What does auxetic mean?
Auxetic describes an unusual class of materials and structures that grow wider, rather than narrower, when they are stretched — the opposite of how ordinary elastic substances like rubber behave. This counterintuitive property arises from their internal geometry: repeating patterns such as rotating squares or re-entrant honeycombs unfold and open up under tension, giving the material what engineers call a negative Poisson's ratio. The term also functions as a noun, referring to any material with this behaviour, with 'auxetics' denoting the field of study. Because stretching makes them thicker, auxetic materials resist tearing, absorb energy well, and can tighten around curved shapes, making them valuable in stents, protective armour, sports footwear, and smart textiles. Though firmly rooted in laboratory research since the late twentieth century, the word has entered mainstream science writing as applications move toward commercial products, making it a useful term for describing one of modern engineering's most striking design principles.
(Of a material or structure) having a negative Poisson's ratio, so that it expands laterally when stretched rather than becoming thinner.
"Auxetic foams were tested for impact protection because they densify at the point of contact."
Most common usage; found almost exclusively in technical and scientific writing.
A material or structure that exhibits auxetic behaviour.
"The researchers compared several auxetics to find the best candidate for the implant."
Frequently used in the plural or collective form 'auxetics' to denote the class of such materials.
Used either as the ordinary plural of the noun ('several auxetics') or as a mass noun naming the field of study ('the study of auxetics').
"Recent advances in additive manufacturing have accelerated interest in auxetics."
Pull on an auxetic fabric and it gets fatter instead of skinnier — the exact opposite of a rubber band.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of auxetic
Auxetic derives from the Greek verb auxein, meaning 'to increase' or 'to grow', via the noun auxēsis, 'growth'. It entered scientific English in the twentieth century, first appearing in biological contexts before being adopted in the 1980s by materials scientists to describe structures with negative Poisson's ratios. It shares this Greek root with auxin, the plant-growth hormone, and more distantly connects to Latin-derived words of similar meaning such as augment and author.
Related word forms
How auxetic is actually used
A specialist term used chiefly in materials science, engineering, and design literature. As a noun it is usually treated as countable ('an auxetic') or collective ('auxetics'), and the adjective is sometimes written capitalized in early literature. It carries no informal register; outside its technical context it may need brief explanation.
Easily confused with auxetic
An auxin is a plant hormone that regulates growth, whereas auxetic describes a material that expands sideways when stretched; both derive from Greek roots for growth but belong to entirely different fields.
Aesthetic concerns beauty and artistic taste, while auxetic is a technical term in materials science about how a structure deforms under tension.