Manufactured spider silk could be used for artificial tendons and ligaments, sutures, parachutes and bulletproof vests. But engineers have not managed to do what spiders do effortlessly. ... Spiders don't actually spin ("spinning" refers to the age-old art of drawing out and twisting fibers to form thread); instead, they squirt out a thick gel of silk solution. (One teaspoonful can make 10,000 webs.) They then use their hind legs as well as their body weight and gravity to elongate the gel into a fine thread. "The amazing thing nature has found is how to spin a material out of an aqueous solution and produce a fiber that doesn't re-dissolve," McKinley said. Like a cooked egg white, dry spider silk doesn't revert to its former liquid state. What started out as a water-based solution becomes impervious to water. ... While the silk stretches and dries, it forms miniscule crystalline structures that act as reinforcing agents. Engineered nanoparticles--tiny materials suspended in artificial silk--may be able to serve the same purpose.
Making the artificial silk will be hard, though -- it's not like it grows on trees.