Silicon tube structures for a fluid-density sensor

The influence on sensor performance of the dimensions of the first resonant silicon tube structure for measuring liquid fluid density is tested with regard to density sensitivity, vibration mode, resonance frequency and Q-factor for four different double-loop designs. A new thin-walled structure with improved sensitivity is presented. The sensor consists 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 bonding, 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.