Provided are a cell culture compartment unit and an array including the same. A spring located within the housing urges the shield in a distal needle covering direction and a locking member also provided inside the housing moves simultaneously with the shield during injection and automatically locks the shield in a position where the sharp end of the needle cannula is concealed thereby irreversible immobilizing the safety needle assembly. A controller selectively switches the mechanism between its first and its second states such that ink droplets of the predetermined large volume are not simultaneously emitted from adjacent ones of the nozzles.