A Microminiature Solid-State Capacitive Blood Pressure Transducer with Improved Sensitivity

A microminiature pressure transducer is described utilizing a variable air capacitor driven by a pressure-sensitive deflectible silicon membrane as the detection mechanism. Silicon integrated circuit technology is used throughout for economical batch fabrication of the device. Prototype devices have been fabricated and initial test results under static pressure conditions are reported. Equivalent gauge factors of over 500 for this variable capacitance device are about a factor of 5-10 better than the best theoretically designed silicon strain gauges in the size range necessary for catheter insertion. Temperature independence and increased linearity are also important advantages of this variable capacitance sensor head.