High-frequency electrohydrodynamic printing

A method of increasing the jetting frequency of an electrohydrodynamic printer, the method comprising:

• charging printing fluid in a nozzle of the printer using an electrode at a first electrical potential;
• and
• forming an extraction field between the electrode and an electrically conductive surface spaced from the electrode by a gap, an extraction opening of the nozzle being located in the extraction field so that charged printing fluid is extracted from the nozzle through the extraction opening for deposition on a printing surface,
• wherein at least one of the following is located in the gap when the extraction field is present:
• non-conductive printing fluid, non-conductive material of the nozzle, a dielectric gas, and a layer of cleaning fluid flowing along the electrically conductive surface.

An electrohydrodynamic printer, comprising:

• a nozzle having an extraction opening, the printer being configured to provide printing fluid in the nozzle and at the extraction opening;
• and
• an electrode configured to operate at a first electrical potential to charge the printing fluid in the nozzle and to form an extraction field between the electrode and an extraction surface at a second electrical potential with the extraction opening in the extraction field, whereby charged printing fluid is extracted from the nozzle by the extraction field through the extraction opening for deposition on a printing surface,
• wherein the electrode is inside the nozzle such that an end of the electrode closest to the extraction opening is immersed in the printing fluid in the nozzle.