Power of Fiber Twist

Abstract

Functional polymer fibers show promising mechanical, thermal, and electrical properties, and may find important applications in wearable electronics, cooling, and tough fibers. Here by mimicking the nature, we designed functional fiber materials with periodical geometrical structures, such as twisting, coiling, and buckling. These fiber materials exhibit interesting properties, due to the periodical twisting, coiling, and buckling of the macromolecular chains. (1) We prepared artificial spider silks by using “twisted sheath-core” hydrogel fibers with chemical and physical cross-linking points, whose mechanical strength and toughness are close to those of the natural spider silk. (2) Twist insertion in natural fiber materials e.g. silkworm silk, cotton, bamboo fiber, hair fiber produces moisture driven artificial muscles, which can rotate, contract, and elongate in response to moisture. (3) Inserting twist highly improved the cooling efficiency of elastomer fibers from 32% to 67%, and rigid polymer fibers also show high cooling temperature by twist insertion. (4) We prepared highly elastic conductive fibers by using buckled conductive layer with zero-Poison’s ratio, realizing ultra-stable resistance during large elongation. (5) Based on the above periodical structures, we designed multi-functional materials with hierarchical geometrical structures, realizing strain sensors, artificial muscles, and robotics.