Materials Requirements in Fused Filament Fabrication: A Framework for the Design of Next-Generation 3D Printable Thermoplastics and Composites

Fused filament fabrication (FFF), also known as fused deposition modeling, is the leading technology for polymer-based additive manufacturing. The simplicity, along with the cleanness, the affordability, and the multi-material capability, are some of the main advantages that have prompted this success. Nonetheless, the uptake of FFF in industry is hampered by the limited functionality of commercial filaments, that are often based on plain thermoplastics. The future growth of FFF into new markets needs a significant improvement of available materials. However, materials requirements in FFF are complicated and often mutually conflicting. Whereas heuristic approaches to materials design imply significant costs in terms of time, energy, and materials, a critical survey of the main requirements that a new material should fulfill in order to be printable and suitable for commercial adoption is still missing. In order to bridge this gap, the present paper analyzes the workflow from filament production to end-of-life disposal of printed objects, and, for each step, brings to light the governing materials properties. Wherever possible, practical guidelines are given on acceptable values. Existing lacks of knowledge are identified to direct future studies. The ultimate goal is to provide a road map to making materials development in FFF more efficient

Peptide-directed crystal growth modification in the formation of ZnO

Biomolecule-mediated synthesis is fascinating in terms of the level of control and the intricate hierarchical structures of the materials that can be produced. In this study we compare the behavior of a phage display identified peptide, EAHVMHKVAPRP (EM-12) with that of a mutant peptide EAHVCHKVAPRP (EC-12), having additional complexation capability, on the formation of ZnO from solution. The synthesis conditions (Zn(CH3COO)2–NH3 hydrothermal method at 50 °C) were chosen to generate rod-shaped ZnO via layered basic zinc salts (LBZs) as intermediates. Both peptides affected the crystal formation process by moderating the amount of Zn2+ ions in solution (EC12 having a greater effect than EM12) but only EC12 was shown to interact with the solid phase(s) formed during the reaction. Depending on the peptide concentration used, EM-12 was shown to delay and/or suppress ZnO formation. In contrast, additions of EC-12, although leading to the retention of higher levels of Zn2+ ions in solution did not similarly delay the transformation of the intermediate phases to ZnO but were found to dramatically modify the morphology of ZnO crystallites with mushroom shaped crystals being formed. From the results of detailed materials characterization and changes in the morphology observed, the interactions between the peptide(s) and solution and solid state species present during the process of ZnO crystal formation in the presence of EM-12 and EC-12 are proposed