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15

Functional Surfaces in Biology:
Mechanisms and Applications

Stanislav N. Gorb

CONTENTS
15.1 Introduction: Functions of Biological Surfaces ................................................................................. 381
15.2 Surfaces of Joints and Skin: Antifriction and Drag Reduction ......................................................... 382
15.3 Attachment Systems........................................................................................................................... 384
15.4 Anti-Adhesive and Self-Cleaning Surfaces ....................................................................................... 390
15.5 Optics.................................................................................................................................................. 391
15.6 Thermoregulation and Prevention of Drying..................................................................................... 392
15.7 Sound Generation ............................................................................................................................... 393
15.8 Defense, Grooming, Sampling, Filtrating, Grinding ......................................................................... 393
15.9 Biomimetics of Surfaces: What Can We Learn from Evolution?..................................................... 394
Acknowledgments .......................................................................................................................................... 394
References....................................................................................................................................................... 394

15.1 INTRODUCTION: FUNCTIONS OF BIOLOGICAL SURFACES

Biological surfaces represent the interface between living organisms and the environment and serve
many different functions: (1) They delimit dimensions, often give shape to the organism, and
provide mechanical stability to the body. (2) They are barriers against dry, wet, cold, or hot
environments. (3) They take part in respiration and in the transport of diverse secretions, and
serve as a chemical reservoir for the storage of metabolic waste products. (4) A variety of
specialized surface structures are parts of mechano- and chemoreceptors. (5) The coloration and
chemical components of surfaces are important components for thermoregulation, and are often
involved in diverse communication systems. (6) A number of specialized surface structures may
serve a variety of other functions, such as air retention, food grinding, body cleaning, etc.
There are numerous publications describing biological surfaces by the use of light and electron
microscopy. Because of the structural and chemical complexity of biological surfaces, exact
working mechanisms have been clarified only for a few systems. However, biological surfaces
hide a virtually endless potential of technological ideas for the development of new materials and
systems. Because of the broad diversity of functions, inspirations from biological surfaces may be
interesting for a broad range of topics in engineering sciences: adhesion, friction, wear, lubrication,
filtering, sensorics, wetting phenomena, self-cleaning, antifouling, thermoregulation, optics, and so
on. Since all biological surfaces are multifunctional, it makes them even more interesting from the

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