'Auxetics' are
materials that become thicker perpendicularly to the applied force when stretched. They have a negative
Poisson's ratio, that is, they get thicker and not thinner when stretched. Materials of this sort are expected to have interesting mechanical
properties such as high
energy absorption and
fracture resistance which may be useful in applications such as packing material, knee and elbow pads, robust shock absorbing material, and sponge mops.

Auxetic hexagon
The term auxetic is derived from the
Greek word αυξητικός (auxetikos) which means, ''that which tends to increase'' and has its root in the word αύξησις (auxesis), meaning ''increase'' . Auxetic materials can be single
molecules, or a particular structure of macroscopic matter.
Auxetic materials are quite new. The earliest published example was in ''Science'' in
1987, "Foam structures with a negative Poisson's ratio" by R.S. Lakes of
University of Iowa. The use of the word Auxetic to refer to this property was probably begun in 1991.
External links
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Auxetic Materials - Applications
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Auxetic
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Materials with negative Poisson's ratio
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Auxetic Materials - What are they?
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UK Auxetic Materials network
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Movie of Auxetic Materials(.mov format)