Investigation of the temperature gradient control in the printing space for the material extrusion of medical biodegradable hydrogel.

Material extrusion has shown promise in the fabrication of biocompatible scaffolds for tissue engineering using medical biodegradable hydrogel materials. However, the uncontrollable shape of prepared 3D architecture decelerates the development of large-size complex hydrogel models for the fabrication of human-scale tissue or organs. A primary cause of the collapse as well as shrinkage of prepared architectures is the uncontrollable ambient temperature distribution during the extruding process for hydrogel materials. Therefore, there is a need to accurately control the temperature gradient in the printing space during the material extrusion. The study proposed a novel temperature-controlled substrate configuration with a multilayered enclosure, by which the temperature gradient in the printing space can be regulated by varying the height as well as the internal diameter of the enclosure. Subsequently, a finite element simulation model, as well as a self-developed temperature measuring device, was established to numerically and experimentally investigate the temperature distribution in the printing space. Furthermore, printing trials were implemented on the novel substrate. The collapse of 3D architectures was successfully avoided, and the height of scaffolds was improved obviously from 2.21 mm to 13.24 mm.