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Fashionista Worms and Goats
Posted on July 29th, 2016 by Dr. Sina Ebnesajjad in New Materials & Applications
The image below shows a dress from Valentino’s Resort ’16 collection described as “bohemian exoticism with the volatile glamour of a garden party. This romantic and whimsical gown is cut from wispy silk-organza with long sleeves and a floor-sweeping hem.” (Source: www.net-a-porter.com) Just in case you are curious the dress is on sale for just under $20,000.
If not the beauty of the dress, the price alone makes it worthy of a fashionista! A term invented by Stephen Fried’s in a 1993 biography of supermodel Gia Carangi, as a way to refer to the entourage surrounding supermodels at a photo shoot.
Silk is Nature’s very own homespun wonder material. Silk fibers have several outstanding properties unmatched by even the most advanced synthetic polymers:
- Because of its natural protein structure, silk is the most hypoallergenic of all fabrics.
- An all-climate fabric, silk is warm and cozy in winter and comfortably cool when temperatures rise. Its natural temperature-regulating properties give silk this paradoxical ability to cool and warm simultaneously. Silk garments thus outperform other fabrics in both summer and winter. Silk worn as a second layer warms without being bulky.
- Silk is highly absorbent and dries quickly. It can absorb up to 30% of its weight in moisture without feeling damp. Silk will absorb perspiration while letting your skin breathe.
- In spite of its delicate appearance, silk is relatively robust and its smooth surface resists soil and odors well.
- While silk abrasion resistance is moderate, it is the strongest natural fiber and, surprisingly, it easily competes with steel yarn in tensile strength.
- Silk takes color well, washes easily, and is easy to work with in spinning, weaving, knitting, and sewing.
- Silk blends well with other animal and vegetable fibers.
People have attempted to produce artificial silk for centuries. Examples include acetate fiber derived from the cellulose of tree pulp dating back to the late 19th and early 20th century. Acetate fiber, known as Rayon, has some of the properties of silk but it is mechanically weak and susceptible to abrasion. Efforts to make synthetic polymer fibers matching silk have all failed. Silk has simply too many desirable properties that have proven virtually impossible in a single man made fiber.
Human intellect has been no match for a small white worm feeding on mulberry leaves. It spews out threads from tiny holes in its jaws to spin a cocoon to house its eggs. The entire process takes a mere 72 hours, during which time a worm produces between 500-1200 silken threads. At that point the silkworm farmer harvests the cocoons, this is followed by a process to recover the silk threads that are eventually made into fabric.
Silk fiber is secreted by several species of insects in order to build protective structures for their eggs. It is tough to make silk in bulk because the worms are hard to scale. The worms work at their own pace indifferent to the productivity needs of society. This fashionista can’t be made to rush.
What about the goat?
It is all about proteins. Fibroin is an insoluble protein present in silk created by the silkworm. The super strength of spider webs and other silk secreting insects are made of fibroin. Raw silk contains of two proteins, sericin and fibroin. A glue-like layer of sericin coats two single filaments of fibroin, forming a silk thread called brins. [Source: O. Hakimi et al., “Spider and mulberry silkworm silks as compatible biomaterials”, Composites Part B: Engineering, vol. 38 (3), pp. 324—337]. Prof Randy Lewis at the Utah State University genetically modified 30 goats so that they would produce fibroin in their milk. He’s engineered these goats specifically to make silk; all he needs to do is treat the proteins—clean them, dry them, and add a few solvents—and he has a silk almost identical to that created by worms and spiders.
Japanese startup, Spiber, credited on the Disrupt 100 list, has also been researching production of fibroin in milk. They have decoded the gene responsible for the production of fibroin in spiders. Spiber is aiming at commercial production of goat-based fibroin.
Let’s wait and see if silk production from goats will scale better than silk worms and spiders.
All opinions shared in this post are the author’s own.
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Dr. Sina Ebnesajjad
President at FluoroConsultants Group, LLC