Focused spray jet printing system

A focused spray jet printing system, comprising:

• an atomization unit which atomizes ink by a carrier gas to generate atomization droplets;
• a head unit including a virtual impactor which uniformizes sizes of the atomization droplets generated from the atomization unit and ejects the uniformized atomization droplets;
• a focusing unit provided in the head unit, configured to focus the uniformized atomization droplets using sheath gas supplied to the focusing unit, and configured to spray the focused atomization droplets onto a substrate;
• a sheath gas mass flow controller (sheath MFC) which supplies the sheath gas to the focusing unit;
• and
• a valve unit which is selectively connected to any one of an atomization droplet flow path which is formed in the head unit to flow the uniformized atomization droplets and a flow path formed at the outside of the head unit to flow the sheath gas, wherein the atomization droplet flow path connects the virtual impactor and the focusing unit,
• wherein the head unit includes a vent flow path which is connected to the atomization droplet flow path and the valve unit,
• the system further comprising:
• a vent mass flow controller (vent MFC),
• wherein the vent MFC is connected to the vent flow path by the valve unit in the case of printing-off such that the vent MFC vents the uniformized atomization droplets and a part of the sheath gas outside,
• wherein the focusing unit includes a nozzle at a lower end thereof, and the sheath MFC supplies a flow rate of the sheath gas more than a flow rate of the sheath gas used to focus the uniformized atomization droplets in the case of printing-on in which the uniformized atomization droplets are sprayed from the nozzle,
• wherein a flow rate of a discharged fluid sprayed from the nozzle in the case of printing-on in which the uniformized atomization droplets are sprayed from the nozzle is equal to a flow rate of the discharged fluid sprayed from the nozzle in the case of printing-off in which the uniformized atomization droplets are not sprayed,
• wherein in the case of printing-on, the discharged fluid includes both the uniformized atomization droplets and the sheath gas, and in the case of printing-off, the discharged fluid includes only the sheath gas, and
• wherein a set flow rate of the vent MFC is less than a flow rate of the sheath gas supplied by the sheath MFC, and is more than a flow rate of the uniformized atomization droplets supplied to the focusing unit.