Nature: The Design Mentor

Introduction

Bio-mimetics, Bio-inspiration, Natural engineering, Bionics, etc., stand for widely spreading trends in the technological world. A tool common among these trends is scouring technical solutions available in the natural world then; transfer them to the human engineering domain. Although the previous terms are of recent origin, the underlying concept is deeply rooted in antiquity. Indeed, inspiration by nature dates back to primitive man. Human fascination with nature is rooted in the harmonic expression of form, function, and proportion often observed in our surroundings. Throughout history, humans sought to identify a perceived “heavenly order” manifested as beauty, order, or optimality of function.

There are many examples in nature that reflect optimized “smart” function. One intriguing example is that of bees (Hales, 2001). Humans have recognized the brilliance of constructing beehives since at least two millennia, especially when the relation between the hexagonal shape of the unit cell and the economy of material (wax in this case) is considered. The earliest claim of such knowledge appeared as early as 36 B.C., in the writings of Marcus Terentius Varro within his book on agriculture. He supported the claim that the hexagonal structure was explained by the isoperimetric property of the hexagonal honeycomb:¹

Toth (Tóth, 1964) alluded to the same property and explained that the three-dimensional problem of shaping the ends of the hexagonal cells to interlock with the ends of the cells on the other side is quite complex. Interestingly, according to his calculations, he concluded that the material in the bees' idealized three-dimensional structure can be reduced by a fraction of one percent. In 1999 Hales (2001) proved that a honeycomb of regular hexagons is the most efficient way to partition the plane into unit areas (using the least amount of average amount of material). In the world of the beehives, this statement confirms that bees have practically solved a recondite problem, and have made their cells of the proper shape to hold the greatest possible amount of honey, with the least possible consumption of precious wax in their construction.

Branch compliance presents a major problem for arboreal animals that travel and feed in the forest canopy. Branches taper towards their ends, but the narrowest gaps between trees are situated between the thin terminal branches of adjacent tree crowns. Efficient travel through the rainforest canopy requires animals to minimize the deviations from their travel path, unless such deviations are more energetically efficient than direct travel (although non-energetic factors such as the risk of falls may also influence gap-crossing decisions). In theory, compliant terminal branches may act as external springs adding momentum to jumps and leaps across gaps, but most researchers have suggested that compliant supports increase the cost of arboreal locomotion. Alexander (1991) showed that quadrupedal monkeys lose energy during takeoff and landing as branches bend under their weight and jumping lemurs generally lose contact with branches before they recoil, expending energy to deform supports but failing to exploit the elastic energy to aid momentum. However, field observations suggest that some primates can use branch compliance to their advantage: galagos and pygmy chimpanzees (Pan paniscus) use branches as catapults (Cant, 1987) and various species pump branches prior to leaps to make use of the propulsive force of branch recoil (Cant, 1994). Recent studies of orangutans offer increasing evidence that many aspects of their gap-crossing behaviour use elastic energy stored in compliant branches (Alexander, 1991, Cant, 1987, Cant, 1994, Demes et al.,1995, Markham and Groves, 1990), even though their large body mass might be expected to render arboreal gap crossings energetically costly and a safety risk. The best documented example of orangutans using support compliance is tree sway, in which individuals oscillate thin vertical tree trunks with increasing magnitude until a support on the opposite side of the gap may be reached (Demes et al.,1995, Markham and Groves, 1990, Thorpe and, Crompton 2005, Thorpe and Crompton, 2006)