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from the Cogswell's-Cosmic-Cogs-vs-Spacely's-Space-Sprockets? dept.
A specifically designed collection of gears is soft on one end and rigid on the other. These robust properties hold even in the event of manufacturing imperfections. This emerging research may lead to new ways of designing geared devices like satellite trackers or watches, and the study has been reported in Physical Review X.
Imagine two connected gear wheels. Turning one clockwise causes the other to turn counterclockwise. Connecting a third gear to both causes the system to get stuck. Leiden physicists Anne Meeussen and Jayson Paulose now have developed a complex assembly of gears that sticks in one place, but which operates in another. Considered as a new metamaterial, it is rigid on one end and soft on the other.
In the video below, this remarkable mechanism seems like magic, but the researchers mathematically devised it. 'The beauty of this principle is that it's a robust system,' says group leader Prof. Vincenzo Vitelli. 'We can decide which parts are soft or rigid, and the mechanism keeps working even if the gears are imperfect. This property is often called topological robustness.'
The video referenced in the story is available on YouTube.
(Score: 4, Insightful) by mhajicek on Wednesday November 23 2016, @10:07PM
So if I build a pattern of levers and gears out of erector set it's now called a metamaterial? People have been doing this for thousands of years.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 0) by Anonymous Coward on Thursday November 24 2016, @12:04AM
Yes, but you also have make the erector set pieces with a 3D printer first.
(Score: 0) by Anonymous Coward on Thursday November 24 2016, @05:31AM
yes, that's what it's called.
the building blocks for most materials are atoms and/or molecules.
when you use building blocks that are themselves chunks of some material, and the end result has macroscopic properties that are fundamentally different from those of the building blocks, you call it a "meta-material".
do you have any more questions?
(Score: 2) by mhajicek on Thursday November 24 2016, @07:04AM
It just seems like an awful fancy name for basic mechanical engineering. Every machine is made of parts and has properties other than the raw materials it's made from.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 0) by Anonymous Coward on Thursday November 24 2016, @07:39AM
for a metamaterial you can write down a macroscopic description, that will work for all chunks of the metamaterial above a certain size.
for instance: a piece of wood has certain elasticity properties; a chunk of metamaterial also has elasticity properties (they are different from those of the piece of wood, but they are relevant in the same equations).
with regular clockworks, the purpose is not to obtain a "material" that has unusual material properties, but rather to construct an analogue computer for some particular differential equations (i.e. construct a physical realization of a dynamical system that follows given equations).
(Score: 2) by mhajicek on Thursday November 24 2016, @09:03AM
Yeah, I get it, but it still seems like a lot of hype for what it is, especially in this case. So many run-of-the-mill things would classify as metamaterials, including wood.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by HiThere on Thursday November 24 2016, @06:50PM
Wood isn't a metamaterial, it's a class of metamaterials. Balsa isn't the same as oak, e.g. And, as with many metamaterials, the grain is important.
You could reasonably consider metameterial to be a generalization of both wood and alloy. If you were doing a class diagram, it would be an ancestor class inserted above both. It's a fancy term because the concept is still fairly new, and there hasn't been time to wear the term down to something more prosaic. If it starts being used enough Zipf's law will ensure that it wears down to something like "metam", but that will require lots of common usage...or a cult among teen-agers.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by mhajicek on Friday November 25 2016, @04:51AM
Now you're getting really pedantic. I said "wood" as referring to any specific piece of wood for simplification purposes. If you're going to be that technical, every sample of wood on the planet is different, as is every sample of steel since the patterns of carbides are different. This would mean that even specifying the exact alloy, heat treat, and manufacturing process would not define a material. There comes a point where generalization is useful.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by HiThere on Friday November 25 2016, @07:00PM
You're starting to get the idea here. Metamaterials typically (possibly not in this case) specify the position of atoms within molecules, and molecules within a larger framework. Trees to this naturally, though not to our specs. But thinks like diamond memory materials depend on the exact placement of nitrogen molecules within the carbon crystal.
OTOH, the same term is also used for positioning pillars to refract waves. If you do it in a harbor, it does the same thing on a larger scale, but if you want to work with light waves you need to be a lot finer in your positioning. And you need to worry about the refractive index of the medium the pillars are embedded in. Etc. That's a static metamaterial. This is about things that move and thus is a new kind of metamaterial, but it is a legitimate use of the term.
A piece of wood is a legitimate metamaterial, if considered in a particular case, but it generally isn't specified carefully enough for that to really be considered a valid use of the term. A doped transistor would be another example of a valid use of the term, but again it's an edge case because it isn't specified at quite the correct level. In a way the term would be better applied to a series of pillars positioned in a harbor to diffract the incoming waves.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.