Author: Belinda Ongaro
Institution: University of Alberta
The 21st century has witnessed successful light, sound, and heat cloaking. Now the Karlsruhe Institute of Technology (KIT) has accomplished a similarly unbelievable feat – unfeelability cloaking, or hiding a small object from physical detection with an elastic device.
Despite being small in scale - a mere two millimeters cubed in volume- KIT’s contraption is far from simplistic. The cloaking device consists of a hollow core encased by 3-Dimensional polymer Pentamode metamaterial microstructures fabricated by dip-in direct laser writing optical lithography. For readers unfamiliar with metamaterials and optical lithography, please refer to the appendix below.
The researchers involved in the KIT study built the polymer structure around an object contained in the hollow cavity of a half-cylinder rigid core shell. The precisely arranged cone-shaped microstructures serve to counteract forces exerted on the elasto-mechanical cloak, rendering the underlying object undetectable.
“It is like in Hans-Christian Andersen’s fairy tale about the princess and the pea,” KIT Applied Physicist Tiemo Bückmann explained. “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 cited the precision of the components and the miniscule size of the arrangement as some of the KIT team’s major obstacles. Despite these hurdles, KIT researchers succeeded in disenabling an object from being felt by hands and measurement instruments to an impressive extent, which they quantitatively confirmed using video analysis and autocorrelation software.
Believe it or not, the remarkable properties of this cloaking material have real-world applications beyond the fantastical scope of fairy tales or Harry Potter and Star Trek. Some prospective everyday examples include camping mattresses that are thin and light for easy packing and carpets designed to hide cables and pipelines below. The study is, however, still in its early phases—sleepless princesses will have to endure for now because there is no distinct end-goal in sight.
Metamaterials – artificial materials designed to have mechanical properties not found in nature. Interestingly, these properties are determined by structure, not composition.
Pentamode metamaterials – sometimes called metafluids, these 3D artificial structures behave in a fluid-like manner, but exist as a solid. Their bulk is considered “finite” due to their resistance to compression, however they deform easily. These materials were not successfully fabricated until 2012, although G.W. Milton theorized them in 1995.
Laser writing optical lithography – a method for engraving a desired geometric pattern into the metamaterial. In this case, the microstructures resemble needle shaped cones whose tips meet; a structure that functions to redirect the force applied by fingers and instruments. Dip-in direct is a specific technique that eliminates the issue of height restriction in this process.