| Compared with traditional sensors,micro-nano sensor has the advantages of small size,light weight,low power consumption,good durability,low price,stable performance and high quality,minimal mass,high resonance frequency and quality factor(Q value).As the ultra-sensitive sensor,it has been widely used in the field of science and technology.In order to obtain accurate resonance frequency measurement results,it is needed to be measured in vacuum.However,micro-nano sensor often need to work in the fluid or gas environment in many cases.When the sensor is immersed in the fluid(liquid or gas)environment,the vibration of the sensor is affected by damping,and the energy dissipation increases.Therefore,the resonance frequency is greatly reduced,and the accuracy of the measurement results is also affected.It is very important to predict the influence of damping on the micro-nano resonator in the fluid environment for the design and application of micro-nano sensors.In this paper,the dynamic characteristics of a planar two-dimensional suspended film with a fixed edge in fluid environment are studied,and the theory,simulation and experimental test of the resonant film are carried out.According to the theory of film vibration,the expression of natural frequency in vacuum is obtained;Applying the Rayleigh equation method,the fluid solid coupling dynamic equation of the thin film under the fixed boundary condition are deduced;The fluid structure coupling analysis of the circular film and the square film is carried out by using ANSYS simulation software,and the resonance frequencies and modes of each order in the fluid are obtained.Subsequently,the vibration characteristics of circular film and square film are compared and analyzed;In order to investigate the effect of residual stress,the vibration equation of thin film with residual stress in vacuum is acquired;Considering the effects of residual stress and fluid damping,the fluid solid coupling dynamic model of thin film is established.Then the influence of the thin film with residual stress in the fluid was simulated by ANSYS.Circular film and square film with different sizes are made of 304 stainless steel flake,and the package and fixed clamped support are carried out.Applying the experimental platform,the natural frequencies of each order of the film are tested.Then in order to explore the effect of residual stress on the film on air damping,SiC films with a thickness of about 1083nm and 1000?m to 2500?m in diameter are also tested.The vibration frequency of the film is tested with the change of air damping under different external pressure.Finally,the experiment is verified by theory and simulation.The results show that when the air damping is taken into account,the resonance frequency of thin film is decreasing.The size of air damping depends on the environmental pressure ratio.The increase of this ratio means the influence of air damping on the dynamic behavior of micro-film is greater.The study also shows that the influence of air damping on the fundamental order vibration mode is greater than that of high order mode at the same time as the number of nodal circles. |
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