Textile Encoding Inspired by Langer Lines via Elastically Graded Embroidered Tessellations.

Abstract

Morphological anisotropies and nonlinear mechanical properties shape the kinematic agility of organisms and engineered structures. Tissues, such as skin, act as biological metamaterials whose internal structures, such as packed collagen fibers, produce nonlinear and directional responses. Similarly, hierarchical thread packing governs the mechanical response of textiles. However, the capability of encoding textiles at the fabric level and at a sufficient resolution remains limited. Embroidering triangularly tiled zigzag patterns of inextensible thread on a stretchable fabric is demonstrated to encode distributed, directional stress-strain behavior at subcentimeter resolution, sufficient to mimic complex physiological characteristics such as Langer lines of the skin. The triangular unit cells solved the Königsberg bridge problem of filling a plane with a continuous thread pair. The encoding maps directionality, directional contrast, and magnitude, three parameters that define unit cells' compliance, into hue-saturation-value color space for rapid qualitative design. Cross-talk-free arrays of embroidered restrictors enable scalable augmentation of textile mechanics. The transition threshold from the matrix- to fiber-defined behavior is achieved with 85% fidelity, enabling customizable shape-morphing structures such as restrictor bladder actuators and feet-conforming shoes. Industry-standard machine embroidery scales biomechanics-inspired structures for wearable and environmental robotics and promises future biohybrid technologies.