Silk may be strong, elastic and biodegradable, but unfortunately it's also expensive – that's because it has to be meticulously harvested from silkworms. With that in mind, Swedish and German scientists set out to produce lower-cost artificial silk. They've already succeeded in producing small quantities, using whey protein.
Led by Dr. Christofer Lendel and Dr. Fredrik Lundell, researchers from Sweden's Royal Institute of Technology (KTH) started out by applying heat and adding acid to a solution of cow milk-derived whey. This caused it to form into nanofibrils, which are essentially tiny strands of protein. The higher the concentration of whey protein in the solution, the shorter and thinner the strands.
In a process known as hydrodynamic focussing, a carrier liquid containing the nanofibrils was then pumped through a small tube. When streams of water entered that tube perpendicularly from either side, the nanofibrils were squeezed together between them (see the illustration at the top of the page). As a result, they stuck together to form one silk-like fiber.
Using X-ray technology from Germany's Deutsches Elektronen-Synchrotron (DESY), the scientists made an interesting discovery – the short and thin nanofibrils actually produced stronger fibers than their long and thick counterparts. This is because the shorter nanofibrils are curved in shape, allowing them to lock together better.
So far, the team has managed to produce artificial silk fibers approximately 5 mm long. Now that the process is understood, however, there are hopes that longer, higher-quality fibers could be produced. It's also possible that their characteristics could be tweaked, allowing them to be tailored toward specific applications.