To obtain the theoretical relationship between the resonant frequency of a rectangular micro-cantilever and the fluid density
the differential equation of the micro-cantilever coupled with fluid is established through the method of vacuum mode superposition instead of the fluid-structure interaction mode to obtain the fluid hydrodynamic pressure instead of the effect of fluid on the micro-cantilever. Then the equation is solved to acquire the function of the resonant frequency and fluid density by making use of the vacuum mode orthogonality. The resonant frequencies of silicon micro-cantilever chip immersed in the n-heptane and isooctane at 10-30 ℃ are calculated and compared with simulation values and experimental measurements. The absolute deviations of the calculation values of the resonant frequency from the simulation and experimental values get less than 2.8% and 0.9%
respectively. The theoretical formula can accurately describe the relationship between the resonant frequency of the rectangular micro-cantilever and the fluid density
which facilitates fluid density measurement and sensor miniaturization.
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references
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