Spiders sprayed with water containing carbon nanotubes and graphene flakes have produced the toughest fibers ever measured, say materials scientists. Spider silk is one of the more extraordinary materials known to science. The protein fiber, spun by spiders to make webs, is stronger than almost anything that humans can make. The dragline silk spiders use to make a web’s outer rim and spokes is amazing stuff. It matches high-grade alloy steel for tensile strength but is about a sixth as dense. It is also highly ductile, sometimes capable of stretching to five times its length. This combination of strength and...