Flow-velocity Microsensors Based on Semiconductor Fieldeffect Structures

A time-of-flight-type flow-velocity sensor employing the in-situ electrochemically generation of ion-tracers is developed. The sensor consists of an ion generator and two downstream-placed pH-sensitive Ta2O5-gate ISFETs (ion-sensitive field-effect transistor) that detect generated H+- or OH--ions. The results of the developed flow-velocity sensor under different modes of ion generation are presented and discussed. By applying this ISFET-array, the time of flight, and consequently, the flow velocity can be accurately evaluated using the shift of the response curve of the respective ISFETs in the array along the time scale. A good linearity between the measured flow velocity with the ISFET-array and the delivered flow rate of the pump is observed. In addition, a possibility of flowvelocity measurements by means of a LAPS (light-addressable potentiometric sensor) is firstly demonstrated.