Influence of magnetic nanoparticle diameter on three-layer MEMS actuation via Casimir and hydrodynamic forces

Here, we investigate the dynamical response of a three-layer microsystem, with a ferrofluid as the intervening layer, to variations in the optical properties of the interacting components under the influence of Casimir and hydrodynamic forces. It is shown that increasing the magnetic nanoparticle diameter, for a fixed nanoparticle concentration, leads to an increase in the Casimir force. Hence, the performance sensitivity of the system has been studied for various diameters of the nanoparticles across different concentrations. Furthermore, it is explored how to achieve a condition in which the ferrofluid has no influence on the magnitude of the Casimir force by adjusting the nanoparticle diameters to a critical value. The dependence of the latter on the nanoparticle concentration at different separations between the components of the three-layer microsystem has also been explored. Subsequently, the impact of nanoparticle diameter on the phase space trajectories of the microsystem and the effect of different velocities of the moving parts have also been investigated. As a result, it has been demonstrated that an increment of the nanoparticle diameter leads to a higher probability of adhesion, also known as stiction, between the moving microsystem components. Finally, in driven microsystems, under the influence of a time dependent periodic external force, the change of the nanoparticle diameter not only affects the adhesion of the moving components but also significantly influences the stable periodic working range of the microsystem for both high and low driven frequencies.