3D printed volumetric knits

Knitted fabrics are extremely robust under mechanical strain, extreme environments and repeated use. These capabilities are achieved through an hierarchical architecture where fibers are spun to form yarns, yarns loop and interlock to form periodic knit swatches, and these are sown to form fabrics. In this sense, knit fabrics can be interpreted as architected materials. However, their internal microstructure is largely limited by the industrialized manufacturing technology, the tunability of mechanical behavior of knits remain unexplored, and they remain 2D. Here, we demonstrate the use of additive manufacturing to study knits as novel form of architected materials. First, we replicate the form and behavior of traditional knits across different knitting parameters. Second, we explore the couple behavior of a knit under biaxial stretch. We show that its behavior in one direction can be tuned by imposing a pre-stretch in the other. Lastly, exploiting freeform fabrication, we demonstrate a 3D volumetric knitted architected material and explore its triaxial behavior. Showing the scale-invariant nature of such architected material, we utilize two-photon lithography to fabricate the smallest knit.