The complex mix of molecules that makes up fibers of natural silk, nature beats human engineering hands down.
Engineers have found they can make a material that is more than twice as stiff as its natural counterpart and can be shaped into complex structures such as meshes and lattices.
The new material is dubbed regenerated silk fiber (RSF) and could find a host of applications in commercial and biomedical settings, the researchers say.
The team has developed a way to harness the best qualities of natural silk produced by silkworms. While, processing it gets stronger and opens up a wide variety of new shapes and structures that could never form from natural silk.
The key is to break down the natural silk, but not too much. They dissolve the cocoons built by silkworms, not to the point that the material’s molecular structure breaks down but rather into an intermediate form composed of microfibrils.
These tiny, thread-like assemblies preserve some of the important hierarchical structures that give the silk its strength.
Though, silk thread and fabric are expensive. In bulk, unprocessed silkworm cocoons cost only about $5 per kilogram.
By breaking down the silk and then extruding it through a tiny opening, the researchers found they could produce a fiber twice as stiff as conventional silk and approaching the stiffness of spider drag-line silk.
This process could open up a variety of possibilities for new uses. The method also allows the researchers to shape the material in ways that could never duplicate by natural silk.
It could form into meshes, tubes, and fibers much thicker than natural silk, coils, sheets and other forms.
One advantage of the new process is that it can be carried out using conventional manufacturing technologies. So, scaling it up to commercial quantities should not be difficult. The properties of the fiber can control as needed simply by varying the speed of the extrusion process.
These reconstituted fibers very sensitive to different levels of humidity, and they can make electrically conductive by adding a thin coating of another material.