Physicists are decoding math-y secrets of knitting to make bespoke materials

Enlarge / Introducing topological defects into knitted patterns can shape the (a) out-of-plane elasticity of a stuffed rabbit (left), and (b) the in-plane deformations of knitted textiles (right). (credit: Elisabetta Matsumoto)
Knitted fabrics like a scarf or socks are highly elastic, capable of stretching as much as twice their length, but individual strands of yarn hardly stretch at all. It's the way those strands form an interlocking network of stitches that give knitted fabrics their stretchiness. Physicists are trying to unlock the knitting 'code'—the underlying mathematical rules that govern how different stitch combinations give rise to different properties like stretchiness—in hopes of creating new 'tunable' materials whose properties can be tailored for specific purposes.
'Knitting is this incredibly complex way of converting one-dimensional yarn into complex fabric,' said Elisabetta Matsumoto, a physicist at the Georgia Institute of Technology. 'So basically this is a type of coding.' Figuring out how different stitch types determine shape and mechanical strength could help create designer materials for future technologies—everything from better materials for the aerospace industry to stretchable materials to replace torn ligaments. The models her team is developing may also be useful in improving the realistic animation of clothing and hair in video game graphics. Matsumoto described her research during the American Physical Society's 2019 March meeting taking place this week in Boston.
Knitted fabrics can technically be considered a type of metamaterial (engineered materials that get their properties not from the base materials but from their designed structures), according to Matsumoto, who points to the medieval embroidery technique known as 'smocking' as an early example. From a physics standpoint, smocking uses knots to essentially convert local bending energy into bulk stretching energy.
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