1.1 Historical Perspectives
Living organisms in nature have evolved over billions of years to produce a variety of unique materials that possess extraordinary abilities or characteristics, such as selfâcleaning, selfâhealing, efficient energy conversion, brilliant structural colors, intelligence, and so on. These biological materials are made by nature using earthâabundant elements at ambient temperature, pressure, and neutral pH. Mimicking these biological materials structures and processing could lead to the development of a new class of advanced engineering materials useful for various applications ranging from transportation (e.g., aircraft and automobiles) to energy production (e.g., turbine blades, artificial photosynthesis), to biomedical products (e.g., implants, drug delivery). Some of these solutions provided by nature have inspired humans to achieve outstanding outcomes. For example, artificial dry adhesives mimicking gecko foot hairs have shown strong adhesion, 10 times higher than what a gecko can achieve,1 and the strength and stiffness of the hexagonal honeycomb have led to its adoption for use in lightweight structures in airplane and other applications.2
The idea of mimicking natureâs materials design has been around for thousands of years. Since the Chinese attempted to make artificial silk over 3000 years ago2 there have been many examples of humans learning from nature to design new materials and related products. One of historyâs great inventors, Leonardo da Vinci, is well known for his studies of living forms and for his inventions, which were often based on ideas derived from nature.3 Although the lessons learned by da Vinci and others were not always successful, as seen in the countless efforts throughout the ages by humans to fly like a bird, these explorations provided some clue for the Wright brothers, who designed a successful airplane after realizing that birds do not flap their wings continuously, rather they glide on air currents.4 Perhaps the most common and successful product developed based on bioinspiration is Velcro, a fastener. In the 1940s a Swiss engineer, George de Mestral, noticed how the seeds of an Alpine plant called burdock stuck to his dog's fur. Under a microscope, he saw that the seeds had hundreds of tiny hooks that caught on the hairs. This unique biological material structure inspired him to invent the nylonâbased fastener that is now commonly used.
Although the idea of learning from nature has been around for a long time, the science of biomimetics has gained popularity relatively recently. This approach, which uses natureâs blueprints to design and fabricate materials, dates back to the 1950s, when the term âbiomimeticsâ was first introduced by Schmitt in 1957.5 Biomimetics is derived from bios, meaning life (Greek), and mimesis, meaning to imitate.6 The term âbionicsâ was introduced by Steele7 as âthe science of systems, which has some function copied from nature, or which represents characteristics of natural systems or their analoguesâ. The term âbiomimicryâ, or imitation of nature, coined by Janine Benyus in 1997, refers to âcopying or adaptation or derivation from biologyâ.8 From a materials science and engineering perspective, the science of biomimetic materials is thus the application of biological methods and principles found in nature to the study and design of engineering materials. This ânewâ science is based on the fundamentals of materials science and engineering, but takes ideas and concepts from nature and implements them in a field of technology. While the term âbiomimeticâ is frequently used in this book to describe mimicking the microstructure of biological materials, âbioinspiredâ is also employed to describe more general inspiration from nature.
The variety of life is huge; many things fascinate us. Leaves use sunlight, water, and carbon dioxide to produce fuel and oxygen. Geckos keep their sticky feet clean while running on dusty walls and ceilings. Some kinds of bacteria thrive in harmful environments by producing enzymes that break down toxic substances. Materials scientists are increasingly interested in how these phenomena work, and applying this knowledge to create new materials for clean energy conversion and storage, reusable selfâcleaning adhesives, cleaning up pollution, and much more. Once the biomimicking succeeds, the impact is enormous.