Researchers at Tufts University's School of Engineering have developed a new bioinspired technique that transforms silk protein into complex materials that are easily programmable at the nano-, micro- and macro-scales as well as ultralight and robust. Among the varied structures generated was a web of silk nano fibers able to withstand a load 4,000 times its own weight.
The Tufts researchers generated controllable, multi-scale materials that could be readily engineered with dopant agents. With the new technique, centimeter-scale silicone molds were patterned with micro-scale features no thicker than a human hair. An aqueous fibroin protein gel derived from silkworm cocoons was injected into the molds and then mechanically stressed by contraction of the gel in the presence of water and ethanol and/or physical deformation of the entire mold. As the system dried, the silk protein's structure naturally transformed to a more robust beta-sheet crystal. The material's final shape and mechanical properties were precisely engineered by controlling the micro-scale mold pattern, gel contraction, mold deformation and silk dehydration.
In some of the experiments the Tufts researchers doped the silk gel with gold nanoparticles which were able to transport heat when exposed to light.
In contrast to structurally dense webs spun by spiders, the Tuft’s web structure is aerated, porous and ultra-light while also robust to human touch, which may enable every-day applications in the future.