Simulations And Experiments Of Magnetically Actuated Micro-rotating Stages Supported On Single Liquid Droplet

With the development of MEMS technology,the micro-rotating stages have made rapid development.For the micro-rotating stages supported on solid bearing,it’s difficult to avoid the influence of solid-solid friction.In addition,the micro-rotating stages supported on gas bearing or contactless bearing require complicated manufacture processes with tight fabrication tolerances and complex control schemes.Micro-rotating stages supported on liquid bearing can eliminate solid-solid friction,and enhance flexibility.Thus,it has great significance to do research on micro-rotating stages supported on liquid bearing.Here,the theoretical and simulation model is established for the magnetically actuated micro-rotating stages supported on single liquid droplet.The influence of different parameters on the loading capacity,motion performance and anti-interference performance is studied in this paper.Experiment system is built and experimental analysis and verification are also presented.First,on the basis of the structure of single liquid droplet,free-type and restrictedtype of the micro-rotating stages are proposed respectively.Based on Young-Laplace equation,numerical iteration is used to obtain the profile of the liquid bridge,then the capillary force is calculated.Based on Surface Evolver,the finite elements simulation model is established.Then the result obtained from finite elements method is compared with the result from Young-Laplace equation method.The evaluation indexes of the loading capacity are also proposed,and the influence of different parameters on the loading capacity of the micro-rotating stages of two structures is analyzed respectively.Additionally,the two structures are compared with each other.Secondly,based on the Helmholtz coil principle,the control method for generating the rotating magnetic field around arbitrary axis is derived.Based on COMSOL Multiphysics,the simulation model of the rotating magnetic field is established,and the magnetic moment applied to the micro-rotating stage is analyzed.The fluid friction model for the micro-rotating stage is built to analyze the influence of viscosity and rotation frequency on the friction resistance moment.Combined with the magnetic moment and the fluid friction moment,the maximum rotation frequency of the micro-rotating stage is also analyzed.On the basis of theoretical model of the liquid bridge,the anti-interference performance is studied in three aspects: anti-stretch,anti-shear and anti-roll.At last,the capillary experiment and rotation experiment of the micro-rotating stages supported on single liquid droplet are carried out respectively.The capillary force exerted on the micro-rotating stages is measured experimentally,and the experimental results show good agreement with the simulation result.The motion performance test system of the micro-rotating stages is also established.The motion performance of the micro-rotating stages is studied in three aspects: continuous rotation around the vertical axis,continuous rotation around the inclined axis and stepping rotation.The effects of different contact angles,liquid bridge volume,liquid viscosity and magnetic field intensity on the motion performance under various motion modes are studied.