Magneto-induced surface morphologies in magnetorheological elastomer films: An analytical study
In this paper, we develop a three-dimension semi-infinite mesoscopic model to analyze the surface micro-deformation of the MRE films under external magnetic fields. By considering the matrix of MRE films as an infinite continuous solid with absolutely smooth surfaces, we firstly analyze the surface morphologies induced by a magnetized particle and a magnetized particle pair. Following the superposition principle, we then derive an analytical solution based on an explicit discrete particle distribution to reveal the surface morphology changes resulting from many-magnetized-particle interactions. The theoretical analysis demonstrates that the particle distributions and concentrations play a key role in the formation of surface microstructures. The magneto-induced morphologies such as bump-like, concave-like and the mountain-like microstructures are predicted by the model which are closely related with the manners of particle arrangement inside the matrix. However, the particle magnetization intensity and the matrix modulus only have an influence on the amplitudes of the surface displacement. Several magneto-induced surface configurations are presented and discussed to show how we can control the surface of MRE films to make them having tunable properties in friction, wettability and adhesion. In addition, by averaging the magnetic induced surface displacement, the proposed model gives an excellent agreement with the dipole magnetostrictive theory. Moreover, we found that for an inherent hydrophobic material (contact angle >90°), the anisotropic MRE films with column-structured particles could become super-hydrophobic (contact angle >160°) when a moderate magnetic field is applied.