Device for printing droplet or ink on substrate or paper

A device for printing a droplet onto a substrate, the device comprising:

• a droplet generating member which is needle-shaped and comprises:
• a receiving portion disposed vertically to receive a solution;
• and
• a discharge hole connected to the receiving portion and formed on the bottom of the receiving portion so that the solution can be discharged from the receiving portion;
• a substrate disposed below the droplet generating member, the substrate includes a target portion to which the droplet discharged from the discharge hole of the droplet generating member is dropped and attached;
• a voltage applier which applies a voltage to the droplet so that the droplet can be dropped onto the target portion of the substrate;
• a volume measuring unit which measures the volume of the droplet while it hangs from the droplet generating member;
• and
• a droplet control unit which maintains the volume of the droplet at a predetermined level based on the measured volume of the droplet,
• wherein the droplet control unit increases or decreases compression in the solution in the receiving portion according to a signal from the volume measuring unit.