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DateDate: 14-12-2018, 05:58

Modern metamaterials are very much like technologies known to us from science fiction. Due to the unique properties of such materials, you can create incredible things, invisibility cloaks that hide objects in different wavelengths of the electromagnetic spectrum, and in practice such technologies are already used in mobile phone antennas, for example. Note that all the metamaterials, which we have repeatedly told on the pages of our site, have a set of albeit unique, but fixed properties, which significantly limits their scope. But not so long ago, researchers from Lawrence Livermore National Laboratory (awrence Livermore National Laboratory, LLNL) and the University of California at San Diego developed a new class of metamaterials — mechanical metamaterials that can become rigid or flexible in response to an external magnetic field, writes dailytechinfo .org.
To create a new wonder-metamaterial, researchers used the so-called 4D printing technology. The name of this technology is derived from the fact that objects made using three-dimensional printing can change their shape over time, which acts as a fourth dimension. As a rule, changes in the shape of an object occur under the influence of some external factor — high temperature, hydration, or a magnetic or electric field.
The basis of the new technology is materials capable of reacting to external fields (FRMM, field-responsive metamaterial). However, unlike materials used in other 4D printing technologies, FRMM materials do not change their shape, the changes affect some of their physical properties, hardness, in this case. Creating FRMM materials turned out to be quite simple: instead of the monolithic structure of the printed object, a tubular hollow structure is formed. And at the next stage, these cavities are filled with a special magnetic fluid.
Magnetic fluid consists of tiny particles of magnetic material, uniformly mixed in the volume of a non-magnetic solvent. When such a liquid comes under the influence of an external magnetic field, the particles in its volume are ordered, aligning along the magnetic field lines, and the material becomes almost a solid monolith. In the absence of a magnetic field, the magnetic fluid behaves like a normal viscous fluid, able to flow freely in any direction.
"A careful calculation of the elements of the metamaterial tubular structure and the composition of the magnetic fluid allowed us to obtain a 318 percent increase in the hardness of the material under the influence of a magnetic field," the researchers write, "At the same time, the transformation of material properties occurs in less than a second of time."
Researchers predict that a new type of FRMM material can be used to make moving elements of “soft” robots, elements of “smart” wearable electronic devices, and in many other applications. However, before the practical use of FRMM materials becomes economically viable, scientists will need to develop new production technologies that allow production of such materials in industrial quantities and at low cost.