Biomimicry

airfoil

George de Mestral

Biomimicry [bahy-oh-mim-ik-ree] is the imitation of biological systems in human technology. Living organisms have evolved well-adapted structures and materials over geological time through natural selection. Nature has solved engineering problems such as self-healing, environmental exposure tolerance, hydrophobicity (waterproofing), self-assembly, and harnessing solar energy.

One of the early examples of biomimicry was the study of birds to enable human flight. Although never successful in creating a ‘flying machine,’ Leonardo da Vinci (1452–1519) was a keen observer of the anatomy and flight of birds, and made numerous notes and sketches on his observations as well as designs of rudimentary ornithopters based on bats. The Wright Brothers, who succeeded in flying the first heavier-than-air aircraft in 1903, derived inspiration from observations of pigeons in flight. Their airfoil was based on a design by German ‘Glider King’ Otto Lilienthal who published ‘Birdflight as the Basis of Aviation.’ Velcro, another famous example, was inspired by the tiny hooks found on the surface of burs.

The term ‘biomimetics’ was coined by the American biophysicist and polymath Otto Schmitt during the 1950s. It was during his doctoral research that he developed the Schmitt trigger (a device that modulates electric signals) by studying the nerves in squid, attempting to engineer a device that replicated the biological system of nerve propagation. He continued to focus on devices that mimic natural systems and by 1957 he had perceived a converse to the standard view of biophysics at that time, a view he would come to call biomimetics. Schmitt wrote in his autobiography that ‘Biophysics is not so much a subject matter as it is a point of view. It is an approach to problems of biological science utilizing the theory and technology of the physical sciences. Conversely, biophysics is also a biologist’s approach to problems of physical science and engineering, although this aspect has largely been neglected.’ A similar term, ‘Bionics’ was coined by military doctor Jack Steele in 1960 at Wright-Patterson Air Force Base in Dayton, Ohio where Otto Schmitt also worked. Steele defined bionics as ‘the science of systems which have some function copied from nature, or which represent characteristics of natural systems or their analogues.’ During a later meeting in 1963 Schmitt stated, ‘Let us consider what bionics has come to mean operationally and what it or some word like it (I prefer biomimetics) ought to mean in order to make good use of the technical skills of scientists specializing, or rather, I should say, despecializing into this area of research.’

In 1969 the term ‘biomimetics’ was used by Schmitt to title one of his papers, and by 1974 it had found its way into Webster’s Dictionary, ‘bionics’ entered the same dictionary earlier in 1960 as ‘a science concerned with the application of data about the functioning of biological systems to the solution of engineering problems.’ ‘Bionic’ took on a different connotation when author Martin Caidin referenced Jack Steele and his work in the novel ‘Cyborg’ which later resulted in the 1974 television series ‘The Six Million Dollar Man’ and its spin-off, ‘The Bionic Woman.’ The term bionic then became associated with ‘the use of electronically operated artificial body parts’ and ‘having ordinary human powers increased by or as if by the aid of such devices.’ Because the term bionic took on the implication of supernatural strength, the scientific community in English speaking countries largely abandoned it. The term ‘biomimicry’ appeared as early as 1982. It was popularized by scientist and author Janine Benyus in her 1997 book ‘Biomimicry: Innovation Inspired by Nature.’ The term is defined in the book as a ‘new science that studies nature’s models and then imitates or takes inspiration from these designs and processes to solve human problems.’ Benyus suggests looking to nature as a ‘Model, Measure, and Mentor’ and emphasizes sustainability as an objective of biomimicry.

Mimicking the diving behavior of animals, researchers have recently discovered that humans have a similar capacity to lower brain temperature and suppress metabolism for neuroprotection. This has now opened a real possibility of devising means for humans to sustain this state, not unlike the elusive and enigmatic feat of animal hibernation, e.g., lemurs (primates) and bears. This would have profound biomedical implications for healthcare and for treating an unmatched range and diversity of serious life-threatening clinical conditions, and in a fully personalized way, things like stroke, blood-loss, burns, cancer, chronic obesity, epileptic seizures, etc. An experimental trial, recently conducted in Sweden seemingly resulted in a sustainable variant of this state in a human breath-hold diver.

A virus is a nonliving particle ranging from the size of 20 to 300 nm capsules containing genetic material used to infect its host. The outer layer of viruses are remarkably robust and capable of withstanding temperatures as high as 60 °C and stay stable in a wide range of pH range of 2-10. Viral capsids can be used to create several nano device components such as nanowires, nanotubes, and quantum dots. Tubular virus particles such as the tobacco mosaic virus (TMV) can be used as templates to create nanofibers and nanotubes since both the inner and outer layers of the virus are charged surfaces and can induce nucleation of crystal growth. This was demonstrated though the production of platinum and gold nanotubes using TMV as a template.

Morpho butterfly wings contain microstructures that create its coloring effect through structural coloration rather than pigmentation. Incident light waves are reflected at specific wavelengths to create vibrant colors due to multilayer interference, diffraction, thin film interference, and scattering properties. The scales of these butterflies consist of microstructures such as ridges, cross-ribs, ridge-lamellae, and microribs that have been shown to be responsible for coloration. The same principles behind the coloration of soap bubbles apply to butterfly wings. The color of butterfly wings is due to multiple instances of constructive interference from structures such as this. The photonic microstructure of butterfly wings can be replicated through biomorphic mineralization, a nanotech process that mimics the way living organisms produce minerals (e.g. when a mollusk secretes its shell). A display technology based on the reflective properties of certain morpho butterflies was commercialized by Qualcomm in 2007. The technology uses Interferometric Modulation to reflect light so only the desired color is visible in each individual pixel of the display.

Researchers studied the termite’s ability to maintain virtually constant temperature and humidity in their termite mounds in Africa despite outside temperatures that vary from 1.5 °C to 40 °C (35 °F to 104 °F). They initially scanned a termite mound and created 3-D images of the mound structure, which revealed construction that can influence human building design. The Eastgate Centre, a mid-rise office complex in Harare, Zimbabwe that was developed based on termite mound research stays cool without air conditioning and uses only 10% of the energy of a conventional building its size. Janine Benyus refers in her books to spiders that create web silk as strong as the Kevlar used in bulletproof vests. Engineers could use such a material—if it had a long enough rate of decay—for parachute lines, suspension bridge cables, artificial ligaments for medicine, and other purposes. Other research has proposed adhesive glue from mussels, solar cells made like leaves, fabric that emulates shark skin, harvesting water from fog like a beetle, and more.

Biomimicry may also provide design methodologies and techniques to optimize engineering products and systems. An example is the re-derivation of Murray’s law, which in conventional form determined the optimum diameter of blood vessels, to provide simple equations for the pipe or tube diameter which gives a minimum mass engineering system. The Bombardier beetle’s powerful repellent spray inspired a Swedish company to develop a ‘micro mist’ spray technology, which is claimed to have a low carbon impact (compared to aerosol sprays). The beetle mixes chemicals and releases its spray via a steerable nozzle at the end of its abdomen, stinging and confusing the victim. Holistic planned grazing, using fencing and/or herders, seeks to restore grasslands by carefully planning movements of large herds of livestock to mimic the vast herds found in nature where grazing animals are kept concentrated by pack predators and must move on after eating, trampling, and manuring an area, returning only after it has fully recovered.

Proposed research includes climbing robots, boots, and tape mimicking geckos feet and their ability for adhesive reversal; treads on tires inspired by the toe pads of tree frogs; self-sharpening teeth found on many animals, copied to make better cutting tools; protein folding used to control material formation for self-assembled functional nanostructures; better ceramics by copying the properties of seashells; polar bear fur inspired thermal collectors and clothing; mimicking the arrangement of leaves on a plant for better solar power collection; studying the light refractive properties of the moth’s eye to produce less reflective solar panels; and self-healing materials, polymers and composite materials capable of mending cracks.

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