Air bubbles entrapped in the ink channel are a major problem in piezo-driven inkjet printing. They grow by rectified diffusion and eventually counteract the pressure buildup at the nozzle, leading to a breakdown of the jetting process. Experimental results on the droplet velocity udrop as a function of the equilibrium radius R0 of the entrained bubble are presented. Surprisingly, udrop(R0) shows a pronounced maximum around R0 = 17 μm before it sharply drops to zero around R0 = 19 μm. A simple one-dimensional model is introduced to describe this counterintuitive behavior which turns out to be a resonance effect of the entrained bubble.
de Jong, J., Jeurissen, R., Borel, H., van den Berg, M., Wijshoff, H., Reinten, H., ... Lohse, D. (2006). Entrapped air bubbles in piezo-driven inkjet printing: Their effect on the droplet velocity. Physics of fluids, 18(12), . https://doi.org/10.1063/1.2397015