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Three years ago, Kaplan stopped by Omenetto’s office carrying a clear silk film his group had engineered. Up to that point the two scientists had always gotten along well, and each appreciated the other’s exuberant scientific passion, but collaborating on a research project had seemed unlikely. They came from very different backgrounds. While Kaplan has always been a bioengineer, Omenetto’s field is optics, the branch of physics concerned with the behavior and properties of light. He has made a career studying how light from high-powered lasers interacts with optical fibers and photonic crystals. Always, his goal has been to harness the unfamiliar effects such materials have on light, and put these effects to work for precision imaging and sensing.
But as Omenetto observed the hard, clear, pliant silk in Kaplan’s grasp that day, he was shocked. “It was very transparent, and looked nothing like the silk that I was used to seeing,” recalled Omenetto. “At that moment I realized I could make optical devices out of it.” He has since used silk to fabricate a multitude of devices and components, some with nano-scale structures imprinted on their surfaces, others embedded with electronics, some coated with strange substances known as metamaterials. Unlike similar devices made from glass or metal, the silk ones can be implanted in the body, allowing us, in Omenetto’s words, “to interface the biotic and abiotic realms.” With silk optics, a new field is being established: one in which optical detectors, monitors, biochemical sensors, and metamaterials can be implanted directly in the body, to send and receive information to the outside world.
Omenetto and Dr. John Rogers at the University of Illinois have already collaborated to create silk sensors that can be inserted under the skin to optically monitor glucose levels in the blood. Embedded with microscopic antennas, the sensors will eventually have the capacity to electronically transmit precise information about the body from the inside out—for example, via a text message.
They are also attempting to create a silk gel infused with gold nanoparticles, small spheres that resonate when stimulated with green light and consequently heat up to extremely high temperatures. This gel can be injected into the body in the region of a tumor or growth. Illuminated from outside, through skin and muscle, with a simple green laser pointer, the resonance of the nanoparticles suspended throughout the biodegradable silk gel would roast the tumor.
In Omenetto’s eyes, not all the future uses of silk will be biomedical or high-tech. Bulk production is ready and waiting for the right capital investor to come along and commercialize it. As soon as silk is cheaply available, Omenetto foresees that it could replace petroleum-derived plastic worldwide. Water bottles, grocery bags, toys, ball-point pens: all such things, he believes, could eventually be made of biodegradable silk instead of synthetic polymers. Manufacturing of such products would be entirely green and water-based, and their lifetime could be varied to suit their use. Omenetto is an optimist, to be sure, but he is also a man of action. After hearing him talk, and surveying all that he has accomplished so far, one begins to think that perhaps the days of landscapes ravaged by discarded, decay-resistant plastic trash really are numbered.
The grad student who takes care of the optics lab’s silkworms, Jason Bressner, was recently knocking around in the lab when he noticed a Petri dish with its lid ajar. Silkworms, he explained, don’t really like spinning cocoons in such confined spaces, and some of them are strong enough to push their lids off and amble out. He usually finds them spinning silk somewhere nearby, but this particular specimen was nowhere to be found. Bressner suspected he would come across it eventually, in moth form, fluttering about the lab in search of a mate, but when I asked him later he said it never turned up. I liked to think of this brave silkworm getting away—one of only a few across thousands of generations to successfully escape human captivity. It occurred to me that our days of ravaging Bombyx mori silkworms may be numbered too. Now that we possess their DNA, we don’t really need to exploit them anymore. The hundreds of billions laboring on farms all over the world—soon, maybe, they can all go free.
Originally published September 17, 2010
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