Abstract :
[en] Evaporation of sessile colloidal droplets is a way to organize suspended particles. It is already
known that the composition of the surrounding fkuid modi es the dried deposit. For superparamagnetic particles, recent studies showed that external magnetic fi elds can act as remote controls for those deposits. In this paper, we study the confi guration space given by the interplay of such fi elds and a modi cation of the fluid composition by considering various concentrations of phosphate buffered saline (PBS). We show that the magnetic fi eld modifi es the morphological properties of the deposit, while the composition (i.e. PBS concentration) modifi es the density profi le of the deposit. We then present an explanation of these influences considering the competition between (i) sedimentation, (ii) coffee-ring and (iii) Marangoni flows. From these considerations, we propose a master curve which should be able to model the deposit densities of any system where the above mechanisms compete with each other.
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