The Future of Silk – Scientific American Blog Network


On March 16, 1897, in a dusty Chicago square, an expert shot walked eight paces, raised his revolver and fired at the chest of the Reverend Casimir Zeglen. A 35-year-old priest then serving at St. Stanislaus’ Roman Catholic Church in the city, Zeglen was hit squarely by the bullets and fell to the ground. Moments later, the crowd that had gathered cheered uproariously as Zeglen got back up to his feet, raised his hands, and announced that he was unharmed.

The event was designed neither as an execution nor as theater. Zeglen had himself hired the marksman to test an invention he would go on to patent as the world’s first “soft armor.” Zeglen had worked out the ideal design by experimenting with the weave, direction and layering of a soft, fine, natural cloth. His fabric of choice—and the one that would save his life—was silk. Zeglen’s bulletproof vest would be marketed to royalty and presidents, officials who were the primary targets of anarchists and revolutionaries and to police officers and detectives whose lives were at risk every day in the 19th-century world of violence and anarchy. By the 1900s they were sold across the world, and had been bought by a number of heads of state.

The idea had occurred to the priest around four years earlier, when the news of the assassination of Chicago’s mayor on the doorstep of his house was reported, to the horror of everyday Americans. Particularly sensitive to violence, Zeglen seemed more shocked than others—horrified enough to wonder if there wasn’t a way to create clothing so thin that when worn would be unknown to the attacker, but so strong that it could stop the penetration of an assassin’s bullet (or blade), even at close range.

It seemed an almost unreasonable ask, but Zeglen’s silken body armor did succeed, as he had hoped, and went on to be worn by statesmen and dignitaries. Unfortunately, it became a victim of its own success. Assassins who knew of the device were able to circumvent it, and its failings became as infamous as its successes were celebrated.

The most consequential of the former was the 1914 assassination of Archduke Franz Ferdinand, heir presumptive to the Austro-Hungarian throne, and his wife Sophie, Duchess of Hohenberg. Its failure intimated a story of treason and palace intrigue that formed a key catalyst in the chain of events that led to World War I. Within a month of their deaths, Austria-Serbia and Hungary were at war, and the rest of Europe followed shortly thereafter. Shot from a pistol at close range by a slight and sickly nineteen-year-old called Gavrilo Princip, a member of a Yugoslavist organization seeking an end to Austro-Hungarian rule in Bosnia and Herzegovina, the bullet hit Ferdinand’s unprotected neck and then his jugular vein, finally lodging in the Archduke’s spine.

In the immediate aftermath, the out-of-date cyanide capsule Princip carried failed him, and so he went on to die of tuberculosis in jail. Newspapers claimed that the fact that the Archduke was hit in his neck while wearing Zeglen’s bulletproof vest on his body was proof that Princip had been in contact with an insider, and had known about the armor underneath his uniform, so that the shot was aimed instead at his neck; or alternatively, it may have been that Ferdinand was not wearing his armor at all that fateful day—again, information given, it would seem, from sources inside the palace.

Zeglen’s own aims, of course, were sincere in a time where, politically, much was at stake. In 2014 the British Royal Armories had replicas of Zeglen’s vests made to the original patent specification in order to test them with ammunition and weapons similar to the 1910 Browning semiautomatic pistol fired by Princip. They reported that, just as Zeglen had claimed, the silken armor did indeed have bullet-stopping capabilities. It is known that Casimir Zeglen had long admired the work of German inventor, Heinrich Dowe, who had also worked on the creation of bulletproof vests; but ultimately, it is unclear where Zeglen himself had taken his inspiration for his own remarkable invention.

He began experimenting on bulletproof cloth from around the age of twenty, and had trialled steel shavings, moss and even hair. What is clear is that the idea he settled on—of using silk—had by then long been employed specifically for this purpose, though never in the U.S. It was true that reports of serendipitous cases had been made public, by that time.

For example, about a decade earlier, a Dr. George E. Goodfellow of Arizona had reported that on three occasions he had become aware of, and even assisted in medical interventions in the aftermath of revolver duels. In these, each would-be victim had survived shots to the chest because of the presence of a silk handkerchief, folded a few times and held in a breast pocket. It would prove enough to stop the bullet from even penetrating the skin.

But around a thousand years before these men were inadvertently saved by silk in their new world misadventures, clothes designed for 6th– and 7th-century Chinese military officers had already been quite intentionally quilted with silks as protection against puncture wounds and cuts. The later Japanese kikou armor (which the Chinese innovation gave rise to) would eventually have metal plates sewn on top to create a composite body armor that was both flexible and hard. Such armor remained in use until the 1870s, longer than the similar European brigandine bodice, sewn with several layers of silk cloth riveted with metal scales or plates.

In Russia and in England, soft body armor was worn during the 17th-century “conspiracy of papists” riots. Called “fashionable” in contemporary reports, it comprised both a “vest and trousers made of quilted layers of silk fabric which were sewn together so tightly and were so thick that the fabric was resistant to both a bullet and a blade.”

But even unlayered, unquilted silk fabric, stripped to its threads, threads to their strands, and strands to their constituent proteins have been in use in silk’s most raw form to heal or to protect. The thin vests of the lightest silk worn by Genghis Khan’s Mongolian armies were designed to keep armor lightweight, and the soldiers on horseback who wore them nimble. But silk also served to trap flying arrows superficially in a wound, seal the wound, and allow projectiles to be removed without excessive trauma to the injured.

For a similar reason, spider webs were applied as wound dressings in Greek and Roman times (and even as nets for fishing) and in ancient Scythia, Greece and India, its threads were used to suture wounds without irritation to the body. Today silk sutures are still in use, mostly in eye and lip surgery and for some skin wounds, because of their excellent handling and tying capabilities.

Silk, after all, is also a protein, not unlike collagen, keratin and elastin, which are all important components of human skin, hair and the connective tissues in our bodies. Structurally, silk is a twin thread of the protein fibroin, coated by a sticky layer formed of sericin: a protein that among other things resists oxidation, is anti-bacterial and is UV-resistant. Made of just protein and water, silk is also finer and stronger than Kevlar—a synthetic, heat-resistant fiber developed by Stephanie Kwolek at DuPont in 1965, and used for bulletproof clothing since the 1980s (although such garments are called “bullet-resistant” these days).

Though most celebrated for its use in clothing, for all of these reasons, silk has also had an historic importance in the healing and protection of the body that has been at least 5,000 years in the making. As the strongest material that exists in nature, with a little imagination and the advent of new technologies and rapid developments in genetics, 3-D printing, materials science and electronics, the remarkable qualities of silk are set to create new cutting-edge applications—as diverse as data-collecting sports shoes to regenerative medicine, from climate change technologies to space exploration.

The Future of Silk

Around five miles northwest of the city of Boston is an outpost of Tufts University, a deceptively dull-looking high-rise office building divided from a sea of Wedgewood-blue wood-framed New England Victorian houses by an immense multistory car park. Tucked away near a freight elevator along the clinical corridors of an upper floor is a solid black door, plain except for a stylized logo that reads simply: silklab. Inside is an impressive suite of laboratories filled with high-tech machinery: nanomaterials, 3-D printers, electronics, optics, sensing and biological interfaces. Its walls display a range of products developed by its scientists.

Some creations are still too secret to photograph; others, encased for display like museum exhibits: bio-inks, wearable sensors, smart fabrics, mysterious vials of materials that look perhaps like rubber but with the strength of high-tensile engineering steel, biodegradable architecture, a skull that looks like it was made of sponge, prism-like light-reflecting mirrors, and transparent, iridescent films.

Now run by Italian physicist and laser expert Fiorenzo Omenetto, who in 2010—named by Fortune magazine as one of its 50 smartest people in tech—silklab stands as the apogee of decades of intensive and immensely creative research. As with many inventions, it was a throwaway conversation in the lab corridors that led to the discovery that silk could bring technology and biology together in entirely new ways. That conversation had been with a senior American scientist called David Kaplan, a biomedical engineer. Kaplan was holding a small piece of silk, which was meant to become a scaffold to be used to rebuild a human cornea.

But Kaplan was concerned that it didn’t have great permeability, and asked Omenetto if laser could be used to burn some tiny holes in this silk’s surface. In our eyes, corneas can have no blood vessels, because, in order for us to see clearly, they need to stay transparent. But they also need to stay alive, and that requires them to be permeable enough to absorb oxygen, nutrients from our tears, and other substance, while rejecting dust and bacteria. An artificial, implanted silk cornea would also need to be porous enough to allow our own cells to go in and regrow, to use the shape of the silk as a scaffold, or mold, and for people with corneal damage, allow them to use this to regrow a new one with their own cells for themselves.

Omenetto says he shone the laser on the film of silk from Kaplan, but he could not see the laser light, “which might have been just dumb luck,” he recounted, “but to me it meant that the material was optically sensational.” To nonphysicists, that translates as the silk film having near-perfect transparency—superior to anything made of glass, or indeed any synthetic material available. More broadly, this phenomenon presented a resolution to a quest for a material that could be implanted into the body without rejection, material that could encourage the body to repair itself, and then disintegrate when told to, as if it had never been there at all.

In the 1990s, when the new silk research all began, David Kaplan had been studying spider and silkworm silk at the U.S. Army Natick research and development labs. As his research progressed, he moved to Tufts University, and decided to focus on silk that silkworms had spun out of protein and water, and work backwards, taking the silk threads back into the liquid silk, as it was in the glands of the insects.

This liquid, when exuded from the body of the worm, normally becomes solid on contact with air. Kaplan’s idea was to work in the opposite direction. If he could get hold of the silk fluid itself, he could mold it into whatever shape he needed, and make completely new kinds of silk materials never before seen.

Kaplan, and later with Omenetto, thought that for a number of reasons this re-engineered material could possibly make replacements for cartilage and bone, packages for safely delivering medications deep into the body, artificial blood vessels for the repair of the heart and other organs, and dissolvable nuts, gears and bolts that could be implanted into the body for surgical repair.

By doing it differently from the way silkworms do it—by changing the way silk protein is processed from water—they could also create new transparent materials of natural protein that could be molded into tiny needles that cause no irritation to the skin; flexible and biodegradable implantable electronics that record our brain signals; edible sensors we could safely consume to track our fitness or the nutritional quality of our food; as a material to preserve and stabilize vaccines or antibiotics so that they can be safely transported in developing countries without refrigeration; as adhesives or reflector tapes; as data stores that allow credit-card-size devices that could hold as much information as CDs or holograms; natural optic fibers to create a new generation of technologies that will conduct light as information; or even to create “silk plastic” cups or bags; or silk electronics—a perfectly degradable antidote to plastic, as well as to the curse of electronic waste.

With enough imagination, the potential seemed almost limitless.Though Kaplan and Omenetto chose to work with the silk of silk moths, and particularly that of Bombyx mori, across the Atlantic another laboratory has persisted with manipulating not just wild moth silks, but also that of the uncooperative spider. Leading the Oxford Silk Group at the University of Oxford, professor Fritz Vollrath has been captivated by research on the architecture and engineering of spiders’ webs— as they have strength and an adaptability beyond anything Bombyx mori could produce.

As with David Kaplan, Vollrath too learns from silk to improve medicine. His company has, for example, designed the Spidrex nerve conduit capable of directing regeneration of a severed nerve; they have also used his spider-based silk materials to repair cartilage (currently in clinical trials), and create a vascular graft for haemodialysis, superior to currently used synthetic grafts that malfunction within one year and fail within two.

Whether from spiders or from worms, by learning from nature, Omenetto sees what he calls infinite scalable technology that we haven’t yet harnessed. Among materials from nature, including the natural nanotechnology used by plants his lab now studies, silk is central to a range of future technologies. Using this to reinvent electronic-human interfaces that can sense what is going on in the body is set to be the next big thing. “The fact that we start from a naturally based material drives us to put tech where tech normally doesn’t go,” he says. “It really brings biology and technology together.”

Omenetto is by no means convinced that a “singularity” is coming—the ultimate, currently science-fictional merging of our bodies with technology that some claim is not far from becoming scientific fact. But it is something he does think about. With a material as natural and implantable as silk, and one that can be seamlessly embedded with gold electronics or sensors that interact seamlessly with the body, we could well be one step nearer to such a future—both dystopian and utopian. “What if your phone was part of your body? … Or you could dip silk into a substance x or y and weave it, and when you wear it, it can tell you whether you are about to have a stroke?”

Silk is also dissolvable, and its self-destruction can be made to happen at predetermined times. This trait means, for example, that detectors using silk could be sent into our bloodstreams. Those electronics could pick up on how much oxygen or carbon dioxide or other substances there are in our blood. And what is in our blood and in our bodies, then becomes data—data that can be transmitted out to, for example, somebody’s mobile phone.

Whether this takes us toward a truly cyborg future or not, much of silklab‘s research is already becoming reality. It has attracted companies that have now produced a number of their silk innovations, from temperature-stabilized vaccines that have no need of refrigeration (better in developing countries or emergency health settings and for the environment); to Silk Voice® injectable silk, recently approved by the U.S. Food and Drug Administration for the repair of damaged vocal cords, but which can also be used as a filler for aesthetic cosmetic surgeries. They have also used silk to stabilize penicillin for many months, as they have also done for a chemotherapy drug that has remained stable (and fully functional) at the Mayo Clinic for the last seven years.

Perhaps surprisingly, it is not so much the medical potential of silk that excites Omenetto. Like Vollrath, who despite his important medical applications is becoming increasingly interested in the use of his silk in sustainable industries with significant socioeconomic potential in developing countries, Omenetto is deeply engaged in silk applications he considers has broader and immense global importance.

In the summer of 2012, on a mulberry farm in Kampot, Cambodia, Omenetto had been working with a pilot-fund project conceived by the United Nations Educational, Scientific and Cultural Organization (UNESCO) to plant mulberry trees and revive silk weaving to improve livelihoods in the country. In the 12th century, Cambodia had been part of an empire which encompassed a large part of Vietnam, Laos and Thailand, and which itself became a major center whose trading routes were connected by the “ocean silk road” between South India and China.

In the aftermath of Cambodia’s civil war in the 1970, however, little information relevant to its textile tradition remained, and almost all of the silk yarn it subsequently used for textile production began to be imported from Vietnam. Silk-making survived only in a few remote weaving villages, and over the last quarter of a century, villagers resumed raising indigenous silkworms that produce yellow silk cocoons, and from it creating a golden-hued yarn from them.

Largely, though, the country’s silk traditions were on the verge of dying out. The UN’s drive to repurpose farms for silk allowed Omenetto’s scientists to work with these cottage industries, in which local people were able to play a role in the process of Tufts’ research and innovations with silk. The materials sourced at fair-trade prices from Kampot would make the kind of green high-tech products that would then be reincorporated into their local environment.

The vision was that the people there, having produced silk, that was used, for example, to stabilize medicines or foods, could be used right there in an environment where medical care was difficult to access and food and medicines hard to preserve. This work may not even necessitate the planting of mulberry trees for Bombyx mori silk. 

A company born out of the Oxford Silk Group has also been working on unravelling wild silks, something that has previously proved challenging. This is important, as out of more than 4000 species of silk moth that are found in every part of the world, with the exception only of Antarctica, a mere handful are currently used for commercial silk production. Being able to manipulate the silk of wild moths just as Bombyx mori silk is will allow local use of a range of new silk-based materials with greater strength and superior properties to its domestic relative.

 It is in this kind of bigger-picture problem solving that silk-manipulating scientists see the real potential of the future of silk, what Omenetto describes as more profound social implications than anything that happens in American or European curiosity-driven research bubbles. Working with Cambridge Crops in the U.S., for example, silklab innovations have been applied to create edible food coatings that minimize the global food waste (that currently accounts for over $1 trillion of lost revenue), limit harmful greenhouse gas emissions and water waste caused by the food supply chain, and reduce our reliance on nonbiodegradable plastic packaging. On the ground, in developing countries, some of their work in collaboration with farmers has already stabilized cassava crops.

In a world facing the effects of climate change, population migration and habitability, the vision is that a new silk industry, or toolkits based on silk, has the potential to give access to education, ideas of new approaches to materials and new applications for technologies.

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Originally posted by: Aarathi Prasad


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