Beware, the woollen clothes you wear in future may have been produced from the slaughter house waste.
A new technique creates high-quality fibers from gelatin—which can then be spun into yarn and turned into textiles, such as mittens. Gelatin consists chiefly of collagen, a main component of skin, bone, and tendons. Large quantities of collagen are found in slaughterhouse waste and can be easily made into gelatin.
That’s why Prof. Wendelin Stark and PhD student Philipp Stössel of ETH Zurich’s Functional Materials Laboratory (FML) decided to use the biomaterial for their work.
In his experiments, Stössel noticed that when he added an organic solvent (isopropyl) to a heated, aqueous gelatin solution, the protein precipitated at the bottom of the vessel. He removed the formless mass using a pipette and was able to effortlessly press an elastic, endless thread from it. This was the starting point for his unusual research work.
As part of his dissertation, Stössel developed and refined the method, which he has just recently presented in the journal Bio macro molecules. The refined method replaces the pipette with several syringe drivers in a parallel arrangement. Using an even application of pressure, the syringes push out fine endless filaments, which are guided over two Teflon-coated rolls. The rolls are kept constantly moist in an ethanol bath; this prevents the filaments from sticking together and allows them to harden quickly before they are rolled onto a conveyor belt.
Whereas natural wool fibers have tiny scales, the surface of the gelatin fibers is smooth. “As a result, they have an attractive luster,” Stössel says. Moreover, the interior of the fibers is filled with cavities, as shown by the researchers’ electron microscope images. This might also be the reason for the gelatin yarn’s good insulation, which Stössel was able to measure in comparison with a glove made of real sheep wool.
Gelatin’s major drawback is that it its water-solubility. Stössel had to greatly improve the water resistance of the gelatin yarn through various chemical processing stages.
Despite their environmental friendliness, fibers made of biopolymers from plant or animal origin remain very much a niche product. At the end of the 19th century, there were already attempts to refine proteins into textiles. For example, a patent for textiles made of gelatin was filed in 1894. After the World War II, however, the emerging synthetic fibers drove biological protein fibers swiftly and thoroughly from the market.
Over the past few years, there has been increased demand for natural fibers produced from renewable resources using environmentally friendly methods. Wool fiber in particular has experienced a renaissance in performance sportswear made of merino wool. And a few years ago, a young entrepreneur in Germany started making high-quality textiles from the milk protein casein.
