Shear Alignment Polymer Extrusion 3D Printing of High-Loading Nanocomposites With Long-Range Ordered Nanostructures.

Additive manufacturing has long struggled to bridge nanoscale functionalities with complex macroscale geometries, particularly for nanocomposites with high nanofiller loadings and ordered structures. Herein, we report shear alignment polymer extrusion (SHAPE) three-dimensional (3D) printing, a strategy that uses high shear forces to align highly loaded nanomaterials (e.g., boron nitride (BN) nanosheets and carbon nanotubes) along defined directions in polymer matrices, enabling the scalable fabrication of macroscopic nanocomposites with complex 3D architectures. A key advancement is the development of high-loading filaments (e.g., 55 wt% BN in polylactic acid) and a high-shear extrusion system, overcoming the traditional challenges of poor processability and structural integrity in high-filler composites. Post-sintering yields pure nanomaterial architectures that fully replicate the 3D printed geometry with zero volume shrinkage and exceptional thermomechanical stability-withstanding temperatures above the polymer melting and decomposition without structural failure. These materials exhibit tailored functionalities: vertically aligned BN composites show enhanced thermal conductivity (1.07 W/m/K); horizontally aligned BN structures offer efficient thermal insulation (0.071 W/m/K); and BN membranes display robust mechanical performance (a compressive strength of 3.4 MPa). Generalizable to diverse nanomaterials (0D to 2D), SHAPE opens new avenues for cross-scale design in thermal management, energy storage, and advanced structural materials.