Direct ink writing of polycaprolactone / polyethylene oxide based 3D constructs

There has been increasing interest over recent years in the application of three-dimensional (3D) printing technologies in the biomedical field. One such method is Direct Ink Writing (DIW); this approach has the potential advantage of allowing room-temperature deposition of materials, presented as an ink, to build complex architectures. DIW offers the ability to process biomaterials containing temperature-sensitive components. Due to the fabrication principles of DIW, there are specific rheological requirements that the ink must exhibit for the 3D construction. For this reason, hydrogel-based liquid feed stocks have been the focal point of ink development. As a consequence, studies based on inks comprising hydrophobic biomaterials, which are insoluble in water and hence unsuited to the hydrogel approach, have been limited. In this study, we investigate novel inks that utilize polycaprolactone (PCL), a hydrophobic polymer, as the primary constituent by dissolving the polymer in solvent systems based on dichloromethane (DCM) and acetone (ACE). Moreover, polyethylene oxide (PEO) was incorporated into the PCL systems in order to extend the range of hydrophilicity of the systems. The rheological properties of the inks were investigated as a function of polymer composition and solvent system. Woodpile constructs of PCL and PCL/PEO were fabricated using DIW method and were assessed by a series of material characterisation. The type of solvent system had a noticeable impact on the ink rheology, which ultimately affected the surface properties. The incorporation of PEO particularly enhanced the roughness and wettability of the constructs. Our results support the use of DIW as a new means to process hydrophobic polymers for biomedical applications.