Long Liquid Crystal Elastomer Fibers with Large Reversible Actuation Strains for Smart Textiles and Artificial Muscles

TLDR

The study develops a direct‑ink‑write printing method to fabricate long, soft, reversibly actuatable liquid crystal elastomer fibers for use in smart textiles, soft robotics, and biomedical devices. The fibers are produced by extruding a nanoclay‑laden LCE ink onto a rotating mandrel, followed by thermal curing, mechanical stretching, and photocuring to align liquid crystal chains. Optimized fibers reach 1.5 m length, 2 MPa modulus, 51 % reversible strain, over 100 % failure strain, and can be knit, sewn, woven into smart textiles or used to emulate bicep muscles.

Abstract

A method for fabricating long, soft, and reversibly actuatable liquid crystal elastomer (LCE) fibers by using direct ink write (DIW) printing was developed. Here, the LCE was produced based on a two-stage thermal-photo curing reaction between a difunctional acrylate monomer and thiol. The LCE ink, mixed with nanoclay to increase the viscosity, was extruded through a nozzle onto a rotating mandrel to obtain a long fiber. After printing, the fiber was first thermally cured on the mandrel, then mechanically stretched, and photocured to achieve liquid crystal chain alignment for stress-free reversible activation. Upon optimizing the ink viscosity and DIW printing parameters, long fibers (up to 1.5 m long from the laboratory) were obtained. The resulting fiber had a modulus of 2 MPa, 51% actuation strain, and a failure strain of well over 100%. The potential of these fibers for applications was demonstrated. The LCE fibers were knit, sewn, and woven to form a variety of smart textiles. The fiber was also used to mimic bicep muscles with both large activation force and activation strain. By incorporating further intelligent characteristics, such as conductivity and biosensing into a single fiber, the LCE fibers could be potentially used for smart clothing, soft robotics, and biomedical devices.