teaching
Evolutionary Biomaterials Group

 

FrictionAdhesionMaterial


anmat2

Arthropod cuticle is a composite material made up of two constituents: chitin fibers and protein matrix. The cuticle is subdivided into two main layers epicuticle and procuticle. Also keratin-containing materials, such as snake skin, gecko setae, bird feathers are studied (figure: SEM picture of the fracture of insect cuticle)

The plant materials are organised into several hierarchical layers.Plant actuators and wax layers are the most interesting systems under considerartion (figure: phase-contrast image of a frozen section of plant material)

Detailed information about the correlation of the mechanical properties and the structure of biological materials may aid in understanding the relationship between structure and function (figure: SEM picture of beetle terminal elements attaching to surface irregularities. This visualises contact behaviour of adhesive setae)

Surface profile and chemistry of biological materials may be part of a particular function. Understanding of the correlation between surface characteristics of contacting surfaces and their biological function is an important goal of our studies (figure: SEM picture of the surface of dragonfly head arresting system)

 

Knowledge about the structure and mechanical properties of biological materials may aid in understanding the relationship between structure and function. Arthropod cuticle, reptile keratin and plant materials are three main groups of materials under study. Arthropod cuticle serves many functions. It limits body dimensions and is a basis for muscle insertions (mechanical function and function of locomotion). It is an important element in organism protection against a variety of external factors, such as mechanical stress, dry, wet, cold or hot environments. It takes part in the transport of diverse epidermal secretions, and serves as a chemical reservoir for the storage of metabolic waste products. A variety of cuticular structures are parts of mechano- and chemoreceptors. The cuticle, its coloration pattern, and chemical components are important for thermoregulation, and are often involved in diverse communication systems. Specialised cuticular protuberances may serve a variety of functions, such as oxygen retention, food grinding, body cleaning (grooming), etc..

Snake locomotion relies on the frictional properties of the skin, which can demonstrate friction maximisation, minimisation and frictional anisotropy. Wear reduction of the snake skin is related to the gradient of material properties.

Insect attachment pads evolved mainly as adaptations for efficient locomotion on plant surfaces. However, plant surfaces have a wide range of textures. They may be smooth, hairy, or covered with waxes or moist secretions. As with any integument, plant cuticle, with related structures, is a functional organ reflecting a number of environmental pressures. These pressures resulted in the particular design, ultrastructure, and chemistry of the plant surface. During the long period of co-evolution between flowering plants and insects, plants have developed not only structures attracting pollinators, but also a wide variety of structural and chemical attributes of their surface related to defence against herbivores.