Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Victimless Leather points mentioned above. As with most of the TC&A projects the artists are concerned with the relationship between humans and other living systems, both natural and scientific made or manipulated. The artists wanted to make a leather-like material using living tissue, and ended up making it in the shape of a stitchless jacket. The artists based the jacket on a biodegradable polymer, coated it with 3T3 mouse cells to form connective tissue and topped it up with human bone cells in order to create a stronger skin layer. To create the victimless leather, the team needed an artificial environment where