A portable invisibility cloak that can make small objects disappear was devised by German scientists ‘without magic spells’ for students.
Researchers from the Karlsruhe Institute of Technology (KIT) in Germany have engineered systems that bend light around an object, shielding it from detection. Although most are very tiny and only work at small wavelength ranges, it can still make objects vanish from sight.
Traditionally, when scientists try to divert light around an object to render it invisible, it can be difficult because they have to compensate for the increased distance the light must now travel.
But the KIT team designed their cloak-scattering material that slows down the effective propagation speed of the light waves through the medium. Then the light can be sped up again to make up for the longer path length around the veiled object.
The object intended to become invisible is placed inside a hollow metal cylinder coated with acrylic paint, which diffusely reflects light. The tube is embedded within a block of silicon-based organic polymer (PDMS) infused with titanium dioxide nanoparticles that make it scatter light.
“Our cloak takes advantage of the much lower effective propagation speed in light-scattering media,” said Robert Schittny, who led the research project. “As we seemingly slow down the light everywhere, speeding it up again in the cloak to make up for the longer path around the core is not a problem.”
If the average time it takes light to travel through the PDMS block is just in the right amount to the average time it takes to travel through the cloak, the core will become invisible.
The scientist hope to take the invisibility cloak into classrooms and use it for demonstrations, as it is in a complete solid-state and can be easily transported. “It is a macroscopic cloak that you can look at with your bare eyes and hold in your hands,” said Schittny.
“With a reasonably strong flashlight in a not-too bright room, it is very easy to demonstrate the cloaking. That means no fancy lab equipment, no microscopes, no post-processing of measurement data. The effect is just there for everyone to see.”
Researchers hope the cloak will be used in classrooms and labs to excite and educate students about physics and engineering systems.