Research pair theorize metamaterials that exhibit negative compressibility transitions

May 23, 2012 by Bob Yirka report
Negative compressibility contrasted with other effects. Image (c) Nature Materials (2012) doi:10.1038/nmat3331

(Phys.org) -- In the real world of so called “normal” materials, people expect certain things to occur as a result of certain actions. Covering an object with a cloak for example, should hide the object, but the cloak should still be visible (or vice-versa), or if you push or sit on a couch cushion, it should contract. Lately though, new science has been changing our perception of how materials should behave. For example, recent research into metamaterials; materials that aren’t normally found in nature, has been turning some of what we see as normal, on its head. The development of cloaking devices that hide objects and are themselves invisible, is one example.

Now, two researchers Zachary Nicolaou and Adilson Motter, from Northwestern University have proposed another material that doesn’t behave the way we’ve come to expect. They are proposing a metamaterial that reacts contrary to the expected norm, to pressure. When pushed on, it expands, when pulled, it contracts. The two have written a paper describing how such a matermaterial could be made and have had it published in the journal Nature Materials.

While such a material might seem contrary to the laws of nature, the two explain how a metamaterial could be made that actually exploits such laws, rather than changes them. They suggest that if a material were constructed out of a row of four, as yet undetermined elements, where each was made of groups of molecules that are attracted to one another, then, if a force was applied to the inner particles that would be weak enough such that pulling on the metamaterial would cause those bonds to break, then the outer particles would become more strongly attracted to one another, causing compression. If on the other hand the material is squeezed, the inner particles would be brought closer together strengthening those bonds, causing the material to expand.

The two have not yet made an actual metamaterial that exhibits such behavior, but it’s not difficult to see how it could be put to practical use if real ones are constructed; in fact, it’s not a far cry from the properties of the shield Captain America uses to ward off violent attacks. Military vehicles with such a material could expand out when driving over an IED, for example, preventing injury to occupants or car cushions could be fashioned creating perhaps, the smoothest ride ever.

Explore further: New research predicts when, how materials will act

More information: Mechanical metamaterials with negative compressibility transitions, Nature Materials (2012) doi:10.1038/nmat3331

Abstract
When tensioned, ordinary materials expand along the direction of the applied force. Here, we explore network concepts to design metamaterials exhibiting negative compressibility transitions, during which a material undergoes contraction when tensioned (or expansion when pressured). Continuous contraction of a material in the same direction of an applied tension, and in response to this tension, is inherently unstable. The conceptually similar effect we demonstrate can be achieved, however, through destabilizations of (meta)stable equilibria of the constituents. These destabilizations give rise to a stress-induced solid–solid phase transition associated with a twisted hysteresis curve for the stress–strain relationship. The strain-driven counterpart of negative compressibility transitions is a force amplification phenomenon, where an increase in deformation induces a discontinuous increase in response force. We suggest that the proposed materials could be useful for the design of actuators, force amplifiers, micromechanical controls, and protective devices.

Press release

Related Stories

Researchers create “antimagnet” cloaking device

Aug 05, 2011

In what seems like one new cloaking device being discovered after another, researchers in Spain have modeled a device that they say can prevent magnetism from leaking out of a containment container and also prevent it from ...

Scientists create first free-standing 3-D cloak

Jan 26, 2012

Researchers in the US have, for the first time, cloaked a three-dimensional object standing in free space, bringing the much-talked-about invisibility cloak one step closer to reality.

Recommended for you

New filter could advance terahertz data transmission

Feb 27, 2015

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

Feb 27, 2015

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

Precision gas sensor could fit on a chip

Feb 27, 2015

Using their expertise in silicon optics, Cornell engineers have miniaturized a light source in the elusive mid-infrared (mid-IR) spectrum, effectively squeezing the capabilities of a large, tabletop laser onto a 1-millimeter ...

A new X-ray microscope for nanoscale imaging

Feb 27, 2015

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

New research signals big future for quantum radar

Feb 26, 2015

A prototype quantum radar that has the potential to detect objects which are invisible to conventional systems has been developed by an international research team led by a quantum information scientist at the University ...

User comments : 0

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.