As manufacturers respond to consumer interest in eco-friendly products and seek ways to soften the impact of rising oil prices, organic composites are on the upswing in terms of diversity and quantity. Enticed by incentives, such as the USDA bio-preferred program as well as dreams of super-composite applica- tions, visionaries in the composite industry are incorpo- rating a wide range of bio materials — from crop waste to feathers, and even genetically engineered superfibers like spider silk.
The allure of arachnid silk spurs research
The idea of spider silk may conjure images of Spider Man, but the promise of stronger, more elastic fibers is driving research into genetically engineered composites. Randy Lewis, a professor of biology and spider-silk re- search with the Utah Science Technology and Research initiative (USTAR), in Salt Lake City, says “the reason there’s a lot of interest in spider silk is that one of the silks a spider produces has a tensile strength greater than Kevlar materials and elasticity greater than nylon.” USTAR has developed alternative methods to produce spider silk, he says.
The Orb-weaver spider produces different kinds of silk with various mechanical properties, Lewis says. “The silk itself is a protein, so we’ve cloned the genes for each of the proteins that make up the different spider silks.” Researchers then create new genes based on those proteins and place them in bacteria, silk worms and goats, using those genetic pathways to produce engineered spider silk, he says.
“We then purified a protein, either from the bacteria, or, in the case of goats, they produced the spider-silk protein in the milk, and in the case of plants, they produced it in the leaves. So, we actually had to extract the protein, then spin fibers,” says Lewis.
With the silk worms, Lewis says researchers used a cloning kit to combine proteins, enabling the silk worms to spin the cocoons themselves to get fibers that combined super silk and spider silk.
Though still in the research phase, Lewis says researchers have already generated fibers with widely differing mechanical properties, depending upon which spider silk proteins are used. “We have ones that have very, very high elongations; we have ones that have very low elongations; we have ones that have high-tensile strengths and we have ones that have much more moderate tensile strengths,” Lewis says.
“So far scientists have not yet been able to precisely match what spiders do with their very best silk,” Lewis says. “We’re about half way there and we are still, in some cases, developing ones that are better than Kevlar materials for specific composite applications.”
So far a lot of focus has been within medical applica-tions, such as artificial ligaments and tendons, and compressive bandages, but there are other possible outcomes of the research,” Lewis says. The team’s work has just begun moving in the direction of composites. They are meeting with various executives at commercial enterprises, who are interested in the possibilities for super fabrics within composite applications.
We’ve made composites with a bio-plastic that another group in Utah is producing,” he says. “We’re making composites of polyhydroxyuterine, and polyhydroxyvalorate (bacterially produced plastic), combined with our spider silk and strand fibers.” Scientists cloned the first spider silk gene 20 years ago, says Lewis. “We’ve been beating on this for a very long time, and we’re just now at the point where commercialization is a probability, not a possibility.”
Lewis says his team’s research effort will lead to new materials within two years and depending on how the silkworm work goes, he expects to have testing underway for a variety of different purposes in a year to 18 months. He is convinced that a number of different materials based on spider silk in some form or another will be commercially available within a decade.