All-Organic Electroactive Shape-Changing Knitted Textiles Using Thermoprogrammed Shape-Memory Fibers Spun by 3D Printing

Abstract

Here, we present knittable shape-memory polymeric fibers extruded using a 3D-printer nozzle-based melt-spinning method for high throughput of composition and condition testing. These structures are used as the basis for electroactive shape-changing knitted textiles combining several types of fibers, including organic fibrous heaters. These structures represent a different approach to "on-demand"shape-memory fibers and can be incorporated into a variety of textile architectures, including inlaid knitting, diagonal interlacements, and a knit/purl design for an anisotropic knitted texture. The influence of manufacturing process parameters (e.g., drawing ratio during melt-spinning) on physical properties of the shape-memory fibers was measured using X-ray diffraction, thermomechanical cycling, scanning electron microscopy, and mechanical testing. The degree of crystallinity increased from 19.4 to 22.4% with the increased drawing ratio, with a maximum strain % of 450 and the fibers being able to lift 457 times their own weight. Further, we present a scalable strategy for bicomponent filament production, in which two distinct polymers are melt-spun in a side-by-side configuration and when actuated showed a coiled structure with different mechanical and thermal behavior than pure SMP fibers. The knitted textiles, obtained with a computer-controlled knitting machine able to produce 3D knitted structures, are deformed from two-dimensional planar structures to three-dimensional conformations by applying a voltage to the organic fibrous heaters. The deformed structure can be fixed by removing the applied voltage and can be returned to a planar configuration by heating and applying an uniaxial stress. Therefore, a hierarchical approach for fully textile-based, bendable, knittable, and electroactive soft actuators is presented. The results presented here demonstrate lab-scale production and high-throughput screening of advanced fibers with tunable properties.