After returning home from a five-year voyage around the world on the HMS Beagle, English naturalist Charles Darwin began to formulate what would eventually become one of the best substantiated theories in the history of science. The theory of evolution, first published in his seminal 1859 book On the Origin of Species, states that populations change over the course of generations through the process of natural selection. Individuals best suited to their environment are more likely to survive and reproduce, while those not suited to their environment are less likely to do so.
What Darwin may not have predicted, however, was that humankind would later harness the power of evolution for its own benefit. In particular, researchers inspired by his groundbreaking biological theory learned to mimic the process of natural selection in the lab — a method called “directed evolution” — to develop customised proteins of interest. Today, these proteins can manufacture everything from biofuels to pharmaceuticals. In 2018, Frances H. Arnold, George P. Smith, and Sir Gregory P. Winter won the Nobel Prize in Chemistry for their revolutionary work on directed evolution.
Billions of years of evolution have created an incredible degree of complexity to life on Earth. Not only are scientists and engineers trying to master evolution itself, but they also want to mimic the high-performance results of natural evolution — for instance, ultra-strong and lightweight spider silk, tail regeneration in lizards, and the excellent aerodynamics of birds. Disciplines such as bionics and biomimetics take inspiration from the biological methods and systems found in nature to tackle human problems, while also furthering our understanding of physics, engineering, and technology
Termites Mounds, Electric Eels, and Gecko Ears
Bionics is the science of constructing artificial systems that have some of the characteristics of living systems. For instance, the idea behind Velcro came to Swiss engineer and amateur mountaineer George de Mestral after a hike in the woods. He noticed the burrs that stuck fast to his clothes with tiny hooks and wondered if he could mimic the design for a commercial application. Eight years later, de Mestral introduced Velcro to the world, the now-ubiquitous “zipper-less zipper” consisting of two complementary strips with tiny hooks and loops.
Biomimetics is a closely related field that has a more general focus, expanding the concept of emulating nature to less science and technology-driven areas such as product design, architecture, and art. An office building in Zimbabwe, for example, has an internal climate control system originally inspired by the structure of termite mounds. These insects build vertical mounds out of soil, saliva, and dung that maintain a constant internal temperature despite huge fluctuations in outside temperature. The Eastgate Centre in Harare has no conventional air conditioning or heating system, yet stays regulated year-round with a ventilation system modeled after the many heating and cooling vents of a termite mound.
Both fields have made significant strides towards our understanding of physics and engineering, while also providing innovative solutions. In 2017, a team led by biophysicist Michael Mayer of the University of Fribourg created a new type of soft, foldable battery inspired by the electric eel. The fish has 6,000 cells called electrocytes that store power like tiny batteries and can simultaneously discharge in order to deliver a strong electric shock.
Mayer and his colleagues mimicked the eel’s electrocytes by printing out rows of hydrogel dots on sheets of plastic, alternating a dot containing sodium chloride with one containing only water. They printed a second sheet of plastic with two more types of hydrogel dots, one of which would allow the passage of only cations and one that could only conduct anions. When these two sheets are pressed together, the system generates power. Such a power source could one day power implantable or wearable devices, like a pacemaker or biological sensor.
Late last year, a group led by material scientist Mark Brongersma of Stanford University developed a new photodetector inspired by the unique ears of geckos. Larger animals are able to sense the directionality of sounds by recognizing the intensity and time differences of the wave hitting its two ears. But small animals like the gecko — whose ear-to-ear spacing is shorter than audible sound wavelengths — can’t triangulate the location of noises in the same way. Instead, the lizards have a small tunnel through their heads that measures the way incoming sound waves bounce around to figure out directionality.
Brongersma and his colleagues created a similar system for detecting the angle of incoming light with a sub-wavelength photodetection pixel, which are typically only 1/100th of the thickness of a hair. The system uses two closely spaced silicon nanowires and was the first to demonstrate the feasibility of detecting light directionality with such a small setup. Basically, when light hits the photodetector at an angle, the wire closest to the source interferes with the waves impinging on the other. The first wire to detect the light sends the strongest current, and after some calculations that involve comparing the current in both wires, the directionality of the light source can be mapped out
The Past and Future of Biomimicry
Other examples that showcase the sheer innovation of bionics and biomimetics abound, particularly when it comes to fields like physics, engineering, and technology. Mimicry of nature isn’t a new idea — in fact, Leonardo da Vinci studied the anatomy of birds to design a flying machine back in the 15th century — yet it shows no signs of slowing down in terms of contributions to new ideas and inventions. Even though humans have evolved to possess large, complex brains and advanced societies, bionics and biomimetics are proof that we still have so much to learn from the natural world around us.