Researchers Knit Fabrics That Snap Between Shapes, Become Switches

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have engineered machine-knitted fabrics that exhibit multistability, meaning they can snap between several distinct, stable three-dimensional shapes. This development opens doors for creating programmable and shape-shifting textiles.

The team utilized weft knitting, a process common in the garment industry, combined with highly elastic yarns and a technique called plating. Plating exposes different yarns on each side of the fabric, allowing for the creation of dense, thick textiles that naturally curl into specific shapes. This curling behavior is similar to how a cut T-shirt might curl up at the edges, but is precisely controlled by yarn selection and machine parameters to achieve a "snappy" quality.

To demonstrate the practical applications of these multistable knits, the researchers integrated fine conductive yarns. These additions transformed the fabrics into soft, stretchable electric switches that change their electrical state as the textile snaps between its configurations. Examples include a knitted shell that functions as an on/off switch for an LED, and a wearable textile sensor designed to count steps when worn on the knee or elbow by registering the snapping motion.

The knitting machines used are comparable to those in industrial garment factories, suggesting that the technology has significant potential for rapid scalability. The research bridges textiles with the field of nonlinear mechanical metamaterials, where structures are designed to exhibit specific mechanical responses like buckling and snapping. The team envisions future textiles that can unobtrusively monitor movement, provide haptic feedback, or even change shape on demand.