Biomimicry and Product Design (Part 2) - How Nature Works and its Optimisation Process

Nature is a very complex process and a complete understanding, demands an extensive description of its primary means. How the full explanation is not the aim of this study, will be described here a selection of principles and philosophy that better can fit with the product design and development process and how it can fits with Topology Optimisation.

Holistic and Mechanistic Philosophy

·    Holistic philosophy: Systems and their proprieties should be viewed as wholes, not as collections of parts. It means that to understand one part is necessary to understand how the whole influence it, and how this part influences the whole. The events of systems are cyclic, not linear.

·    Mechanistic philosophy:  A complex system can be understood and explained as segregation and reduction of parts in a hieratic model, wherein the whole is the sum of all parts, and with linear and predictable events, in a Cartesian view. This paradigm has emerged around the 18th century during the Enlightenment, broking down the world into various disciplines.

All the natural biological systems work holistically. It is not possible to develop some piece or system that is sustainable, without looking the whole and mutual influences and dependencies. The Modern Age is still in mechanistic paradigm, the reason that why all development created has not been successful in being sustainable, and at this time, the human species is in a point that is necessary change the paradigm to survive in long-term (Capra, 1982). 

Nature Principles to Sustainability

All nature creations tend to be sustainable if not, those tend to be eliminated along the time. While creation and natural evolution features do self-feedback loops such as learn and adapt, the human artefacts yet do not

There are nine principles that govern and define how nature operates that make it sustainable (Benyus, 2009):

                                    I.           Nature runs on sunlight

                                  II.           Nature uses only the energy it needs

                                 III.           Nature fits form to function

                                 IV.           Nature recycles everything

                                  V.          Nature rewards cooperation

                                 VI.           Nature banks diversity

                               VII.           Nature demands local expertise

                              VIII.          Nature curbs excesses from within

                                 IX.           Nature taps the power of limits

As a complementary idea, The Biomimicry Institute suggest that six principles allow for life exist. These are shown in (Figure 1, Figure 2, Figure 3).

Figure 1 - Life´s principles of Biomimicry 3.8. FONT: The Biomimicry Institute.

Figure 2 - Six principles of life. FONT: The Biomimicry Institute.

Figure 3 - The six life's principles explanation. FONT: The Biomimicry Institute.

Darwin´s Evolution Theory

Formulated in 1859 (around one century before the DNA discovery) with the publication of book On the Origin of Species, written by naturalist Charles Darwin, being it nowadays, the most acceptable base of the evolution theory. The theory assumes that changes over time are a result of changes in heritable physical or behavioural traits. The theory works around two points. One is that all life is connected and related to each other, in an endless searching for a balance. The cooperation is essential to the survival of all system, instead of competition, that happens only between niches. The other point is that the life diversity is due to modifications in populations driven by natural selection.

The natural selection is defined as the survival of the fittest, and be the fittest is defined as who has the ability to survive and to reproduce face to external threats. Natural selection changes the species in two scales, small and big. The small-scale, called microevolution, changes gradually particular characteristic, such as colour or size, along with generations (it can be seen as a bottom-up modification). With an accumulation of micro changes along a very long time, the big-scale, called macroevolution, can create entirely new species. Another key factor of the natural selection is the ability to the success of an organism attract a mate, called Sexual Selection (Than & Live Science, 2018). The Sexual Selection is so essential, that is common many species has created special modifications or behaviour, that requires a lot of quantity of energy and material just to guarantee the reproductive success, even than these special characteristics in nothing influence the daily survival actions, such as, eat, hunt, escape etc (Figure 4). The sexual importance to the life, including the humans, had been defended by Freud with the concept of sexual drive, as being one of the most significant drive forces of the human behaviour (Encyclopaedia Britannica, n.d.; Kandel, 2012; Stoléru, 2014), influencing deeply the unconscious and acting in the most of intellectual productions and artistic manifestations, spreading until to the product design.

Figure 4 - Sexual animal ornaments. At left picture a male moose displaying antlers. At right picture a Male peacock showing its tail. FONT: Study.com

  The small physical or behavioural changes happen due random genetic modification in the reproduction of DNA passed to the new generations. It means that evolution creates information, increasing its complexity along the time in a process that never stops. However, it does not mean that all generation mutated is better than previous one. Better or worse organisms can be created but is the natural selection that will make the best survives. That suggests that the evolution is a process aimed to try and errors, through random changes. Moreover, the concept of better or worse is relative, depending on the external circumstances for that specific time. Thus, the evolution process never comes back, or by other words, the evolution process creates information, but does not have “memory”.

The time scale to note significant changing in species from evolution is of thousands or millions of years. For human perception, this scale of time is hard to imagine, but the planet Earth has around 4.5 billion years old. The life started to appear about 3.8 billion years with single-celled prokaryotic cells, such as bacteria. Only at last 570 million of years ago, is that more complex life forms start to appear with arthropods. Land plants have emerged around 475 million of years ago. Mammals have approximately 200 million of years ago, and the Homo sapiens has only 200 thousand years ago (0,004% of Earth´s age) (BBC, 2018) (Figure 5). During all this period, the nature has created more than 30 million of species (Benyus, 2009).

Figure 5 - The geologic time scale (GTS) from the origin of the earth to human origin. FONT: IAS4Sure.

Some of the optimisation algorithms are based on evolutionary concepts, using nature-inspired strategies.

Types of Evolution

Over the time, the evolution can follow different patterns. Three more common patterns are convergent, divergent and parallel.

Convergent

When different species with different ancestry have similar characteristics (behaviour, structure, anatomy, appearance etc). This convergence happens due environment and other survival pressure in common to the species. Structures created by convergent evolution are called of Analogous Structures or Homoplasies. Example of convergent evolution are birds, insects and bats. All they created wings to supply the same need, that is fly (Figure 6).

Divergent

When different species have different characteristics, but are from the same ancestry. This divergence happens when a group migrates to another environment. The divergence is responsible for life diversification of species and breed. Some species may develop Homologous Structures, that are anatomically similar, with similar functions from a common ancestor (Figure 7).

Parallel

When different species evolves along the time maintaining the same level of common characteristics. These species do not necessary have neither a common ancestor or environment or survival pressures. But, they had created similar adaptations strategies. Plants are a good example of parallel evolution.

Understanding these differences allows finding some similar behaviour in the TO process. In particular to the convergence, and to homologous structures, supposing that structures with similar boundary conditions but with different applications could create similar solutions, and use it for standardisation of parts to decrease manufacturing costs.

Figure 6 – Example of convergent evolution with wings of a pterosaur, bat and bird. All species have no common ancestor, but all they created wings to the same function, that is fly. Bones with the same colour are homologous structures. FONT: National Center for Science Education.

Figure 7 –  Species from divergent evolution, with the common ancestor (vertebrates). Bones with the same colour are homologous structures. FONT: Biology Dictionary.

Wolff’s Law

Formulated in 1892 by anatomist and orthopaedic surgeon Julius Wolff, in his book “The Law of Bone Remodeling”, translated from German to English in 1986, the Wolff´s Law states (Wolff, 1986):

Every change in the form and the function of a bone or of their function alone is followed by certain definite changes in their internal architecture and equally definite secondary alterations in their external conformation, in accordance with

mathematical laws. (p.225)

In other words, it means that a bone in a healthy organism will adapt to changes in loads (intensity or directions), first in remodel of its internal architecture (trabeculae), followed by remodelling of its external portion changing its thickness, in a dynamic process (the skeletons are constantly changing). If loads increase, the bone becomes more density and stronger, if decrease, it loses mass and become weaker.

Another consequences of this adaptation process are: The ratio between strength and weight is optimised; The trabeculae will be aligned with principal stress directions; The self-regulation of bone cells is a response due to mechanical stimulus (Folgado & Fernandes, 2011) (Figure 8). 

Figure 8 - In the left, a section of a femur showing trabecular structure. In the middle, the representation of principal stress directions (Meyer, 1867). On the right, the stress trajectories in a model analysed by Culmann. The curves are the representation of the orientations of maximal and minimal principal stresses trajectories that always intersect perpendicularly. Adapted from (Wolff, 1986)(translation). FONT: (Huiskes, 2000). 

This density adaptation process of bone is an interactive optimisation process that minimises the strain energy and ponders the relativity densities as optimisation variables. A process similar in a Topology Optimization process in which the variable to optimise is the bone density, (that will add/increase the material density in higher stress regions and decrease/remove from lower stress regions). For this reason, the TO can be used as a useful tool in biomechanical, for remodelling and adaptations models to bones (Oliveira, Ramos, Simões, Pinho-da-cruz, & Andrade-Campos, 2009).

Bibliography:

BBC. (2018). History of life on Earth. Retrieved April 22, 2018, from http://www.bbc.co.uk/nature/history_of_the_earth

Benyus, J. M. (2009). Biomimicry: Innovation Inspired by Nature. New York: HarperCollins. Retrieved from https://books.google.pt/books?id=mDHKVQyJ94gC

Capra, F. (1982). The turning point: Science, society, and the rising culture. New York: Simon and Schuster.

Encyclopaedia Britannica. (n.d.). Sexual motivation. Retrieved April 22, 2018, from https://www.britannica.com/topic/sexual-motivation

Folgado, J., & Fernandes, P. R. (2011). Bone Tissue Mechanics.

Huiskes, R. (2000). If bones is the answer, then what is the question? Journal of Anatomy, 197, 145–156.

Kandel, E. (2012). The Age of Insight: The Quest to Understand the Unconscious in Art, Mind, and Brain, from Vienna 1900 to the Present (3.1). New York: Random House.

Meyer, G. (1867). Die Architektur der Spongiosa. Archief Fur Den Anatomischen Und Physiologischen Wissenschaften Im Medicin.

Oliveira, J. A., Ramos, A., Simões, J. A., Pinho-da-cruz, J. A., & Andrade-Campos, A. (2009). Influência da Malha de Elementos Finitos no Pocesso de Remodelação Óssea. 3^o Congresso Nacional de Biomecânica.

Stoléru, S. (2014). Reading the Freudian theory of sexual drives from a functional neuroimaging perspective. Frontiers in Human Neuroscience, 8(March), 1–15. https://doi.org/10.3389/fnhum.2014.00157

Than, K., & Live Science. (2018). What is Darwin’s Theory of Evolution? Retrieved April 22, 2018, from https://www.livescience.com/474-controversy-evolution-works.html

Wolff, J. (1986). The Law of Bone Remodelling. (R. Furlong & P. Maquet, Eds.). Berlin: Springer-Verlag Berlin Heidelberg. https://doi.org/10.1007/978-3-642-71031-5