Evaporation of superparamagnetic Colloids in magnetic fields

The evaporation of colloids droplets is a naturally abundant phenomenon, often used as a way to create deposits of self-assembled particles on a solid substrate. Recently, it has been shown that whiskey droplets do not present the wide-spread coffee-ring effect due to the presence of some tension-active agents combined with polymers adsorbing on the solid substrate. Moreover, it has also been found that modifying the shape of the particles creates capillary interactions among those particles and that these interactions can suppress the coffee-ring effect. In our work, we took advantage of magnetic interactions among superparamagnetic particles, along with the concentration of specific tension-active ions, to control the deposit’s pattern. We show in this presentation that the magnetic field can be used as a remote control for the deposit structures in the appropriate conditions.