teaching
Evolutionary Biomaterials Group

 

Structure of biological materials is studied by a variety of microscopical methods, such as light microscopy, scanning and transmission electron microscopy combined with different preparation techniques (critical point drying, freeze-fracture, freezing-substitution (figure: TEM picture of the longitudinal section of a fly seta)

Frictional and adhesive forces between surfaces are measured on global and local scales. On the global scale, centrifugal force tester, load-cell force transducers, and microforce testers are applied. On the local scale, atomic force microscopy and nanoindentation are used (figure: combination of the double-leaf glass spring and fiber-optical sensor used for adhesion measurements)

Information about surface profile and physico-chemical properties of biological surfaces and various artificial materials is necessary for understanding frictional and adhesive behaviour of contacting pairs. Contact angle measurements, white-light interferometry, profilometry, and various chemical treatments are used (figure: 3D profile of the carnivorous plant surface obtained by white-light interferometry)

Movements in biological systems are analysed by regular and high-speed video recordings. Spatial orientations of joint axes are analysed by 3D measurements with the aid of measuring microscopy and software allowing inverse kinematics analysis (figure: video frame of the second and third tarsi of a beetle walking upside down on a glass surface)

 

We perform a quantitative analysis of surface structures of different biological systems using various microscopy and profilometric techniques. Emphasis is put on light microscopy, transmission and scanning electron microscopy, atomic force microscopy including different preparation methods using freezing techniques, critical point drying, and dental wax replication.

Measurements of local mechanical properties include testing of contact formation and viscoelastic response on very small amounts of material by nanoindentation and AFM techniques. These investigations reveal the deformation mechanisms, including time-dependence, anisotropy and energy-loss behaviour.

Measurements of global mechanical properties and attachment/detachment performance include normal and shear testing by micro-force testing of attachment/detachment. These studies probe the behaviour of the entire biological system or artificial sample.

To understand the behaviour of biological structures and artificial prototypes the visualisation of fast movements is often required. For this purpose a motion system has to be recorded using high-speed cameras, mounted on a binocular microscope, then digitised and analysed.