In this article the dynamics of droplet absorption and penetration into papers are discussed. The experimental penetration data used in this study are derived from a measurement device consisting of a high-speed-camera, suitable microscope objectives and a piezoelectric droplet generator. This device allows studying the penetration of small, single ink droplets with realistic volumes in the range of few picoliters. The working principle of this unit is presented and it is shown that the resulting data can be used to investigate influences of different paper and ink properties on ink penetration. Both dye and pigment based aqueous inkjet inks as well as other fluids are included in this study. Furthermore, a model based on the Bosanquet differential equation is proposed to calculate ink penetration using structural parameters and properties of the materials used. The model also takes into account real and practical conditions, only limited fluid volumes relevant to the respective printing process are considered. Additionally, several coating layers and transitions between them can be analyzed. Model results are discussed and a comparison of the model and experimental observations is given. The model based on the Bosanquet equation is in good agreement with the measured penetration times which underlines the applicability of both the model and the measurement technique.
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