Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces
AbstractEvaluation of superhydrophobic (SH) surfaces based on contact angle measurements is challenging due to the high mobility of drops and the resolution limits of optical goniometry. For this reason, some alternatives to drop-shape methods have been proposed such as the damped-oscillatory motion of ferrofluid sessile drops produced by an external magnetic field. This approach provides information on surface friction (lateral/shear adhesion) from the kinetic energy dissipation of the drop. In this work, we used this method to compare the low adhesion of four commercial SH coatings (Neverwet, WX2100, Ultraever dry, Hydrobead) formed on glass substrates. As ferrofluid, we used a maghemite aqueous suspension (2% v/v) synthesized ad hoc. The rolling magnetic drop is used as a probe to explore shear solid–liquid adhesion. Additionally, drop energy dissipates due to velocity-dependent viscous stresses developed close to the solid–liquid interface. By fitting the damped harmonic oscillations, we estimated the decay time on each coating. The SH coatings were statistically different by using the mean damping time. The differences found between SH coatings could be ascribed to surface–drop adhesion (contact angle hysteresis and apparent contact area). By using this methodology, we were able to grade meaningfully the liquid-repelling properties of superhydrophobic surfaces. View Full-Text
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Goncalves Dos Santos, A.; Montes-Ruiz Cabello, F.J.; Vereda, F.; Cabrerizo-Vilchez, M.A.; Rodriguez-Valverde, M.A. Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces. Coatings 2019, 9, 270.
Goncalves Dos Santos A, Montes-Ruiz Cabello FJ, Vereda F, Cabrerizo-Vilchez MA, Rodriguez-Valverde MA. Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces. Coatings. 2019; 9(4):270.Chicago/Turabian Style
Goncalves Dos Santos, Angelica; Montes-Ruiz Cabello, Francisco J.; Vereda, Fernando; Cabrerizo-Vilchez, Miguel A.; Rodriguez-Valverde, Miguel A. 2019. "Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces." Coatings 9, no. 4: 270.
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