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Texcycle #2


Texcycle is a series of articles going round the textile value chain spotlighting materials, techniques and systems that can help close the loop. Following on from Raw Materials, we go into the laboratory to explore how natural polymers, microbes and DNA are being manipulated to create alternative, biodegradable manmade fibres.

Know your Fibre
Fibres, both natural and synthetic, are made up of polymers: long, repeating chains of molecules. In cotton, these are made of cellulose, a carbohydrate, while silk, wool and leather fibres are built of the proteins fibroin, keratin and collagen respectively. Synthetic polymers are man-made and mainly derived from petroleum. Furthermore, fibres can be classified as either staple or filament. Most natural fibres, such as cotton and wool, consist of shorter staple fibres of discrete lengths, whereas silk and synthetics are long, continuous filament fibres, which can also be cut up into staple fibres.

Regenerated Fibres
Cellulose is the main constituent of plant cell walls and the most abundant natural polymer on earth, however not all plant fibres are created equal. Unlike cotton, wood and bamboo pith fibres are hard and too short for traditional textile processing – but with chemical assistance the cellulose polymers can be dissolved into a viscous solution, pushed through a spinneret, and extruded into filament fibres that, once hardened, can be woven into textiles.

Rayon or viscose is the generic name given to regenerated cellulose fibres, and although biodegradable, depending on the chemicals and processes used, some varieties are more environmentally friendly than others. Tencel, a brand of lyocell by Austrian fibre producer Lenzing, is manufactured from organic, sustainably sourced wood in a closed loop system, where process water and chemical solvents are reused at a recovery rate of more than 99%.

A similar process can be used to manufacture regenerated protein fibres, aka azlon, using proteins from milk, corn, peanuts or soybeans. Both regenerated cellulose and protein fibres have been in existence for a good century, and in the last decade Finnish fibre technology company Spinnova and German startup Qmilk have developed the first patented spinning processes that turn cellulose from wood pulp and casein from excess skimmed milk into textile fibres without the need for harmful chemicals.

Lab-grown Leather
Aside no harm done to animals, lab-grown leather eliminates the need to raise livestock, thereby saving time and resources, as well as reducing greenhouse gases. Collagen is the fibre that makes up leather and is the most common protein found in mammals. Without using any animal derivatives, New York-based Modern Meadow have engineered a strain of yeast that can produce collagen through fermentation (like human insulin is synthesised for the treatment of diabetes).

When made at scale, Modern Meadow’s Zoa™ biofabricated materials can be assembled into a leather-inspired material – which, among other applications, can be poured into a mould – and can therefore do away with seams or sewing. What’s more, the process can take as little as two weeks to manufacture in the confines of a laboratory. Over in San Francisco, VitroLabs are growing BioFur pelts and leather from stem cells, while Provenance Biofabrics are looking to sculpt collagen into exotic bio-hides.

Spider Silk
One of the toughest materials of the natural world, spider silk is about five times the strength of steel by density, yet more flexible than rubber. Unlike docile silkworms however, spiders are challenging to cultivate on an industrial scale: not only do they require plenty of room to spin their webs, they are also very territorial and have a tendency to cannibalise any encroaching neighbours, as well as their own webs.

Since mammals produce milk in a way not dissimilar to how spiders produce silk, in 2001 Nexia Biotechnologies in Canada decided to splice a spider silk-spinning gene into goat DNA to create transgenic “spidergoats” that produce milk containing spider silk protein. Silkworms too have been genetically modified to create Michigan-based Kraig Biocraft LaboratoriesMonster and Dragon Silks: hybrid spider-silkworm fibres, which the US Military are incorporating into bulletproof body armour.

More recently vegan-friendly, synthetic spider silks have been developed in the form of AMSilk Biosteel (Germany), Bolt Threads Microsilk (California) and Spiber Qmonos (Japan). These recombinant spider silk proteins are produced in large quantities via fermentation in yeast and bacteria – much in the same way as Zoa bioleather. The liquid silk protein is then extracted and spun into textiles using the viscose/rayon process outlined above. Adidas, The North Face, Omega and Stella McCartney are some brands who have already started using synthetic spider silk.

Moral Fibres
From the ethics of genetic engineering to potentially hazardous sources of biotech waste, the environmental, social and economic impact of all new technologies must be carefully assessed to avoid creating new problems in the future. To dress a growing global population, textile production will need to become more efficient, and responsible biofabrication is just one of the ways this could be achieved sustainably.

Next Instalment: Eco-friendly dyeing with bacteria, ultrasound, digital printers and more.

Written by Mairi Hare as part of a collaboration between Sourcebook GmbH and Texpertise Network.


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