According to scientists, artificial electromagnetic composites known as metamaterials have many promises for the future, thanks to their highly conducting metal structures that “respond to electromagnetic waves in ways that atoms in natural materials do not.” So says the press release at Tufts, where a group of investigators together with colleagues from Boston University were able to marry gold-based metamaterial structures directly to pre-made silk films. The result? An advanced material that has a strong resonant electromagnetic response at THz frequencies, or as Tufts says “the frequency where many chemical and biological agents show unique ‘fingerprints,’ which could potentially be used for biosensing.”
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According to Fiorenzo Omenetto, the research team likens the concept to “a very peculiar kind of antenna–actually, a lot of small antennas that behave as one. The silk metamaterial composite is sensitive to the dieletric properties of the silk substrate and can monitor the interaction between the silk and the local environment. For example, the metamaterial might signal changes in a bioreactive silk substrate that has been doped with proteins or enzymes.”
The addition of a pure biological substrate such as silk to the gold metamaterial adds immense latitude and opportunity for unforeseen applications, says Professor Richard Averitt, one of Omenettos collaborators from Boston University and an expert on metamaterials.
The resonance response could be used as an implantable electromagnetic signature for contrast agents or bio-tracking applications, says co-author Hu Tao, a former Boston University graduate student who is now a postdoctoral associate in Omenetto’s lab.
To demonstrate the concept, the researchers conducted a series of in vitro experiments that examined the electromagnetic response of the silk metamaterials when implanted under thin slices of muscle tissue. They found that the metamaterials retained their novel resonance properties while implanted. The same process could be readily adapted to fabricate silk metamaterials at other frequencies, according to Tao.
“Our approach offers great promise for applications such as in situ bio-sensing with implanted medical devices and the transmission of medical information from within the human body,” says Omenetto. “Imagine the benefits of monitoring the rate of drug delivery from a drug-eluting cardiac stent, making a perfect absorber that can be implanted to attack diseased tissue by heat, or, someday in the future, wrapping an ‘invisibility cloak’ around an organ to examine the tissue behind it.”
Abstract: Metamaterial Silk Composites at Terahertz Frequencies
Full story: Implantable Silk Metamaterials Could Advance Biomedicine, Biosensing …
Images: Top: Silk-based metamaterial photographed on a background of silk fibers. Side: The tiny, flexible devices can be rolled into capsule-like shapes
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