Investigation of the humidity control in the printing space for the material extrusion of medical biodegradable hydrogel

Materials extrusion for medical biodegradable hydrogel manifests potential for the fabrication of biomimetic functionalized tissues in tissue engineering. However, the uncontrollable shape of 3D printed structures usually leads to shrinkage as well as collapse of the prepared biocompatible scaffold, which limits the potential to develop large-size tissue or organs. Uncontrollable ambient humidity during the 3D printing process is a primary cause of the moisture loss and geometric variation of prepared architectures, which means the humidity in the printing space of hydrogel materials must be controlled accurately throughout the extrusion process. This study proposed a novel configuration of humidity-controlled atmospheric enclosure, by which the humidity distribution in the printing space can be accurately regulated. Subsequently, a fluid-thermal-humidity coupling field simulation model based on the finite element method was established to numerically investigate the humidity field in the printing space. Furthermore, printing trials were conducted with the proposed atmospheric enclosure, and the moisture loss of 3D architecture was avoided. The size of the scaffold was improved evidently from 25 mm(length) x 25 mm(width) x 0.6 mm(height) to 25 mm(length) x 25 mm(width) x 3.5 mm(height).