's inception. Another ironic spot in the life of de Mestral considering he received his first patent at the age of 12 only to be “severely” & “openly laughed at” (Thomas) when he initially pitches his greatest idea yet. 
After three years of work de Mestral finally had his initial design completed: two lineal cotton fabric strips, or round squares, sewn or adhered to opposite sides. The first fabric strip had 300 hooks per square inch and the second fabric strip had 300 loops per square inch (Thomas). The initial design worked by not as effectively due to being made of cotton. 
Cotton is a fluffy fiber that grows around seeds of a shrub plant from a genus called Gossypium. The fiber is around 90% cellulose which is a polysaccharide (long string of carbohydrate molecules joined together) comprised mostly of glucose. Cotton is spun into a yarn and is then turned into a flatter material. After this refinement the cotton is still fluffy and proved to be a poor material to create what would become Velcro. Eventually de Mestral discovered that he could create the texture needed by sewing nylon under an ultra violet light, causing the material to be both burned & sewn into the shape (Strauss). After a couple years of production de Mestral was producing over sixty million yards of Velcro per year. Today it's an everyday item capable of supporting 175 pounds per two square inches (Freeman) & is used in items ranging from pen holders to automobiles. 
Aristotle has one of the earliest recorded comments about biomimicry, commenting on how the Gecko can “run up and down a tree in any way.” (Aristotle) One wonders what the philosopher would think of modern times: recently a product has become available that harnesses the gripping power of a Gecko's setae (small hair-life structures on the foot of a Gecko) called Gecko Tape. Gecko Tape is made with synthetic setea that emulates a Gecko's setae. It was developed between a collaboration of the Manchester Center for Mesoscience and Nanotechnology and the Institute for Microelectronics Technology in Russia in 2001 after two year’s of research (Nature). The research yielded a product that is powerful but still not as strong as the feet of a Gecko. It turns out that little reptilian feet are complex.

A gecko's foot has toe pads consisting of about a half million setae made of keratine (a fibrous structural protein) and each one of these has fine hairs with hundreds of small projections called “spatulae” on a nanoscale at their ends (Nature). Robert Full from the University of California was the first to discover that the adhesion from Gecko feet was due to Van der Waals forces created between the spatulae and the surface. Van der Waals forces are “intermolecular forces created by induced polarization of molecules” which “become significant on the micro and nanoscale.” (Nature) But the mighty foot of the Gecko continues to hold mysteries: Andre Grim, credited with being the father of synthesized setae, found that capillary forces also aided with the Gecko's adhesive ability. Capillary forces are “attractive forces created by the surface tension of a molecular layer of absorbed water that forms between two surfaces” (Nature). This lead to the development of nanotubes of synthetic Gecko foot hair, which when applied to the old synthetic satae formula creates a formula that could be potentially stronger than the properties of a regular Gecko foot. At the moment each hair has “the same adhesive force as a single gecko setae.” (Shah).

Design cues from mother nature don't just manifest as accidental inspiration for alternatives to zippers or a better sticking roll of tape. Biomimicry has also been used by architects to create more efficient sources of energy.

WhalePower produces giant blades for wind turbines as an alternate form of energy. Already commercially available, WhalePower has an advantage over other wind turbine designs; it's modeled after the “fluid dynamics and biomechanics” (The Science | Whalepower) of a humpback whale flippers. 
Nature has given the humpback whale a very efficient flipper. They provide lift and reduce drag, channeling flow and increasing aerodynamic efficiency due to tubercles (a round node in the bone or skin). When tubercles are in human lungs we call this tuberculosis, however when they are on the edge of humpback whale flippers they are called innovative. By replicating the texture of the tubercles on humpback whale flippers designers for WhalePower were able to craft a more efficient wind turbine. Wind tunnel tests have shown that models of blades designed with humpback whale tubercles, instead of smooth surface blades, offer full dynamic improvements including a “32% reduction in drag, 8% improvement in lift, and a 40% increase in angle of attack of smooth flippers before stalling.” (Fish) WhalePower is extending this technology to hydroelectric turbines, irrigation pumps & ventilation fans.

In Harare, Zimbabwe, architects have looked toward termites as a way to discover new building techniques. Termite mounds in Africa can rise to heights of over thirty feet. To compare to a man made structure that would be equal to a human erecting a building 2,743 feet high (Steinu). These mounds have complex systems such as ventilation tubes and tunnels that continue up to 200 feet underground. When comparing this to human structures the termite structures are much larger. The architects on the Eastgate Centre building in Harare know this, that's why they are developing their high-rise buildings with a design modeled after termite ventilation systems to maintain a consistent temperature in their structures. These buildings, designed under biomimicry principles, use no conventional air-conditioning or heating yet stays regulated “year round with dramatically less energy consumption using designed methods inspired by indigenous Zimbabwean masonry and the self-cooling mounds of African Termites” (Fahrenbacher). 
Termites in Zimbabwe feed on a specific type of fungus that must be regulated at exactly 87 degrees Fahrenheit. This is quite the job for the small termites as temperatures outside range from 35 degrees to 104 degrees (Fahrenbacher). The termites regulate the mound by opening and closing a series of heating and cooling vents. By digging new vents and plugging old ones the termites are able to keep the fungus at its appropriate temperature & enjoy a constant source of food.

The ventilation system designed by termites is essential to the Eastgate Centre high-rise tower design. Outside air is warmed or cooled by the building mass itself which is determined by checking the temperature of the concrete and the air. Air is continually drawing in by large open spaces and fans on the first floor. Fresh air replaces stale air and exits through ports in the ceiling of each floor. By doing this structures end up using 10% less energy of conventional buildings of its size, which has trickled directly to residents; rent is up to 20% lower than the surrounding buildings of Eastgate Centre. 
Humans have a tendency to take things in nature and give it a human element. Many times this makes something more accessible for the better of humanity. For example, taking many randomly shaped stones and refining it into a protective structure in a shape of a square. Biomimicry is placed in a reversed but also welcoming context: it's technology for us all, inspired by nature, to make objects with a human element more efficient for humans. Biomimicry will continue to improve the work of architects, scientists, designers, artists and the rest of the world.


Works Cited

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Gregory, Josh. From Thistle Burrs to... Velcro(21st Century Skills Innovation Library: Innovations from Nature). North Mankato: Cherry Lake Publishing, 2012. Print.

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Shah, Gaurav. "Modeling of Gecko-Feet Hairs for Artificially Fabricated Dry Adhesives." 23 Feb. 2004. Carnegie Mellon. 6 Dec. 2005

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