A good sweater is like a cozy hug made of yarn. You can thank friction.
New research reveals how knitted fabrics are made. Can take various shapes It can be shaped to fit the contours of your head or body. This effect is the result of friction between adjacent fiber loops that make up the knitted fabric, physicist Jérôme Crassous and colleagues reported on December 13. actual review letter.
When knit fabric stretches and unravels, it bounces back. You can imagine the fabric always returning to the size and shape it had before, similar to an elastic band. But “there is no unique shape,” says Crassous of the University of Rennes in France. “there [are] “A variety of shapes are possible.” This form is called a “metastable state.”
In a series of experiments, researchers stretched square knit fabric made from a basic stitch known as stockinette onto a rectangular frame. They then solved the force and measured the ratio of the length and width of the specimen. The rate varies depending on which direction the fabric is stretched, indicating that the fabric can adopt a variety of metastable states.
The same effect was seen in computer simulations of simplified fiber loops. And when scientists reduced or removed friction from their simulations, many of the metastable states disappeared. Without friction, the fabric will always return to the same shape.
This phenomenon helps explain the “blocking” process that knitters often go through after knitting a garment: wetting the fabric, shaping it, and then laying it out to dry. This process ensures that the fabric is set in the correct configuration to keep your body warm.
