Biomimetics or biomimicry is the imitation of the models, systems, and elements of nature for the purpose of solving complex human problems.[1] The terms "biomimetics" and "biomimicry" derive from Ancient Greek: βίος (bios), life, and μίμησις (mīmēsis), imitation, from μιμεῖσθαι (mīmeisthai), to imitate, from μῖμος (mimos), actor. A closely related field is bionics.
Living organisms have evolved well-adapted structures and materials over geological time through natural selection. Biomimetics has given rise to new technologies inspired by biological solutions at macro and nanoscales. Humans have looked at nature for answers to problems throughout our existence. Nature has solved engineering problems such as self-healing abilities, environmental exposure tolerance and resistance, hydrophobicity, self-assembly, and harnessing solar energy.
History
One of the early examples of would-be 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 sketches of "flying machines".[3] The Wright Brothers, who succeeded in flying the first heavier-than-air aircraft in 1903, allegedly derived inspiration from observations of pigeons in flight.[4]During the 1950s the American biophysicist and polymath Otto Schmitt developed the concept of "biomimetics".[5] During his doctoral research he developed the Schmitt trigger by studying the nerves in squid, attempting to engineer a device that replicated the biological system of nerve propagation.[6][need quotation to verify] 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.[5]
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.In 1960 Jack E. Steele coined a similar term, bionics, 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".[2][7] During a later meeting in 1963 Schmitt stated,
— Otto Herbert Schmitt, In Appreciation, A Lifetime of Connections: Otto Herbert Schmitt, 1913 - 1998
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 researchIn 1969 Schmitt used the term “biomimetic“ in the title one of his papers,[8] 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 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-offs. 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".[9] Because the term bionic took on the implication of supernatural strength, the scientific community in English speaking countries largely abandoned it.[10]
— Otto Herbert Schmitt, In Appreciation, A Lifetime of Connections: Otto Herbert Schmitt, 1913 - 1998
The term biomimicry appeared as early as 1982.[11] Biomimicry was popularized by scientist and author Janine Benyus in her 1997 book Biomimicry: Innovation Inspired by Nature. Biomimicry 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.[12]
Commercial applications
Fabrication
Scanning electron micrograph of rod shaped tobacco mosaic virus particles
Biomorphic mineralization is a technique that produces materials with morphologies and structures resembling those of natural living organisms by using bio-structures as templates for mineralization. Compared to other methods of material production, biomorphic mineralization is facile, environmentally benign and economic.[13]
Display technology
Vibrant blue color of Morpho butterfly due to structural coloration
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.[14] 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 structural color has been simply explained as the interference due to alternating layers of cuticle and air using a model of multilayer interference. 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 to yield similar properties. The photonic microstructures can be replicated using metal oxides or metal alkoxides such as titanium sulfate (TiSO4), zirconium oxide (ZrO2), and aluminium oxide (Al2O3). An alternative method of vapor-phase oxidation of SiH4 on the template surface was found to preserve delicate structural features of the microstructure.[15] A display technology ("Mirasol") based on the reflective properties of Morpho butterfly wings 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.[16]
Possible future applications
Leonardo da Vinci's design for a flying machine with wings based closely upon the structure of bat wings
Biomimetics could in principle be applied in many fields. Because of the complexity of biological systems, the number of features that might be imitated is large. Biomimetic applications are at various stages of development from technologies that might become commercially usable to prototypes.[17]
Prototypes
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). Researchers initially scanned a termite mound and created 3-D images of the mound structure, which revealed construction that could influence human building design. The Eastgate Centre, a mid-rise office complex in Harare, Zimbabwe,[18] stays cool without air conditioning and uses only 10% of the energy of a conventional building of the same size.In structural engineering, the Swiss Federal Institute of Technology (EPFL) has incorporated biomimetic characteristics in an adaptive deployable "tensegrity" bridge. The bridge can carry out self-diagnosis and self-repair.[19]
Technologies
Practical underwater adhesion is an engineering challenge since current technology is unable to stick surface strongly underwater because of barriers such as hydration layers and contaminants on surfaces. However, marine mussels can stick easily and efficiently to surfaces underwater under the harsh conditions of the ocean. They use strong filaments to adhere to rocks in the inter-tidal zones of wave-swept beaches, preventing them from being swept away in strong sea currents. Mussel foot proteins attach the filaments to rocks, boats and practically any surface in nature including other mussels. These proteins contain a mix of amino acid residues which has been adapted specifically for adhesive purposes. Researchers from the University of California Santa Barbara borrowed and simplified chemistries that the mussel foot uses to overcome this engineering challenge of wet adhesion to create copolyampholytes,[20] and one-component adhesive systems[21] with potential for employment in nanofabrication protocols.Spider web silk is as strong as the Kevlar used in bulletproof vests. Engineers could in principle use such a material, if it could be reengineered to have a long enough life, for parachute lines, suspension bridge cables, artificial ligaments for medicine, and other purposes.[12] 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.[18] Murray's law, which in conventional form determined the optimum diameter of blood vessels, has been re-derived to provide simple equations for the pipe or tube diameter which gives a minimum mass engineering system.[22] Aircraft wing design [3] and flight techniques[23] are being inspired by birds and bats.
The BionicKangaroo reproduces the jumping locomotion of a kangaroo, bouncing to recover much of the energy of each jump.
Biorobots based on the physiology and methods of locomotion of animals include BionicKangaroo which moves like a kangaroo, saving energy from one jump and transferring it to its next jump,[24] and climbing robots,[25] boots and tape[26] mimicking geckos feet and their ability for adhesive reversal. Kamigami Robots, a children's toy, mimic cockroach locomotion to run quickly and efficiently over indoor and outdoor surfaces.[27] Nanotechnology surfaces that recreate properties of shark skin are intended to enable more efficient movement through water.[28] Tire treads have been inspired by the toe pads of tree frogs.[29] The self-sharpening teeth of many animals have been copied to make better cutting tools.[30] Protein folding has been used to control material formation for self-assembled functional nanostructures.[31] The structural coloration of butterfly wings has been adapted to provide improved interferometric modulator displays and everlasting colours.[32] New ceramics copy the properties of seashells.[33] Polar bear fur has inspired the design of thermal collectors and clothing.[34] The arrangement of leaves on a plant has been adapted for better solar power collection.[35] The light refractive properties of the moth's eye has been studied to reduce the reflectivity of solar panels.[36] Self-healing materials, polymers and composite materials capable of mending cracks have been produced based on biological materials.[37]
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.[38]
Most viruses have an outer capsule 20 to 300 nm in diameter. Virus capsules are remarkably robust and capable of withstanding temperatures as high as 60 °C; they are stable across the pH range 2-10.[13] Viral capsules can be used to create 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 which can induce nucleation of crystal growth. This was demonstrated through the production of platinum and gold nanotubes using TMV as a template.[39] Mineralized virus particles have been shown to withstand various pH values by mineralizing the viruses with different materials such as silicon, PbS, and CdS and could therefore serve as a useful carriers of material.[40] A spherical plant virus called cowpea chlorotic mottle virus (CCMV) has interesting expanding properties when exposed to environments of pH higher than 6.5. Above this pH, 60 independent pores with diameters about 2 nm begin to exchange substance with the environment. The structural transition of the viral capsid can be utilized in Biomorphic mineralization for selective uptake and deposition of minerals by controlling the solution pH. Possible applications include using the viral cage to produce uniformly shaped and sized quantum dot semiconductor nanoparticles through a series of pH washes. This is an alternative to the apoferritin cage technique currently used to synthesize uniform CdSe nanoparticles.[41] Such materials could also be used for targeted drug delivery since particles release contents upon exposure to specific pH levels.
Surface tension biomimetics are being researched for technologies such as hydrophobic or hydrophilic coatings and microactuators.[42][43][44][45][46]
Biomimetic materials are gaining increasing attention in the field of optics and photonics. For example, the chiral self-assembly of cellulose inspired by the Pollia condensata berry has been exploited to make optically active films.[47] Similarly, phase-separation has been used to fabricate ultra-white scattering membranes from polymethylmethacrylate, mimicking the extraordinary properties of the beetle Cyphochilus.
