Yarn from slaughterhouse waste

Spun into yarn and wound around cardboard rolls, it scarcely looks like gelatine at all.  
Photo: Philipp Stössel, ETH Zurich

Some 70 million tonnes of fibres are traded worldwide every year. Man-made fibres manufactured from products of petroleum or natural gas account for almost two-thirds of this total. The most commonly used natural fibres are wool and cotton, but they have lost ground against synthetic fibres. Despite their environmental friendliness, fibres 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 gelatine was filed in 1894. After the Second World War, however, the emerging synthetic fibres drove biological protein fibres swiftly and thoroughly from the market.

Now Philipp Stössel, a 28-year-old PhD student at the Institute of Chemical and Bioengineering of ETH Zurich, is presenting a new method for obtaining high-quality fibres from gelatine. The method was developed in cooperation with Rudolf Hufenus and his team at Advanced Fibers Laboratory at Empa St. Gallen. Stössel was able to spin the fibres into a yarn from which textiles can be manufactured.

In his experiments, Stössel noticed that when he added an organic solvent (isopropyl) to a heated, aqueous gelatine 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 an article for the journal Biomacromolecules.

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. Using the spinning machine he developed, Stössel was able to produce 200 metres of filaments a minute. He then twisted around 1,000 individual filaments into a yarn with a hand spindle and had a glove knitted from the yarn as a showpiece.

Is it water resistant? The glove made from gelatine fibres undergoes tough tests.
Photo: Philipp Stössel, ETH Zürich

Very good insulation
Extremely fine, the individual fibres have a diameter of only 25 micrometres, roughly half the thickness of a human hair. Whereas natural wool fibres have tiny scales, the surface of the gelatine fibres is smooth. “As a result, they have an attractive luster,” Stössel says. Moreover, the interior of the fibres is filled with cavities, as shown by the researchers’ electron microscope images. This might also be the reason for the gelatine yarn’s good insulation, which Stössel was able to measure in comparison with a glove made of merino wool.

Gelatine’s major drawback is that it its water-solubility. Stössel had to greatly improve the water resistance of the gelatine yarn through various chemical processing stages. First he treated the glove with an epoxy in order to bond the gelatine components more firmly together. Next, he treated the material with formaldehyde so that it would harden better. Finally, he impregnated the yarn with lanolin, a natural wool grease, to make it supple. In the coming months, Stössel together with Empa's specialists will research how to make the gelatine fibres even more water-resistant.