Rheological behavior of Al2O3 suspensions containing polyelectrolyte complexes for direct ink writing

Hierarchical Porous Ceramics with Distinctive Microstructures by Emulsion-Based Direct Ink Writing

Hierarchical porous materials are ubiquitous in nature and have inspired the fabrication of cellular structures for a multitude of applications. As an extrusion-based 3D printing technique, direct ink writing (DIW) allows for customizable design and accurate control of printed structures. Recently, its combination with colloidal processing methods used for bulk porous ceramics, such as emulsion templating, has further extended its capability of fabricating porous ceramics across multiple length scales. In light of the recent development, the ink formulation for emulsion-based DIW can be further explored, and there is still a need for a better understanding of the structure-property relationship. Herein, we introduce two types of gelling additives, i.e., poly(ethylenimine) (PEI) and Pluronic F-127, respectively, into particle-stabilized emulsions and fabricate hierarchical porous alumina lattices by DIW. We discover that the two gelling additives can lead to distinctive microstructures due to their different gelling mechanisms. Moreover, the 3D printed hierarchical porous ceramic lattices are found to exhibit a potential energy absorption property. The effects of ink formulations, including gelling additives and solid loading, on ink rheology, microstructure, and mechanical properties are investigated. The 3D printed hierarchical porous ceramic lattices exhibit a high average porosity of 73.7%-79.3% with an average compressive strength of 1.53-9.61 MPa and a specific energy absorption of 0.33-2.67 J/g. Featuring two distinctive microstructures with tunable structural features and mechanical properties, the 3D printed hierarchical porous ceramics in this study have potential in many applications, including lightweight structures, tissue engineering scaffolds, filtration, etc.

Unconventional Application of Direct Ink Writing: Surface Force-Driven Patterning of Low Viscosity Inks

A new concept for the direct ink writing (DIW) of model titanium dioxide inks through capillary action (no applied pressure during printing) is investigated through the use of diluted low viscosity inks for micropatterning. The inks are characterized with respect to rheological, thermal, and surface properties. Printed structures are characterized by profilometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and photocatalytic degradation of methylene blue. By use of the concept of surface force-driven DIW and by control of the writing speed and ink composition for different substrate surfaces, the heights of profiles of printed structures can be tailored from under 100 nm to over 1 μm. Furthermore, it is demonstrated that the surface roughness of the titanium dioxide films can be reduced up to 60% by increasing writing speed and line-to-line spacing. This work highlights a new concept of low viscosity solution micropatterning that currently can only be performed by other methods such as inkjet printing. It is believed that this novel approach will hold the key to patterning a range of low viscosity inks for various thin film technological applications.

3D Printing for the Clinic: Examining Contemporary Polymeric Biomaterials and Their Clinical Utility

The advent of additive manufacturing offered the potential to revolutionize clinical medicine, particularly with patient-specific implants across a range of tissue types. However, to date, there are very few examples of polymers being used for additive processes in clinical settings. The state of the art with regards to 3D printable polymeric materials being exploited to produce novel clinically relevant implants is discussed here. We focus on the recent advances in the development of implantable, polymeric medical devices and tissue scaffolds without diverging extensively into bioprinting. By introducing the major 3D printing techniques along with current advancements in biomaterials, we hope to provide insight into how these fields may continue to advance while simultaneously reviewing the ongoing work in the field.

Ceramic Robocasting: Recent Achievements, Potential, and Future Developments

Additive manufacturing (AM) of ceramic materials has attracted tremendous attention in recent years, due to its potential to fabricate suitable advanced ceramic structures for various engineering applications. Robocasting, a subset of ceramic AM, is an ideal technique for constructing fine and dense ceramic structures with geometrically complex morphology. With the freedom and convenience to deposit various materials within any 3D spatial position, ceramic robocasting opens up unlimited opportunities, which are otherwise hardly attainable from other AM techniques. Here, a summary of the recent progress on the fabrication of single and multi-ceramic structures by robocasting is provided, as well as the prospects of achieving shapeable ceramic structures. The current challenges in ceramic robocasting and an outlook on its development, especially toward the fabrication of self-shaping ceramic structures, are also discussed.

3D printed dielectric ceramic without a sintering stage

This paper presents for the first time the fabrication of dielectric ceramic parts by 3D printing without sintering. The printable paste was prepared by mixing a carefully selected amount of water-soluble Li₂MoO₄ powder with water. A viscous mixture of solid ceramic particles and saturated aqueous phase was formed with a solid content of 60.0 vol.%. Printing of the sample discs was conducted with material extrusion using a low-cost syringe-style 3D printer. The consolidation and densification of the printed parts occurred during both printing and drying of the paste due to extrusion pressure, capillary forces, and recrystallization of the dissolved Li₂MoO₄. Complete drying of the paste was ensured by heating at 120 °C. The microstructure showed no delamination of the printed layers. Relatively high densities and good dielectric properties were obtained, especially when considering that no sintering and only pressure from the extrusion was employed. This approach is expected to be feasible for similar ceramics and ceramic composites.