The Effects of Shear Stress on the Micromechanical Properties of 3D Printable Biopolymer Nanocomposites Using a Custom-Designed Extrusion-Based 3D Printer

Current advancements in 3D printing technology have the potential to facilitate the production of scaffolds and implants for various biomedical applications, including bone repair and regeneration. 3D printed patient-specific bone-inspired nanocomposite grafts might be a viable alternative to current bone repair treatment methods if they provide appropriate anatomic structure, biocompatibility, and adequate mechanical properties. In the current work, a 3D printable nanocomposite biomaterial ink with bone cell biocompatibility (in vitro) is printed while adjusting shear stress during extrusion using a custom-designed 3D printer to investigate the shear stress effect on the mechanical properties of the 3D printed nanocomposite. Tensile test results, as well as polarized light microscopy and differential scanning calorimetry analyses, reveal that increasing the applied shear stress from 3.5 to 14 kPa during extrusion-based 3D printing in a custom-built 3D printer, increased the strength, tensile modulus, and toughness of printed nanocomposite filaments by about three-fold. This improvement is attributed to increased crystallinity in the thermoset biopolymer matrix due to the higher shear stress and the nano-confinement effect. This implies that greater shear during layer-by-layer extrusion-based 3D printing might be employed to create more robust mechanically competent 3D printed nanocomposite bone grafts. Greater shear stress applied during direct ink writing (DIW) of biopolymer-nanohydroxyapatite nanocomposite biomaterial ink using a custom built, mandrel bed 3D printer results in increased degree of crystallinity within the printed material (measured as enthalpy of melting and observed as spherulite formation) leading to greater elastic modulus and tensile strength.image (c) 2024 WILEY-VCH GmbH