Ferrofluids are suspensions of paramagnetic nanoparticles with a size of 5 to 15 nm. In this study, we investigated the effect of a permanent magnet on the shape and contact angle of a ferrofluid droplet on a superhydrophobic surface. We designed and built a test apparatus and prepared a superhydrophobic surface using a combination of laser and chemical treatment of the copper substrate. Measurements were carried out using a goniometer, and the results were processed with an image analysis program in the MATLAB environment. We measured the contact angle of the ferrofluid droplet and other parameters describing the droplet shape, such as the droplet height, the maximum droplet width, and the height of the droplet center. The measurements were performed at different distances of the magnet from the surface, orientations of the magnet, droplet volumes and concentrations of paramagenta nanoparticles. It is found that the shape and wetting angle of the droplet can be controlled by relative movement of the magnet.
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