3D Bioplotter Research Papers

Equiatomic CoCuFeNi high-entropy alloy microlattices are created by 3D-extrusion printing of an ink containing a blend of binary oxides (Co3O4+CuO+Fe2O3+NiO) and graphite (C) powders. After printing, the green parts are subjected to a series of heat treatments under Ar leading to (i) carbon reduction of the oxides to form metallic particles, (ii) interdiffusion of these metallic particles to create an alloy, and (iii) sintering to remove porosity. The phase evolution in individual extruded filaments (similar to struts in the microlattices) is observed by in-situ X-ray diffraction, showing that intermediate suboxide phases (Cu2O, CoO, Fe3O4, CuFeO2, and FeO) form as the…

Three-dimensional (3D)-printed bioactive scaffolds that can be produced rapidly could offer an individualized approach for treating full-thickness skin defects. Decellularized extracellular matrix (dECM) and mesenchymal stem cells have been proven to support wound healing. Adipose tissues obtained by liposuction are rich in adipose-derived dECM (adECM) and adipose-derived stem cells (ADSCs) and thus represent a natural source of bioactive materials for 3D bioprinting. Herein, ADSC-laden 3D-printed bioactive scaffolds consisting of gelatin methacryloyl (GelMA), hyaluronic acid methacryloyl (HAMA), and adECM were fabricated with dual properties of photocrosslinking in vitro and thermosensitive crosslinking in vivo. adECM was prepared by decellularization of human lipoaspirate…

An oxygen-resistant refractory high-entropy alloy is synthesized in microlattice or bulk form by 3D ink-extrusion printing, interdiffusion, and silicide coating. Additive manufacturing of equiatomic HfNbTaTiZr is implemented by extruding inks containing hydride powders, de-binding under H2, and sintering under vacuum. The sequential decomposition of hydride powders (HfH2+NbH+TaH0.5+TiH2+ZrH2) is followed by in situ X-ray diffraction. Upon sintering at 1400 °C for 18 h, a nearly fully densified, equiatomic HfNbTaTiZr alloy is synthesized; on slow cooling, both α-HCP and β-BCC phases are formed, but on quenching, a metastable single β-BCC phase is obtained. Printed and sintered HfNbTaTiZr alloys with ≈1 wt.% O shows excellent mechanical properties…

Ni-Co-Fe-based high-entropy superalloys (HESAs) are fabricated into microlattices via a three-step process: (i) layer-by-layer extrusion of inks containing elemental powders (Ni, Co, Fe, Cr, Ti) and TiAl3 powders; (ii) sintering to densify and homogenize the struts; (iii) aging to achieve a γ/γ’ microstructure. The struts of the microlattices show a nearly pore-free and fully-homogenized microstructure. Increasing the Ti concentration from 4 at% (Al9Co26Cr7Fe16Ni38Ti4) to 9 at% (Al8Co25Cr7Fe15Ni36Ti9) leads to a significant increase in the volume fraction of strengthening γ’ precipitates, from 51 to 78 %. Furthermore, in the Ti-rich composition, the γ’ precipitates exhibit a sharp-edged cubic morphology with larger…

Microlattices with orthogonal 0-90° architecture are 3D-extrusion printed from inks containing a blend of oxide powders (Co3O4, CuO, Fe2O3, and NiO) and metal powder (Cr). Equiatomic CoCrCuFeNi microlattices with ∼170 µm diameter struts are then synthesized by H2-reduction of the oxides followed by sintering and interdiffusion of the resulting metals. These process steps are studied by in-situ synchrotron X-ray diffraction on single extruded microfilaments (lattice struts) with ∼250 µm diameter. After reduction and partial interdiffusion at 600 ˚C for 1 h under H2, filaments consist of lightly-sintered metallic particles with some unreduced Cr2O3. A reduced, nearly fully densified (porosity: 1.6 ± 0.7%)…

Liquid ink-printing followed by sintering is used to fabricate WC-Co microlattices and cutting tools. The microstructure of WC-xCo (x=0.5-20 wt.%) is studied for a range of carbide-to-binder ratios and for various sintering temperatures. For 0.5≤Co≤5 wt.%, struts in microlattices exhibit residual porosity due to incomplete densification, even at the highest sintering temperature of 1650 °C. With 10 wt.% Co, fully dense lattice struts are achieved after sintering at 1450 °C for 1 h. For 1450-1650 °C sintering temperatures, the hardness of WC-xCo struts initially increases (due to increasing densification with increased Co) and then gradually decreases (due to an increase…

Complex-shaped, finely-featured, ultra-high-melting ZrC/W composite structures were produced by coupling, for the first time, three-dimensional (3D) ink-extrusion printing with shape/size-preserving reactive melt infiltration (the Displacive Compensation of Porosity, DCP, process). Inks containing sub-micron WC powders were printed at ambient temperature into either fine-scale structures (sub-millimeter filaments) or into a larger-scale, finely-featured 3D structure (a centimeter-scale nozzle with a sub-millimeter-thick wall). After organic binder removal, the printed structures were sintered at 1650 °C for 1 h to achieve a porosity of 50%. The porous, rigid WC structures then underwent ambient pressure infiltration and reaction with Zr-Cu liquid at up to 1350…