I love Gore-Tex as a material. It's one of the few materials that has a negative Poisson ratio (when you stretch it the material expands in all directions, it d

I love Gore-Tex as a material. It's one of the few materials that has a negative Poisson ratio (when you stretch it the material expands in all directions, it doesn't narrow). My Ph.D. supervisor keeps a small sample of it to use for demonstrations to his Mechanics of Deformable Solids course. Only man-made materials can exhibit this property.