Bubble Nucleation Pulse-Width in Thermal Inkjet Actuators

Abstract Thermal inkjet actuators operate by passing a current through an electrical resistor, the heater, in contact with a working liquid such as ink. This heats the liquid rapidly (dT/dt≈108−109 K/s), and once the liquid temperature exceeds the superheat limit, it flash-boils. The resultant high temperature (≈300 °C) and pressure (≈10 MPa) bubble expands, forcing the ink through a nozzle, forming a droplet which then travels through the print gap until it strikes the media. Here, we discuss the bubble nucleation criterion for thermal inkjet technology, using numerical and analytical models. The results from the different models, and data from bubble visualization and droplet weight experiments, are within approximately 10% of each other. The experimental data provide a useful benchmark for comparison against other theoretical models. The newly derived analytical model provides a simple method for the thermal inkjet designer to estimate the bubble nucleation pulse-width and the energy required for nucleation.