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394 Biomimetics: Biologically Inspired Technologies

15.9 BIOMIMETICS OF SURFACES: WHAT CAN WE LEARN FROM EVOLUTION?

Throughout evolution, nature has constantly been called upon to act as an engineer in solving
surface-related technical problems. Organisms have evolved an immense variety of shapes and
structures. Although often intricate and fragile, they can nonetheless deal with extreme mechanical
loads. This chapter has demonstrated that many functions are based on a variety of ingenious
surface-related solutions. The success of biologically inspired technological surfaces is an indica-
tion that knowledge from biology is also highly relevant for technical applications.
One of the greatest challenges for today’s engineering science is miniaturization. Many organ-
isms have solved many problems correlated with extremely small size, during their evolution.
Zoologists and botanists have collected a huge amount of information about the structure of such
living micromechanical systems. This information can be utilized to mimic them for further
industrial developments. An important feature of the evolution of functional surfaces is the multiple
origins of similar solutions in different lineages of living organisms, and in different functional
systems. For example, there is no doubt that attachment systems consisting of a pair of microtrichia-
covered surfaces appeared independently in the head-arresting system of Odonata, coxal-locking
devices of Neuroptera, and the elytra-locking system of Coleoptera (Gorb, 1999, 2001). In the case
of locomotory attachment devices, hairy pads appeared three times independently within insects
and additionally at least two times within other animals (Gorb and Beutel, 2001). Also, similar
optical structures, made of different materials, have been described for insects, birds, and plants
(Vukusic and Sambles, 2003). Such examples of convergence are the most interesting from the
engineering point of view, because they indicate a kind of optimal solution for a particular problem.
These examples should be the very first candidates for biomimetics.
An engineering approach, applied after detailed studies on the natural system, involving
modeling and then prototyping, would be most promising. However, in some cases, engineers
can also, simply copy the surface shape and replicate it at a variety of scales and materials using
available technologies of chemistry and processing. Both approaches may run parallel for some
time and possibly converge later.

ACKNOWLEDGMENTS

The author is very thankful to the members of the Biological Microtribology Group at MPI
for Developmental Biology (Tu ¨bingen, Germany) and Evolutionary Biomaterials Group at
MPI for Metals Research (Stuttgart, Germany) for the fruitful joint work on various surface-related
projects. Valuable suggestions of John Barnes (University of Glasgow, Glasgow, UK), the Editor,
and four reviewers on the text of this review are greatly acknowledged.

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