Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone

Personalized 3D printed bone scaffolds: A review

3D printed bone scaffolds have the potential to replace autografts and allografts because of advantages such as unlimited supply and the ability to tailor the scaffolds' biochemical, biological and biophysical properties. Significant progress has been made over the past decade in additive manufacturing techniques to 3D print bone grafts, but challenges remain in the lack of manufacturing techniques that can recapitulate both mechanical and biological functions of native bones. The purpose of this review is to outline the recent progress and challenges of engineering an ideal synthetic bone scaffold and to provide suggestions for overcoming these challenges through bioinspiration, high-resolution 3D printing, and advanced modeling techniques. The article provides a short overview of the progress in developing the 3D printed scaffolds for the repair and regeneration of critical size bone defects. STATEMENT OF SIGNIFICANCE: Treatment of critical size bone defects is still a tremendous clinical challenge. To address this challenge, diverse sets of advanced manufacturing approaches and materials have been developed for bone tissue scaffolds. 3D printing has sparked much interest because it provides a close control over the scaffold's internal architecture and in turn its mechanical and biological properties. This article provides a critical overview of the relationships between material compositions, printing techniques, and properties of the scaffolds and discusses the current technical challenges facing their successful translation to the clinic. Bioinspiration, high-resolution printing, and advanced modeling techniques are discussed as future directions to address the current challenges.

Binder Jetting of Custom Silicone Powder for Direct Three-Dimensional Printing of Maxillofacial Prostheses

Recent advances in digital workflow have transformed clinician's ability to offer patient-specific devices for medical and dental applications. However, the digital workflow of patient-specific maxillofacial prostheses (MFP) remains incomplete, and several steps in the manufacturing process are still labor-intensive and are costly in both time and resources. Despite the high demand for direct digital MFP manufacturing, three-dimensional (3D) printing of colored silicone MFP is limited by the processing routes of medical-grade silicones and biocompatible elastomers. In this study, a binder jetting 3D printing process with polyvinyl butyral (PVB)-coated silicone powder was developed for direct 3D printing of MFP. Nanosilica-treated silicone powder was spray dried with PVB by controlling the Ohnesorge number and processing parameters. After printing, the interconnected pores were infused with silicone and hexamethyldisiloxane (HMDS) by pressure-vacuum sequential infiltration to produce the final parts. Particle size, coating composition, surface treatment, and infusion conditions influenced the mechanical properties of the 3D-printed preform, and of the final infiltrated structure. In addition to demonstrating the feasibility of using silicone powder-based 3D printing for MFP, these results can be used to inform the modifications required to accommodate the manufacturing of other biocompatible elastomeric materials.

Processability of a Hot Work Tool Steel Powder Mixture in Laser-Based Powder Bed Fusion

Powder bed fusion of metals using a laser beam system (PBF-LB/M) of highly complex and filigree parts made of tool steels is becoming more important for many industrial applications and scientific investigations. To achieve high density and sufficient chemical homogeneity, pre-alloyed gas-atomized spherical powder feedstock is used. For high-performance materials such as tool steels, the number of commercially available starting powders is limited due to the susceptibility to crack formation in carbon-bearing steels. Furthermore, scientific alloy development in combination with gas-atomization is a cost-intensive process which requires high experimental effort. To overcome these drawbacks, this investigation describes the adaption of a hot work tool steel for crack-free PBF-LB/M-fabrication without any preheating as well as an alternative alloying strategy which implies the individual admixing of low-cost aspherical elemental powders and ferroalloy particles with gas-atomized pure iron powder. It is shown that the PBF-LB/M-fabrication of this powder mixture is technically feasible, even though the partly irregular-shaped powder particles reduce the flowability and the laser reflectance compared to a gas-atomized reference powder. Moreover, some high-melting alloying ingredients of the admixed powder remain unmolten within the microstructure. To analyze the laser energy input in detail, the second part of the investigation focuses on the characterization of the individual laser light reflectance of the admixed alloy, the gas-atomized reference powder and the individual alloying elements and ferroalloys.

Optimization of the Projection Microstereolithography Process for a Photocurable Biomass-Based Resin

Biomass materials, an important source of chemical feedstocks, could replace fossil fuels as a resource in the future. The chemical feedstocks from biomass materials are used in many medical and pharmaceutical products and in fuels, chemicals, and functional materials. Biomass materials are expected to be used in biomedical engineering fields, especially due to their low biotoxicity. By the way, most of the demand for bio-application fields is an application targeted for customized production, so a high formability is required for production. Research on three-dimensional (3D) printing technology capable of satisfying these requirements has been ongoing. Manufacturing additives need to be investigated to use biomass materials as a resin or bioink safely for 3D printing, which is a technique widely used in biomedical engineering fields. In this study, a projection microstereolithography (PμSL) system, a 3D printing technique, was made that uses a biomass-based resin. Biomass materials are designed to be photocurable for use in the PμSL process. Various PμSL process parameters were investigated using the biomass-based resin to determine the optimum fabrication conditions for 3D structures. This study demonstrated that a biomass-based resin can be used in the PμSL process. We provide a method for its application in various biomedical engineering fields.

3D Printing Low-Stiffness Silicone Within a Curable Support Matrix

Embedded 3D printing processes involve extruding ink within a support matrix that supports the ink throughout printing and curing. In once class of embedded 3D printing, which we refer to as "removable embedded 3D printing," curable inks are printed, cured, then removed from the uncured support matrix. Removable embedded 3D printing is advantageous because low-viscosity inks can be patterned in freeform geometries which may not be feasible to create via casting and other printing processes. When printing solid-infill geometries, however, uncured support matrix becomes trapped within the prints, which may be undesirable. This study builds on previous work by formulating a support matrix for removable embedded 3D printing that cures when mixed with the printed silicone ink to solve the problem of trapped, uncured support matrix within solid-infill prints. Printed specimens are shown to have a nearly isotropic elastic modulus in directions perpendicular and parallel to the printed layers, and a decreased modulus and increased elongation at break compared to specimens cast from the ink. The rheological properties of the support matrix are reported. The capabilities of the printer and support matrix are demonstrated by printing a variety of geometries from four UV and addition-cure silicone inks. Shapes printed with these inks range by nearly two orders of magnitude in stiffness and have failure strains between approximately 50 and 250%, suggesting a wide range of potential applications for this printing process.