The lobster shell is quite difficult. But the transparent material on the underside of his tail can be even more incredible: Laboratory tests show that the thin, stretchable substance is as strong as the tire used to make tires. the underside of the crustacean tail contains chitin, a fibrous material found in the exoskeletons of many insects and crustaceans. But team tests have shown that the substance is about 90% water, which gives the material elasticity. There is also a plywood layout of microscopic layers, each of which with chitin fibers that run mostly in one direction, but with those in the adjacent layers operating in slightly different orientations. The same way of arranging helps ensure the strength of plywood in several directions that one layer of wood does not possess, researchers note. , reports the team in the forthcoming issue of Acta Biomaterialia . Stretching the material makes it even harder, they note. Generally, the material is rigid as those used to make garden hoses, tires and conveyor belts. Another advantage of the layering of the membrane: Cuts or slits that penetrate only a few outer layers usually do not spread in intact layers, making the material "error tolerant". joints like elbows and knees, in armor or hard suits, suggest the researchers.