Despite the material selection limitations faced by biological systems, many natural composites achieve superior toughness and strength to weight ratios through the precise ordering of their microscopic building blocks. Structural bio-composites such as bone, nacre, and stomatopod shells exhibit mechanical properties far exceeding that of their individual elements due to their hierarchical reinforcement. Understanding the strengthening mechanisms of various structural bio-composites can lead to implementing these designs in high performance man-made composite materials. However, there is currently a gap between understanding these structures and being able to successfully assemble them. This research covers a new approach for obtaining polymer-based composites exhibiting bio-inspired, deliberate orientation of reinforcing particles using additive manufacturing.
In this work, we discuss a method of printing discontinuous fiber composites with control over the reinforcing architecture. Super-paramagnetic iron oxide nanoparticles are used to coat less than 5% of the surface of each filler element, which include biocompatible calcium phosphate particles. The labeled fibers can then be manipulated using low magnetic fields (<100 Gauss) during the printing process to create composites with tunable, hierarchical reinforcement. These heterogeneous structures have tunable mechanical properties such as tailored stiffness, hardness, toughness and crack propagation. The capability of creating materials with deterministic material properties lends itself to biological applications including the fabrication of load-bearing biomedical materials and devices. For example, we offer a path forward on using 3D Magnetic printing to produce reinforced and customized bone grafts and orthotics.