How to build regenerated silk fibres
While various companies have created artificial silk, the manmade material cannot match the natural fibre’s strength. However, by altering silk produced by silk worms, researchers at MIT have discovered they can make a material called regenerated silk fibres (RSF) that is twice as stiff as its natural counterpart, and can be shaped into complex structures such as meshes and lattices.
Spider silk is pound for pound among the strongest materials known. However, unlike silk worms, spiders cannot be bred to produce the material in useful amounts.
Rather than creating an artificial silk, the engineers at MIT developed a way to harness the best qualities of natural silk produced by silkworms, all the while making it stronger.
The team dissolved the cocoons, but not so much that the material’s molecular structure was broken down. Rather, the fibres turned into an intermediate form composed of microfibrils. These tiny, thread-like assemblies preserve some of the important hierarchical structures that give silk its strength.
The microfibrils were then extruded through a tiny opening, producing a fibre twice as stiff as conventional silk and approaching the stiffness of spider silk. The stiffness can be controlled by the speed of which the material is extruded.
This method also allows to shape the material in new ways, which cannot be duplicated by natural silk. It can be formed, for example, into meshes, tubes, coils, and many others, which can be created by using the material in a kind of 3D printing system.
While silk thread and fabric are expensive, these costs are mostly generated by the labour intensive process of unravelling the thread from the cocoon and weaving it, not the production of silk cocoons.
As silk is biocompatible, the regenerated silk fibres can be used for, for instance, medical applications, biosensors, or textiles.
Photos & GIFs: MIT