Polymer‐Modulated Evaporation Flow Enables Scalable Self‐Assembly of Highly Aligned Nanowires

Abstract Highly aligned nanowire networks are essential for enabling anisotropic optical, electrical, and sensing functionalities in next‐generation devices. However, achieving such alignment typically requires complex fabrication methods or high‐energy processing. Here, a simple and scalable self‐assembly strategy that uses a polymer additive to modulate fluid flows during solvent evaporation is presented. The addition of carboxymethylcellulose sodium (CMC‐Na) reshapes the evaporation‐driven flow field and generates a compressional flow region near the drying edge. Within this region, rotation‐inducing velocity gradients progressively align silver nanowires (AgNWs) into highly ordered arrays. This unique mechanism yields uniform AgNW coatings with a high degree of nanowire alignment and tunable areal density across centimeter‐scale areas. The resulting films exhibit strong broadband anisotropy, including polarization‐dependent transmission in both visible and terahertz (THz) regimes and angle‐dependent electrical conductivity. The approach also integrates naturally with dip‐coating–based shear alignment, enabling programmable control over alignment direction and spatial patterning. This work establishes a robust, polymer‐enabled mechanism for bottom‐up nanowire alignment and offers a passive, energy‐efficient route for fabricating anisotropic nanostructured coatings.