Operability diagram of drop formation and its response to temperature variation in a piezoelectric inkjet nozzle

The present study has focused on the operability diagram of drop formation and its response to temperature variation in an inkjet nozzle driven by a piezoelectric actuator. As an operating fluid, ethylene glycol was used, and square wave pulses were applied to the nozzle in the present experiments. The operability diagram was constructed in driving voltage and pulse width space by changing the operating temperature from 30 °C to 50 °C. Four distinct types of drop response have been uncovered and are summarized in the operability diagram. The four types of response include single primary drop formation, drop formation with satellites, nozzle wetting without drop formation, and emission of a random spray. From the operability diagram, W-shaped regime of single primary drop was found, which was enlarged as temperature increased. Furthermore, the time scale of the W-shaped regime is closely related to the optimal pulse width and meniscus oscillation period of the present inkjet nozzle. In addition, it was found that by increasing the driving voltage and temperature, the size of single primary drop is increased due to the reduction in viscosity and contact angle of the operating liquid.