Optimization of a High Internal Phase Emulsion-Based Resin for Use in Commercial Vat Photopolymerization Additive Manufacturing

Fabrication of hierarchically porous trabecular bone replicas via 3D printing with high internal phase emulsions (HIPEs)

Combining emulsion templating with additive manufacturing enables the production of inherently porous scaffolds with multiscale porosity. This approach incorporates interconnected porous materials, providing a structure that supports cell ingrowth. However, 3D printing hierarchical porous structures that combine semi-micropores and micropores remains a challenging task. Previous studies have demonstrated that using a carefully adjusted combination of light absorbers and photoinitiators in the resin can produce open surface porosity, sponge-like internal structures, and a printing resolution of about 150µm. In this study, we explored how varying concentrations of tartrazine (0, 0.02, 0.04, and 0.08 wt%) as a light absorber affect the porous structure of acrylate-based polymerized medium internal phase emulsions fabricated via vat photopolymerization. Given the importance of a porous and interconnected structure for tissue engineering and regenerative medicine, we tested cell behavior on these 3D-printed disk samples using MG-63 cells, examining metabolic activity, adhesion, and morphology. The 0.08 wt% tartrazine-containing 3D-printed sample (008 T) demonstrated the best cell proliferation and adhesion. To show that this high internal phase emulsion (HIPE) resin can be used to create complex structures for biomedical applications, we 3D-printed trabecular bone structures based on microCT imaging. These structures were further evaluated for cell behavior and migration, followed by microCT analysis after 60 days of cell culture. This research demonstrates that HIPEs can be used as a resin to print trabecular bone mimics using additive manufacturing, which could be further developed for lab-on-a-chip models of healthy and diseased bone.

Effective and new technologies in kidney tissue engineering

Kidney disease encompasses a wide spectrum of conditions, ranging from simple infections to chronic kidney disease. When the kidneys are unable to filter blood and remove waste products, these abnormalities can lead to kidney failure. In severe cases of kidney failure, kidney transplantation is considered the only definitive treatment. Worldwide, the World Health Organization (WHO) repeatedly emphasizes the importance of organ donation and increasing transplantation rates. Many countries implement national programs to promote the culture of organ donation and improve patient access to kidney transplantation. The extent to which this procedure is performed varies across countries and is influenced by several factors, including the volume of organ donation, medical infrastructure, access to technology and health policies. However, a kidney transplant comes with challenges and problems that impact its success. Kidney tissue engineering is a new approach that shows promise for repairing and replacing damaged kidney tissue. This article reviews recent advances in kidney tissue engineering, focusing on engineered structures such as hydrogels, electrospinning, 3D bioprinting, and microfluidic systems. By mimicking the extracellular environment of the kidney, these structures provide suitable conditions for the growth and development of kidney cells. The role of these structures in the formation of blood vessels, the mimicry of kidney functions and the challenges in this field were also discussed. The results of this study show that kidney tissue engineering has high potential for treating kidney diseases and reducing the need for kidney transplantation. However, to achieve clinical application of this technology, further research is required to improve the biocompatibility, vascularization and long-term performance of engineered tissues.

3D printing stretchable and compressible porous structures by polymerizable emulsions for soft robotics

UV-curable 3D printing compositions for the fabrication of stretchable and flexible porous structures for soft robotics are presented. The stereolithography-based printing compositions are water-in-oil (W/O) emulsions in which water droplets are the pore-forming material, and the continuous phase is a stretchable polyurethane diacrylate (PUA). The porosity of the printed objects is controlled by the material's micro-porosity and by the macro-porosity obtained by a cellular design. The mechanical behavior can be tailored by the composition of the emulsion, providing both compliance and strength while utilizing a unique optimization methodology for fitting the ink to the 3D printer. This approach enables developing materials having superior mechanical properties, with the highest reported elongation-at-break for 3D printed porous structures, 450%. The emulsion-based printing compositions were utilized for fabricating a soft robotic gripper with unique actuation performance that could not be obtained with commonly used materials.

Investigating the Potential of Electroless Nickel Plating for Fabricating Ultra-Porous Metal-Based Lattice Structures Using PolyHIPE Templates

The use of polymerized high internal phase emulsions (polyHIPEs) as templates for electroless nickel plating is a promising method for producing ultra-porous metallic lattice structures with consistent wall thickness. These structures have desirable properties such as low density, high specific strength, resilience, and absorbency, making them suitable for various applications including battery electrodes, catalyst supports, and acoustic or vibration damping. This study aimed to optimize and investigate the electroless nickel plating process on polyHIPEs. Initially, a surfactant (Hypermer)-stabilized water-in-oil emulsion based on 2-ethylhexyl-acrylate and isobornyl-acrylate was used as a 3D printing resin to create polyHIPE structures. Then, the electroless nickel plating process was optimized using polyHIPE discs. The study also examined the effects of air, argon, and reducing atmospheres during the heating process to remove the polyHIPE template using metallized 3D-printed polyHIPE lattice structures. The findings indicated that different atmospheres led to the formation of distinct compounds. While nickel-coated polyHIPEs were fully oxidized in an air atmosphere, nickel phosphide (Ni3P) structures occurred in argon and reducing atmospheres along Ni metal. Moreover, in argon and reducing atmospheres, the porous structure of the polyHIPEs was retained as the internal structure was completely carbonized. Overall, the study demonstrated that intricate polyHIPE structures can be used as templates to create ultra-porous metal-based lattices for a wide range of applications.