When most people hear the word "silk," they are likely to envision shimmering, lavish fabrics worn by royalty and elites; they are not, however, likely to think of biomedical sensors and practical scientific metamaterials. But for a team of researchers at Tufts' School of Engineering and Boston University, this assumption could not be less accurate.
For the past several years, Professors David Kaplan and Fiorenzo Omenetto of the biomedical engineering department have been exploring uses of this ancient material that stretches far beyond the realm of cloaks and nightgowns. Both professors, along with other researchers from Tufts and Boston University, have discovered new uses for silk that could have wide implications in the medical world.
"Three years ago, roughly, we started playing with silk and … reinventing silk as a technological material," Omenetto said. "It's turning into something that interfaces with electronics that interfaces with the body [and] interfaces with high−tech applications."
Through their research, the team has found ways to restructure silk and embed it with artificial electromagnetic composites known as metamaterials. These metamaterials are essentially an array of tiny antennae — typically made up of conductive metals such as gold — that can be used as biosensors and biodetectors. Omenetto explained that because silk can be restructured in a way that allows it to dissolve in the body, it can safely be implanted in human tissue, opening up a vast array of possibilities for use in the medical sphere. And because silk is made from natural materials, it is a far more sustainable product than materials that have been used in the past, such as plastics.
"It's becoming our real materials playground to create new devices that are green, sustainable, biological, implantable, edible," Omenetto said.
Some of the uses include the ability to implant sensors in the body to detect abnormalities and examine bodily processes, such as concussions, according to senior Tom Valentin, a student researcher in the lab. Another product of the research could include an implantable glucose sensor for those suffering from diabetes. The sensor would react as glucose levels change in the body and then communicate that change to an external sensor or device. Basically, patients could avoid having to test themselves with needles.
The research of silk, however, is not limited to its uses with metamaterials. Kaplan explained that because of the material's strength, flexibility and ease of manipulation, many other biomedical and practical uses have been discovered through the research. The advancements the materials could effect range from new kinds of medical adhesives to lighter, more practical bullet−proof vests, he said.
"The fact that we've been able to build a platform of opportunities … that open up new medical applications as well as environmental applications is very exciting," Kaplan said. "We've already seen the commercial interest in everything from ligaments and things like that to drug delivery in silk−based biomedical materials."
Some of Valentin's work has focused specifically on the use of silk to administer antibiotics into the body.
"You can dissolve antibiotics or a whole slew of different chemicals … into silk, and then you can implant that in the body," Valentin said.
One potential use that has received a great deal of attention in the past few months has been the potential for silk−based metamaterials to render certain objects invisible. Omenetto explained that certain metamaterials can be engineered to either absorb or reflect certain light waves, and that this technology can manipulate the way objects are viewed.
"You design the little [antennae] and how they're arranged so that they either absorb a certain type of wave perfectly or they reflect a certain type of wave perfectly," Omenetto said.
He continued that by designing the antennae to absorb and reflect certain colors and waves, one could potentially make an object appear to be completely reflective or transparent.
"That's the intellectual exercise that a lot [of] people have done, saying, ‘Well if I can engineer responses, then I can engineer this fantastic material that will be perfectly reflective at all wavelengths at all angles,'" he said.
But while the fantastical idea of using gold and silk to render things and people invisible sounds exciting and appealing, Omenetto explained that the potential for this technology to be used on a widespread basis is slim, noting the great difference between making small materials transparent in the biomedical sphere and creating a full−on invisibility cloak.
"The gap between the two is just enormous," he said.
