US Patent 7611218 Inkjet printhead that prints keep-wet dots to avoid clogging

An inkjet printhead with a plurality of nozzles, a heater element adjacent each of the nozzles respectively for heating an ejectable liquid to form a gas bubble that causes the ejection of a drop of the ejectable liquid from the nozzle, and, a print engine controller for controlling the operation of the heater elements. During use, the print engine controller ensures that the time interval between successive actuations of each of the heater elements is less than a predetermined time in which the viscosity of the ejectable liquid at the nozzle increases to a threshold, known as the decap time.