Sand fish effect
The sandfish effect is the term used to describe the abrasion and friction-reducing characteristics of the shell of some desert-dwelling reptiles . So far it is known from three genera : The sand fish ( Scincus ), the sand sneaks ( Sphenops ) and the real sand boas ( Eryx ). It is believed that these reptiles each developed the special structure of the skin convergent as an adaptation to the way of life burrowing in the desert sand.
The scales are like other reptiles from keratin formed which have a particular microstructure. Under the scanning electron microscope , the scales show transverse threshold structures with a diameter and height of about one micrometer at intervals of about 8 micrometers. In the case of back scales, thorn-like projections (“nano-spikes”, 40 nm ) can also be seen on the threshold structures. The diameter of an average grain of sand corresponds to the size of 38 sleepers. They act as “brushes” which strip off clay mineral layers that are firmly attached to the grains of sand . This significantly reduces the coefficient of friction . This also prevents the clay minerals from settling on the skin. In one experiment, the clay minerals could be removed from the sleepers by blowing lightly or using a soft brush.
The structure of the scales also prevents their wear and tear.
Because of these features, the reptiles can move quickly in the sand, similar to swimming in water. Tests have shown that the scales of these reptiles are less abrasion and frictionless than conventional materials such as steel.
The sand fish effect is a current research area in bionics .
See also
literature
- Ingo Rechenberg and others: Tribology in dune sand - sand fish, sand boa and sand creep as a model for reducing friction and wear. Final report, BMBF grant number 0311967A, duration February 1, 2006 to March 31, 2009, (PDF file; 3.32 MB)