A review on the challenges of 3D printing of organic powders

3D printing technologies have enabled advances in biomedical research and development, including rapid fabrication of complex, customised constructs for personalised treatment of patients. However, there are still limitations with the 3D printing technologies in relation to the diversity of biomaterials, and the versatility of the printing methods to print such diverse materials. While many materials have been used for biomedical applications involving high load bearing forces, e.g. ceramics and metals, they struggle in areas of biodegradability, and supporting tissue adhesion. An alternative are natural polymers, which are currently being investigated in the biomedical industry and are generally biocompatible, biodegradable and bioactive. However, they lack optimal mechanical properties necessary for high load bearing applications. Natural polymers in a powdered form, also referred to as organic powders, can allow for much denser and higher integrity constructs compared to their more common bioink counterparts, whilst maintaining many of the desired biological attributes. However, many organic powders are either do not respond to light and degrade in heat, preventing their use in many light and thermal based 3D printing processes. Powder inkjet printing is a 3D printing technology that utilizes an alternative means of solidifying the powdered material. These include physical or chemical bonding, instead of photopolymerisation, melting or sintering via the exposure of heat or light. Nevertheless, the binders or solutions that are commonly used with organic powders are high in acidity which can damage the printer components, further limiting this materials printability. This paper investigates the current 3D printing technologies that can print with biomaterials. Several elements are investigated, including current biomedical applications, fusion technology, material limitations and useable biomaterials. In addition to the printing processes, a study on available biomaterials, in particular organic powders, is elaborately discussed. The origins of the biomaterials are explored, in addition to the acceptable 3D printers, current applications, and printable forms. The limitations found with the current available printing processes is also discussed, in relation to their compatibility with organic powders, and their required binder solutions.