Langmuir Monolayer Fiber Drawing of Aligned Copper Nanowires

Abstract

One-dimensional (1D) nanomaterials are valued for their anisotropic morphology, but they have tendencies to aggregate uncontrollably due to intermolecular interactions and entanglement. We developed a method that can align and bundle 1D nanomaterials into yarn-like microfibers with copper nanowires (CuNWs) as an example of applicable 1D nanomaterials. The method begins by spreading CuNWs into a Langmuir monolayer. The CuNWs form a cohesive, entangled network over the subphase surface, so the CuNWs can be drawn up from one point to collapse the Langmuir monolayer into a microfiber. The drawing motion aligns the CuNWs by pulling them against the subphase’s surface tension. During drawing, residual solvent in the microfiber evaporates to compress CuNWs and facilitate conformal contacts. The assembled microfibers are held together by van der Waals interactions and entanglement between misaligned components. The CuNW microfibers have a Herman’s orientation factor of 0.84, representing significant alignment. These microfibers are cohesive enough to be manipulated into knots and twists. The CuNW microfibers were also examined for their stress–strain properties and electronic conductivity. The discovered technique does not rely on designed surface properties, so 1D nanomaterials with sufficient aspect ratios have a chance to be aligned using this method, including silver nanowires, polystyrene fibers, zinc oxide nanorods, and mixtures of 1D nanomaterials. From its flexible processability, we believe the discovered technique would complement various modifications, such as surface modifications or application-specific chemical compositions.