Design and Fabrication of Origami-Inspired Knitted Fabrics for Soft Robotics

TL;DR

This work tackles the problem of achieving programmable foldability in soft robotics while maintaining wearer comfort. It introduces a general method to translate origami crease patterns into knitted designs by programming stitch types and selective heat fusible yarn, enabling stiff panels around compliant creases within a single fabric. Key contributions include (i) a practical origami-to-knit design method, (ii) experimental folding characterization showing improved directionality and reduced undesired bending, and (iii) demonstrations of origami tessellations (Miura-ori, Yoshimura, Kresling) and a wearable knitted Kaleidocycle that can rotate continuously with radius modulation. The approach offers a scalable, comfortable platform for reconfigurable wearables and soft robotics, with potential impact on assistive devices and human–robot interaction systems; mathematically, it leverages folding moment metrics and a directionality ratio $R = M_{forward} / M_{backward}$ to quantify performance improvements, all within a multimaterial knitting framework.

Abstract

Soft robots employing compliant materials and deformable structures offer great potential for wearable devices that are comfortable and safe for human interaction. However, achieving both structural integrity and compliance for comfort remains a significant challenge. In this study, we present a novel fabrication and design method that combines the advantages of origami structures with the material programmability and wearability of knitted fabrics. We introduce a general design method that translates origami patterns into knit designs by programming both stitch and material patterns. The method creates folds in preferred directions while suppressing unintended buckling and bending by selectively incorporating heat fusible yarn to create rigid panels around compliant creases. We experimentally quantify folding moments and show that stitch patterning enhances folding directionality while the heat fusible yarn (1) keeps geometry consistent by reducing edge curl and (2) prevents out-of-plane deformations by stiffening panels. We demonstrate the framework through the successful reproduction of complex origami tessellations, including Miura-ori, Yoshimura, and Kresling patterns, and present a wearable knitted Kaleidocycle robot capable of locomotion. The combination of structural reconfigurability, material programmability, and potential for manufacturing scalability highlights knitted origami as a promising platform for next-generation wearable robotics.

Figures (7)

• Figure 1: Translation of a paper origami pattern into a knitted origami structure. (A) Paper origami preliminary base pattern (left), and translated knit origami pattern (right). In the knit pattern, different colors refer to different stitch types, where the details and the enlarged pattern are provided in Figure \ref{['fig:Fig4']}. (B) Deployed configurations of paper and knitted origami. (C) Collapsed configurations of paper and knitted origami.
• Figure 2: Graphical representation of stitch patterns that create folds (dashed lines) and the resulting folding moments due to asymmetry and local thickness changes created by stitch patterns (arrows). (A) Front view of a horizontal mountain fold. (B) Rear view of a vertical valley fold. (C) Front view of a backward-slant diagonal ($\diagdown$) mountain fold. (D) Rear view of a forward-slant diagonal ($\diagup$) valley fold.
• Figure 3: A schematic of the framework to translate an origami pattern into a knit structure. The process consists of five steps: (1) identify the target origami pattern, (2) measure the dimensions of a single knit stitch, (3) generate a stitch-level grid, (4) apply the prescribed stitch types (e.g., knit, purl, tuck, twist) along the crease lines, and (5) selectively add heat-fusible yarn to program the fold behavior. The details of the pattern in step 5 are shown in Figure \ref{['fig:Fig4']}
• Figure 4: Detailed patterns corresponding to Figure \ref{['fig:Fig1']}(A). Symbols follow the Knitting Font Collection. The colored cells represent distinct stitch types: gray cells correspond to knit stitches with acrylic and heat-fusible yarn. All other colors represent stitches made with acrylic yarn only: white (knit), yellow (purl), blue (tuck), red (left twist), and green (right twist).
• Figure 5: (A) Photograph of the experimental setup. (B) Front and bottom views of sample with a horizontal mountain fold without heat fusible yarn (top) and with heat fusible yarn (bottom). Without heat fusible yarn, the edge of sample curl due to inherent asymmetry of the yarn geometry. (C) Experimental results for the horizontal mountain fold in forward and backward directions, normalized by crease length. The backward results are slightly shifted to avoid overlap with the forward results. The error bars indicate the minimum and maximum of measured values. (Top) Comparison between the jersey fabric and the patterned fabric made of acrylic yarn only. (Bottom) Comparison between the jersey fabric and the patterned fabric with heat fusible yarn.