Effects of actuating waveform,ink property,and nozzle size on piezoelectrically driven inkjet droplets

Computational fluid dynamics and micro-flow visualization (μ-FV) have been complementarily performed to study the evolution of a single droplet ejected from a bend-mode piezoelectric inkjet printhead. The numerical simulation is characterized by the coupled piezoelectric-structural-fluid solution procedure and verified by the μ-FV results. The in-house numerical code is subsequently applied to investigate the influences of electric voltage φ _pp, pulse shape, ink property, and nozzle diameter D _n on the droplet volume, velocity, and configurations. φ _pp studied ranges from 14 to 26 V and pulse shape is explored by varying the key time intervals with fixed voltage slopes. The influence of ink property is examined by investigating the dynamic viscosity μ and surface tension σ separately. Investigation on the effects of nozzle diameter is also conducted by decreasing D _n from 26 to 11 at 3 μm interval. The computed results are found in good agreement with the experimental ones. New findings are to discover the critical ranges of electric waveform parameters, μ, and σ outside which the phenomena of satellite droplets and puddle formation at the nozzle opening are absent. In addition, the imbedded physical rationales for these critical ranges are provided. The results are also new in terms of the identifications of the critical σ and D _n for the reference of improving the droplet quality.