It takes a certain daring to invent a technology that mimics magic a step beyond anything JK Rowling contemplated, but that is what scientists at the Karlsruhe Institute of Technology (KIT), Germany, claim to have done. Where Rowling gave Harry Potter an invisibility cloak that prevented the wearer from being seen, the KIT team claim they can stop if from being felt, or even sensed by a force measuring device.
Technologies that hide objects from one of our senses are referred to as invisibility cloaks, even when the sense is not vision. Examples include not only ways to prevent us seeing things, but also hearing soundwaves bounce off them or detecting their influence on heat.
As impressive as these are, they, like Harry's cloak do not interfere with our sense of touch. We could, if we wanted to hide the nature of an object, shroud it in material so that it could not be directly felt. Nevertheless, anyone touching the packaging would know that something was there.
The KIT team however, have produced a polymer metamaterial that can shield objects placed inside it so that they appear not to be there at all. "We build the structure around the object to be hidden. In this structure, strength depends on the location in a defined way," explains Tiemo Bückmann, the first author of the Nature Communications reporting their success.
"It is like in Hans-Christian Andersen's fairy tale about the princess and the pea. The princess feels the pea in spite of the mattresses. When using our new material, however, one mattress would be sufficient for the princess to sleep well," Bückmann explains.
In order to achieve their goal Bückmann and his colleagues created a crystalline material of long, thin cones whose tips meet. The contact points are adjusted to fool the senses so that it as if the underlying object does not exist at all. It is not just the human body that can be tricked in this way, The paper claims, “The measured and the calculated displacement fields show very good cloaking performance. This means that one can elastically hide objects along these lines.”
T. BÜCKMANN / KIT The metamaterial's strength varies with location so that the presence of the container is disguised.
"The precision of the components combined with the size of the complete arrangement was one of the big obstacles to the development of the mechanical invisibility cloak," Bückmann says. The tiny cloak created in KIT's lab is of no practical value, and the team say they did the work as part of fundamental physics research, rather than with any applications in mind. Nevertheless, they suggest it might one day be possible to make carpets that hide cables run beneath them, or camping mattresses that are both light and thin, but protect the camper against rocky ground or intrusive tree roots.