Mechanical metamaterial

Up: Metamaterials

Mechanical metamaterials are materials that emulate mechanical properties through structuring at smaller size-scales.
This is relative. Mechanical metamaterials can have their base structures at all scales.
E.g. Cainmaille is crude, textiles are fine. For base structures at the nanoscale see: Gemstone based metamaterial

Reversible assembly is highly desirable.
See: Digital control over matter

Clear delineation to optical metamaterials

The term "Metamaterial" without prefix is often used to refer to optical metamaterials. This may be because:

• Many existing mechanical metamaterials already have a name and are not consciously recognized as such (see below)
• More advanced mechanical metamaterials are maybe experimentally less accessible than optical metamaterials (questionable ...)

Examples for (mechanical) metamaterials: past, present, future

Metamaterial out of the past: chain maille Base-material: metals Structure-size: clearly visible

Metamaterial of today: textiles Base-material: plastics Structure-size: microscopic

Metamaterial of the future: "gem-gum" Base-material: gemstones Structure-size: a few atoms

Today

Known and existing cases of (passive) mechanical metamaterials are:

• Chainmaille
• Textiles
• many natural materials produced by living organisms (bones with structured voids, naca with layered protein and minerals, ...)
• .. there may be a few more that constitute whole different classes ??

Future

Future mechanical metamaterials based on gemstone like compounds
(in particular based on base materials with high potential)

• gemstone based metamaterials

Many unusual properties are (will be) possible.
For more examples see: Metamaterial#Examples

Some few more concrete examples

• (Passive) auxetic metamaterials: Metamaterials which use their non actuated internal structure to create a negative Poisson ratio.
  That is they expand transversally (sidewards) when stretched longitudinally (lengthwise) and they contract transversally when compressed longitudinally.
• Metamaterials with (clearly independent) internal degrees of freedom deliberately left under-constrained.
  If the small structural pieces are sheet shaped and the hinges allow compression to complete collapse without destruction one ends up with origami like structures.
  Note that metamaterials are by far not limited to origami structures.
  Such structures can be made active structures by adding actuators independently acting on the separate degrees of freedom.
• Metamaterials using internal flexing or hinging to act as complex mechanisms / machines.
  Giving up on long range periodicity (translation symmetry) symmetry blurs the line to (nano)machinery and (nano)mechanical computation.
  What makes a metamaterial is the presence of at least a little bit of repetition.

Non-mechanical metamaterials

The complement to mechanical metamaterials are the non-mechanical metamaterials. These include:

• Electromagnetic metamaterial with the subclasses of Optical metamaterials and crude Radio frequency metamaterials
• Thermal metamaterial
• Electrical metamaterials
• ... many more other types of metamaterials

Related

• Digital control over matter
• Emulated elasticity
• Metamaterial
• Gemstone based metamaterial
• Topological mechanical metamaterial
• Going off-topic: Tensegrity

External links

• Auxetics – one peculiar example of an nigh infinite amount of possibilities