Now, invisibility cloak that blocks touch!

Scientists have developed a new type of invisibility cloak that prevents an object from being touched.
The invisibility cloak may one day lead to very thin mattresses or carpets hiding cables and pipelines below, researchers said.
In the past years, various invisibility cloaks have been developed. Optical invisibility cloaks, for instance, make objects appear invisible, while others appear to let heat or sound pass uninfluenced.
Scientists from Karlsruhe Institute of Technology (KIT) in Germany have developed a mechanical invisibility cloak that prevents an object from being touched.
The invisibility cloak is based on a so-called metamaterial that consists of a polymer. Its major properties are determined by the special structure.

"We build the structure around the object to be hidden. In this structure, strength depends on the location in a defined way," said Tiemo Buckmann, the first author of the study.

"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," Buckmann said.
The metamaterial is a crystalline material structured with sub-micrometer accuracy. It consists of needle-shaped cones, whose tips meet.
The size of the contact points is calculated precisely to reach the mechanical properties desired. In this way, a structure results, through which a finger or a measurement instrument cannot feel its way, researchers said.

In the invisibility cloak, a hard cylinder is inserted into the bottom layer. Any objects to be hidden can be put into its cavity.
If a light foam or many layers of cotton would be placed above the hard cylinder, the cylinder would be more difficult to touch, but could still be felt as a form.
The metamaterial structure directs the forces of the touching finger such that the cylinder is hidden completely.
"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," Buckmann said.

The study was published in the journal Nature Communications.