2.1. Configuration of a 3D bioprinter for fabricating gel filaments
We modified the FDM printer for 3D biological printing through syringe loading and mechanical transmission. As shown in Figure 1a, the printer was controlled by the CS10-3 pulse generator and ZD-2HD542 driver. To extrude the biological ink in a stable manner, the 57HB76-401A stepper motor was installed on a customised frame to drive the syringe. The extrusion nozzle was connected to the FDM printer X-Y-Z mobile platform, which could realise the user’s customised printing structure. The extrusion velocities range from 0.5 to 10 mL/min out of a 17G (1-mm ID) dispensing needle. Before use, the needle was autoclaved at 121˚C, and the printing device was wiped with alcohol and irradiated with ultraviolet light 20-30min.