An invasive catheter flow sensor with on-chip CMOS read-out electronics for the online determination of blood flow

A silicon flow sensor with integrated electronics for invasive blood flow measurement has been developed and investigated. The flow sensor is based on a silicon-on-insulator SIMOX substrate (Separation by Implated Oxygen) with a backside etched silicon membrane containing oxide trenches and uses a differential thermal measurement principle. The chosen fabrication process is fully CMOS-compatible. An on-chip switched capacitor circuitry converts the flow signal into a pulse width modulated signal. The device has been tested in a blood circulation simulator in the flow range of 0-10 l/min.