An MIT-lead team of researchers have created a new material called regenerated silk fiber (RSF) that is several times stronger than natural fiber.
The innovation was headed by McAfee Professor of Engineering Markus Buehler, postdoc Shengjie Ling, research scientist Zhao Qin, and three others at Tufts University.
Some kinds of silk produced by spiders are among the strongest materials known, pound for pound. But unlike silkworms, spiders cannot be bred to produce the fibers in useful amounts.
Various researchers, including Buehler and his collaborators, have attempted to make purely synthetic silk instead, but those efforts have not yet yielded fibers that can match the strength of the natural versions.
The researchers have now found out that the key lies in breaking down the natural silk, but not too much. The researchers have succeeded in dissolving 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.
Buehler compares this recycling of materials to tearing down an old brick house. Instead of just knocking the house down into a pile of rubble, the individual bricks are carefully separated and then used to build a new structure.
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.
According to the researchers, this process could open up a variety of possibilities for new uses.
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Such forms can be created by using the reconstituted material in a kind of 3D printing system customized for silk solution.
And 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 researchers contend that the specific properties of the fiber, including its stiffness and toughness, can be controlled as needed simply by varying the speed of the extrusion process.
Image credits and content: MIT