SILICON TUBE STRUCTURES FOR A FLUID-DENSITY SENSOR

The influence on sensor performance of the dimensions of the first res onant silicon tube structure for measuring liquid fluid density is tes ted with regard to density sensitivity, vibration mode, resonance freq uency and Q-factor for four different double-loop designs. A new thin- walled structure with improved sensitivity is presented. The sensor co nsists of a tube system which oscillates in mechanical resonance. The structures are planar double-loop tubes of single-crystalline silicon fabricated using anisotropic silicon etching and silicon fusion bondin g, Tube structures with wall thicknesses of 100 and 50 mu m have been examined. They have fluid-density sensitivities of - 230 and - 320 ppm (kg m(-3))(-1), respectively.