More recently, the structures created by bees have been mimicked to produce lightweight, strong honeycomb-structured materials, and Velcro, invented by George de Mestral, who noticed how burdock seeds stuck in his dog’s coat, is now a widely used fastening system.
The mimicry of biomimetics can take a variety of forms. A material may look, feel and react like a biological species or simply be inspired by nature. Biomimicry is really about what we can learn and apply from biological systems.
Although humans have endeavored to do this for millennia, we now have far more advanced techniques to help us replicate or imitate nature, and we can do so at a molecular level.
Although biomimetic materials are sometimes referred to as ‘biomaterials’, this is a misnomer. Biomaterials is a more general term covering natural or synthetic materials that either contain living cells or replicate biological functions for medical applications.
‘Smart materials’, another frequently heard term, refers to special biomimetic materials such as shape memory alloys that exhibit a response to external stimuli.
The simplicity of many biomimetic materials is not only exciting but is also leading to elegant and clever applications in efficient and sustainable objects and systems.
Designers are now able to conceive and implement radically new, and much more sophisticated, design responses – particularly with regard to economy of materials and sustainable practices.
For instance, an electronic device might consist of a sensor, a microprocessor, a power supply (battery) and a motor – yet there are biomimetic materials such as smart hydrogels, shape memory alloys and polymers that can move in response to all sorts of stimuli on their own, without the need for all of these components. So, products can be designed with fewer components that are not necessarily bound by component geometry.
The principle of biomimicry is also of interest to designers, engineers and manufacturers. Designers and engineers often draw their inspiration for ‘products’ from nature – either by exploring form (as in Ross Lovegrove’s work), or for functional reasons (such as the development of elegant structures and mechanical systems).
In the design of complex systems for crowd control, computer networking and traffic management, the study of ants and ant colonies is proving a fruitful area. Locusts have also been studied to help with the development of advanced collision-avoiding sensors.
For manufacturers, biomimicry has much to offer. The majority of products are made by additive (adding components together), subtractive (machining material) or deforming (bending, folding) manufacturing processes, or else by changing the states of material (casting, moulding).
Biological systems, by contrast, typically grow materials or build on site using the organism as a chemical manufacturing plant to simultaneously produce raw materials and construction in one, and so are far more efficient.
One only has to look at the miraculous constructions created by insects and arachnids to realise how inefficient our building and manufacturing practices are by comparison.
For instance, a bee hive, termite mound or spider’s web is an extremely sophisticated structure that is quick to make, incredibly economic in its use of material, and results in a very smart multifunctional system (a spider’s web can be home, lifeline, food harvester and barometer, amongst other things that we still may not have discovered).
Spider silk is extremely tough and strong, and scientists are developing synthetic versions for the healing of wounds (stitches, bandages and biomedical applications), prevention of wounds (bullet-proof clothing), and the creation of super-strong, lightweight and tough materials.
The Oxford Silk Group at the University of Oxford is examining a number of phenomena related to spider silk and webs. Aside from the material itself, the way in which spiders spin silk and the resulting web structures have incredible implications for design, via the development of more advanced extrusion processes (for plastics and textile industries), or ultra lightweight structures.
The gecko’s remarkable ability to defy gravity by walking up walls and upside down across ceilings is also generating a lot of interest. The gecko’s secret is the nanoscopic ‘hairs’ on its toes, which generate incredibly strong capillary and van der Waals forces that counteract gravitational forces.
With advances in nanofabrication technologies, an artificial material with similar properties to gecko skin has been developed.
A research team at the University of Manchester have developed ‘gecko tape’ – a form of dry adhesive that can be repositioned on smooth surfaces – and have, rather humourously, demonstrated the potential of the tape by suspending a toy Spiderman doll from the ceiling, held only by a small strip of tape on the toy’s hand.
Leaves are another fruitful area of research. The lotus leaf, for example, has the remarkable ability to self-clean. Upon the surface of the leaf are thousands of microscopic ‘spikes’ that resist water.
When it rains, water droplets sit proud of the leaf, and as the droplets roll off the leaf, dirt particles are lifted from the leaf surface by the water droplets and taken away.
This phenomenon has been replicated in a number of commercial products including Pilkington’s Activ self-cleaning glass, and Sto Lotusan water-repellent coatings.
Leaves may also help us come up with new means of energy production. The Molecular Electronics group at the University of Arizona is examining how leaves store energy and is replicating photosynthetic reactions in order to develop miniature solar cells and batteries.
The marine world is one of the most active areas of investigation. Based on kelp found in Botany Bay, Sydney, Professors Peter Steinberg and Staffan Kjelleberg from the University of New South Wales have developed biofilms that repel bacteria.
A spin-off company, Biosignal, now produces antifouling paints, coatings for contact lenses, and antibacterial coatings for medical devices.
A number of universities, and a research program funded by the Swedish Foundation for Strategic Research, are investigating the properties of sharkskin. Sharks can swim very fast, in part due to the physical properties of their skin, which appears rough. This roughness creates little eddies (or turbulence) as the shark glides through the water, thus reducing friction.
With the application of microfabrication and nanofabrication, low-friction materials and coatings mimicking sharkskin are being developed for a variety of applications, including making boats and watercraft faster and reducing the friction in pipes. FastSkin FSII, a material developed by Speedo for swimming apparel, is another application derived from sharkskin research.
Other marine creatures are also being investigated, including blue mussels, which produce an adhesive that can set and stick underwater; phosphorescent algae; and cuttlefish, which have astounding camouflage capabilities. Diatoms, a common type of phytoplankton, have cells made of silica.
Daniel Morse from the University of California, Santa Barbara, has developed a process, inspired by these creatures, to produce silica. It may lead to techniques for producing silicon chipsets with less energy and fewer toxins than current processes, as well as to new ways to stimulate bone growth to treat osteoporosis.
Our own body, and blood in particular, is providing inspiration for new materials, too. Self-healing polymers, developed to prevent crack propagation and failure in materials, mimic the way blood coagulates to stop wounds bleeding.
The polymers contain two types of microcapsules – one containing uncatalysed resin and the other a catalyst. When a crack appears, the capsules rupture and react with one another to harden and plug up the gap. Utilising this technology, chip-resistant paint for cars, light aircraft and marine craft is currently in development.
Liposomes are spherical vessels with a double membrane and can be used for drug delivery within the body. Their natural attraction to cancer cells and tumours means they can be used to target cancer.
Nanotubes and liposomes can also be used to create biological computer networks, by mimicking how biological cells function. Carbon nanotubes are molecular-scale tubes of perfectly ordered carbon that have incredible electrical properties and present great opportunities for the development of new generations of computer processors.
DNA strands have been used to perform computational functions, too, and living neuron cells have been incorporated into silicon-based processors.
Eyes are another site of interest for biomimetics. Biocompatible hydrogels, polymers that can retain water and simulate biological tissue, are used to create more comfortable and longer-lasting contact lenses, and Stanford University’s Bio-X interdisciplinary research program (amongst others) has worked on developing a biocompatible artificial cornea for use in eye surgery.
By studying the incredible array of ingenious and sophisticated materials and manufacturing processes that exist in nature we can fast-track our knowledge base and extend our repertoire of materials and processes. The resultant biomimetic materials offer fascinating possibilities and so extend our potential to come up with new ideas.
But we should also tread warily. There is a lot we do not know about some of these materials, so some may not be that safe to fully utilise. For instance, some nanomaterials such as carbon nanotubes are so small they can penetrate cells and tissues in our bodies and therefore may do all sorts of harm.
The potential to be more economic in our consumption of raw resources in the long run is of particular appeal, but currently many of the processes used to generate these materials are rather inefficient in terms of time, money, energy and other resources.
Nature has a lot to teach us, particularly with regard to the economic use of materials and sustainable practices. While a lot of these materials are expensive to produce, research is underway to develop cheaper manufacturing processes.
The biotechnological applications of biomimicry are both wonderful and potentially frightening, and the ways in which the technologies may be implemented is an important ethical issue to consider.
Like any technology, whilst the materials may be amoral, the purpose for which they are implemented may not be. Biomimetic materials are being researched throughout the world, in small research labs in universities as well as in large corporate and government organisations.
NASA funds a lot of work, and there is interest, of course, from chemical and pharmaceutical companies and the military. The source of the funding for the development is usually the indicator of ultimate purpose.
We would like to acknowledge the assistance of Jonathon Allen, whose expert knowledge of materials provided the basis of this story.