Elastic invisibility cloak hides materials from touch sense

June 20, 2014
Mechanical invisibility cloak: Metamaterials protect objects on the lower side from touching. Credit: T Bückmann / KIT

In the past years, invisibility cloaks were developed for various senses. Objects can be hidden from light, heat or sound. However, hiding of an object from being touched still remained to be accomplished. KIT scientists have now succeeded in creating a volume in which an object can be hidden from touching similar to a pea under the mattress of a princess. The results are now presented in the renowned Nature Communications journal.

Magicians and illusionists make things disappear by means of a skilled use of mental delusions and diversionary tactics. KIT researchers, by contrast, use invisibility cloaks based on the laws of physics. In the past years, various physical invisibility cloaks were developed. Optical invisibility cloaks, for instance, make objects appear invisible, while others appear to let heat or sound pass uninfluenced. A completely new type of is the mechanical one developed by KIT scientists. It 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," explains Tiemo Bückmann, KIT, the first author of the article. "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." 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 desired. In this way, a structure results, through which a finger or a measurement instrument cannot feel its way.

Mechanical invisibility cloak: Metamaterials protect objects on the lower side from touching. Credit: T Bückmann / KIT

In the invisibility cloak produced, 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," Bückmann explains.

The material consists of precisely calculated needle-shaped elements, such that strength depends on the location in a defined way. Credit: T Bückmann / KIT

Implementation of such a mechanical invisibility cloak is rather complex. After the definition of the desired mechanical properties, the physical basic equations are inverted mathematically in order to draw conclusions with respect to the structure of the metamaterial. Using this method, materials not encountered in nature can be planned. Examples are solids which are stiff to pressure, but soft to shear. For manufacture from the polymer, the direct laser writing method of the KIT spinoff Nanoscribe is applied. It reaches the required precision over the complete sample length of several millimeters.

The mechanical invisibility cloak represents pure physical fundamental research, but might open up the door to interesting applications in a few years from now, as it allows for producing materials with freely selectable mechanical properties. Examples are very thin, light, and still comfortable camping mattresses or carpets hiding cables and pipelines below.

Explore further: Karlsruhe invisibility cloak: Disappearing visibly

More information: Paper: DOI: 10.1038/ncomms5130

Related Stories

Karlsruhe invisibility cloak: Disappearing visibly

May 18, 2011

"Seeing something invisible with your own eyes is an exciting experience," say Joachim Fischer and Tolga Ergin. For about one year, both physicists and members of the team of Professor Martin Wegener at KIT's Center for Functional ...

New invisibility cloak hides objects from human view

July 27, 2011

For the first time, scientists have devised an invisibility cloak material that hides objects from detection using light that is visible to humans. The new device is a leap forward in cloaking materials, according to a report ...

One size cloaks all

November 21, 2012

A metamaterial invisibility cloak that can adapt to hide different sized objects is demonstrated by in Nature Communications this week. The findings represent a useful advance for more practical applications of metamaterial ...

Researcher construct invisibility cloak for thermal flow

May 8, 2013

By means of special metamaterials, light and sound can be passed around objects. KIT researchers now succeeded in demonstrating that the same materials can also be used to specifically influence the propagation of heat. A ...

Recommended for you

A new form of real gold, almost as light as air

November 25, 2015

Researchers at ETH Zurich have created a new type of foam made of real gold. It is the lightest form ever produced of the precious metal: a thousand times lighter than its conventional form and yet it is nearly impossible ...

New 'self-healing' gel makes electronics more flexible

November 25, 2015

Researchers in the Cockrell School of Engineering at The University of Texas at Austin have developed a first-of-its-kind self-healing gel that repairs and connects electronic circuits, creating opportunities to advance the ...

Getting under the skin of a medieval mystery

November 23, 2015

A simple PVC eraser has helped an international team of scientists led by bioarchaeologists at the University of York to resolve the mystery surrounding the tissue-thin parchment used by medieval scribes to produce the first ...

Atom-sized craters make a catalyst much more active

November 24, 2015

Bombarding and stretching an important industrial catalyst opens up tiny holes on its surface where atoms can attach and react, greatly increasing its activity as a promoter of chemical reactions, according to a study by ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.