3D-printing porosity: A new approach to creating elevated porosity materials and structures

Abstract

Porosity plays an essential role in the performance and function of biomaterials, tissue engineering, and clinical medicine. For the same material chemistry, the level of porosity can dictate if it is cell, tissue, or organ friendly; with low porosity materials being far less favorable than high porosity materials. Despite its importance, it has been difficult to create three-dimensionally printed structures that are comprised of materials that have extremely high levels of internal porosity yet are surgically friendly (able to handle and utilize during surgical operations). In this work, we extend a new materials-centric approach to 3D-printing, 3D-Painting, to 3D-printing structures made almost entirely out of water-soluble salt. The structures are then washed in a specific way that not only extracts the salt but causes the structures to increase in size. With the salt removed, the resulting medical polymer structures are almost entirely porous and contain very little solid material, but the maintain their 3D-printed form and are highly compatible with adult human stem cells, are mechanically robust enough to use in surgical manipulations, and can be filled with and act as carriers for biologically active liquids and gels. We can also extend this process to three-dimensionally printing other porous materials, such as graphene, metals, and even ceramics.

Reviewing recently developed technologies to direct cell activity through the control of pore size: From the macro‐ to the nanoscale

“…Chondrocytes resulted more infiltrated into scaffolds prepared using high concentrations of ice particulates while they deposited on the surface of the control with less interconnected pores. Hierarchical structures for tissue engineering applications were also recently realized by several groups (Chen et al, ; Hu et al, ; Jakus et al, ; Kim et al, ; Morgan et al, ; Novotna et al, ; Prakasam et al, ; Sherborne et al, ). Jakus et al (), for example, used the 3D‐painting process, a new form of 3D‐printing combined with salt leaching.…”

“…Hierarchical structures for tissue engineering applications were also recently realized by several groups (Chen et al, ; Hu et al, ; Jakus et al, ; Kim et al, ; Morgan et al, ; Novotna et al, ; Prakasam et al, ; Sherborne et al, ). Jakus et al (), for example, used the 3D‐painting process, a new form of 3D‐printing combined with salt leaching. Like fused deposition modeling, this new method extrudes fused thermoplastic polymers through a nozzle to build complex structures through a layer‐by‐layer approach directly from a CAD model (Masood, ).…”

“…The difference with 3D‐printing technique is the material processed, made almost entirely out of water‐soluble salt. The resulting polymeric structures are highly porous and contain a low percentage of solid material (Jakus et al, ). More specifically, authors synthetized a 3D‐printable ink using PLGA and a water‐soluble salt as porogen; then the salt was dissolved and removed from the printed structure, obtaining a multiscale pore architecture formed by controlled macropores and interconnected micropores on the filaments surface (F‐PLGA).…”

“…Several techniques have been adopted to optimize the manufacturing and modelling of structures with controlled, engineered pore size across a variety of length scales. They include conventional fabrication techniques such as salt leaching, gas foaming, phase separation, freeze‐drying, freeze‐casting, solid‐state porogen thermal decomposition, cell encapsulation, electrospinning (Jakus et al, ; Kundu, Rajkhowa, Kundu, & Wang, ; Loh & Choong, ). Nonetheless, these traditional methods do not allow to obtain a precise control of scaffold architecture and to achieve reproducible size and shape of pores (Danilevicius et al, ; Salerno, Di Maio, Iannace, & Netti, ).…”

3D Printing and Digital Processing Techniques in Dentistry: A Review of Literature

“…PLGA has been used as a suitable material for fabricating the biodegradable microspheres since its safety in clinical applications has been well confirmed . Further, medical grade PLGA has been widely used for biomaterial 3D‐printing work previously while maintaining the 3D‐printed structure . From the aspect of biomedicine, it offers broad application prospects and deserves further research and development.…”