Experimental study of the impact of an ink-jet printed droplet on a solid substrate

This paper reports on an experimental study of the impact of water droplets on a solid substrate, with a droplet radius between 18 and 42 mum. We optically measured the interface shape during impact. The measured impact sequences show the impact phenomenology, droplet radius as a function of time, and oscillation behavior in the later stages of impact. The measured radius during impact is compared with existing models, and some of the deficiencies of common models are shown. The measured oscillation frequency in the later stage of impact compares well with an available analytical model. In addition, we measured the volume of the small bubble, which forms in the initial impact stage, as a function of impact velocity. The measured volume compares reasonably well with an approximate model based on air entrapment. (C) 2004 American Institute of Physics.