Droplet ejection performance of a monolithic thermal inkjet print head

Abstract

This paper presents a simulation study of the droplet ejection performance of a thermal inkjet print head. The geometry of the print head comprises a dome-shaped ink chamber, a nozzle guide and a ring-shaped heater integrated on each chamber. The design eliminates direct contact between the heater and the ink, thus minimizing heater burnout. The ink manifold, ink chamber and nozzle are aligned, thus facilitating higher nozzle density. The model simulates thermal bubble dynamics including nucleation and growth of thermal bubbles caused by a thermal pulse. The model was validated by comparing model predictions with experimental results for a previously reported print head design. Then, the model was used to simulate the droplet ejection performance of the proposed inkjet print head. Effects of print head geometry including nozzle diameter, nozzle length, chamber size, heater dimensions and location, thermal conductivity of the passivation layer, operating conditions including total thermal energy and pulse width, properties of the ink including density, viscosity and surface tension on the performance of the inkjet device are investigated. The influence of these parameters on the drop volume and velocity, threshold energy and tail length of the ejected droplets is studied.