Even at small sizes, the flexibility of the material is likely to confer some big advantages. “You really would like to be able to shape optical metamaterials into cylinders or spherical sections.” This could allow, for example, the creation of curved superlenses that could magnify objects so small that they currently can’t be seen with optical lenses due to diffraction effects. “On rigid substrates, it’s just next to impossible to fabricate that kind of thing,” says Duke University’s Cummer, but with a flexible material, “you could fabricate flat and easily bend it into shape.”
Di Falco believes it should be possible to stack sheets of Metaflex together to create thick layers and blocks of the material, creating the first optical metamaterial with a significant three-dimensional bulk. Such a development would open the door to new properties, including, perhaps, the ability to work with more than a single wavelength at a time. Other researchers have been able to create metamaterials that can be tuned to respond to different single wavelengths after fabrication, but ideally, they’d like a material that can work across a wide band of wavelengths simultaneously. This might be achieved through stacking sheets of MetaFlex, each tuned to a different wavelength.
The researchers’ next step is to create these stacks and study how the properties of Metaflex change when sheets are twisted, stretched, or bent.
Ultimately, Di Falco says, Metaflex could have applications such as manipulating light from an LED built into a contact lens for augmented reality, so that computer-generated images are projected onto the wearer’s retina. And of course, there’s invisibility. “If you have something flexible, you could embed it into a fabric. Then you could think of tuning the properties of each individual layer to change the response of the fabric, giving something similar to camouflage. So, yes—there’s some grounds for [an invisibility cloak]. Not tomorrow. But that’s what I’ll be working on,” says Di Falco.