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The PhD research of addresses several key aspects on the transport of inks in thin media, such as paper.

First, he considered ways to accurately quantify the co-solvent content present in paper. He also looked at the advantages and limitations associated with various measurement methods for determining co-solvent content. Thereafter, he explored methods to identify the key transport phenomena governing the behavior of co-solvents in paper. Finally, he looked at the physical properties that play a pivotal role in dictating the dynamics of processes such as imbibition, pore-fiber transport, and drying.

Experiments and simulations

To tackle these questions, Wang and his collaborators adopted an integrated approach in which experiments were combined with numerical simulations.

First, he used optical transmission and capacitive tomography to characterize imbibition and drying of model inks in paper.

Second, he studied the deformation of paper sheets after the deposition of aqueous co-solvent solutions, either through line deposition, spray deposition or complete immersion and subsequent drying.

Third, he developed a numerical model for the transport and drying process of co-solvent solutions in paper. And finally, he numerically and theoretically evaluated the possibility of quantification of liquid content by capacitance tomography.

Key findings

Wang found that in inkjet printing, liquid enters the inter-fiber pores first, causing a change in optical transmission. After that, it slowly migrates into smaller intra-fiber pores, leading to swelling of the paper.

This process is affected by several factors, for example the local water content, dimensions of the molecule of the ink components. Incorporating these phenomena, our numerical model reproduced the experimental results qualitatively well.

Title of PhD thesis: . Supervisors: Anton Darhuber and Federico Toschi.