Fabrication and Characterization of High Aspect Ratio Conducting Polymer Fibers

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Fabrication and Characterization of High Aspect Ratio Conducting Polymer Fibers Miguel A. Saez1, Lauren Montemayor1, Priam V. Pillai1 and Ian W. Hunter1 1

Bio-Instrumetation Lab, Department of Mechanical Engineering, Massachusetts Institute of Technology. 77 Massachusetts Ave, Cambridge MA. ABSTRACT Electroactive conducting polymers are currently studied for use in smart textiles that incorporate sensing, actuation, control, and data transmission. The development of intelligent garments that integrate these various functionalities over wide areas (i.e. the human body) requires the production of long, highly conductive, and mechanically robust fibers. This study focuses on the electrical, mechanical and electrochemical characterization of high aspect ratio polypyrrole fibers produced using a novel, custom-built fiber slicing instrument. In order to ensure high conductivity and mechanical robustness, the fibers are sliced from tetraethylammonium hexafluorophosphate-doped polypyrrole thin films electrodeposited onto a glassy carbon crucible. The computer-controlled, four-axis slicing instrument precisely cuts the film into thin, long fibers by running a sharp blade over the crucible in a continuous helical pattern. This versatile fabrication process has been used to produce free-standing fibers with square cross-sections of 2 μm × 3 μm, 20 μm × 20 μm, and 100 μm × 20 μm with lengths of 15 mm, 460 mm, and 1,200 mm, respectively. An electrochemical dynamic mechanical analyzer built in-house for nano- and microfiber testing was used to perform stress-strain and conductivity measurements in air. The fibers were found to, on average, have an elastic modulus of 1.7 GPa, yield strength of 37 MPa, ultimate tensile strength of 80 MPa, elongation at break of 49%, and an electrical conductivity of 12,700 S/m. SEM micrographs show that the fibers are free of defects and have cleanly cut edges. Preliminary measurements of the fibers’ strain-resistance relationship have resulted in gage factors suitable for strain sensing applications. Initial tests of the actuation performance of fibers in neat 1-butyl-3-methylimidazolium hexaflourophosphate have shown promising results. These monofilament fibers may be spun into yarns or braided into 2- and 3-dimensional structures for use as actuators, sensors, antennae, and electrical interconnects in smart fabrics. INTRODUCTION Flexible microwires fabricated from conducting polymers have a wide range of possible applications including smart textiles, high fidelity neural recording, micro antennas, and flexible polymer-based electronics. Smart textiles that incorporate sensing, information processing and actuation in a flexible platform have garnered increased interest in recent years. Advances in textile nanotechnologies are enabling the integration of these various functionalities into wearable electronic systems while maintaining the look and feel of traditional fabrics [1]. With demand for smart textiles growing in industries ranging from military and security to healthcare an