Spider silk is extraordinarily strong, with the strongest known type, dragline silk from Darwin's bark spider, having a tensile strength of about 1.6 GPa (gigapascals), which is comparable to or even exceeds that of high-grade alloy steel. Despite this, spider silk is much less dense than steel, making it about five times stronger than steel by weight. Additionally, it is highly elastic, capable of stretching up to five times its relaxed length without breaking, and is considered tougher than Kevlar, a well-known strong synthetic fiber.
The strength of spider silk comes from its unique protein structure, nanoscale organization, and biological synthesis at room temperature without harsh chemicals. A one-millimeter diameter cable made from Darwin's bark spider silk could theoretically support the weight of a large lioness, about 130 kg, showing how strong these fibers can be for their size.
The remarkable combination of tensile strength, elasticity, and lightweight nature makes spider silk a material of great interest for potential industrial applications, including as a replacement for synthetic fibers like Kevlar and carbon fiber.
In summary, spider silk is as strong as steel in tensile strength but is much lighter, making its strength-to-weight ratio very high, and it also possesses extraordinary toughness and elasticity.
