Sensor systems for multi-parameter detection in fluidics usually combine different sensors, which are designed to detect only one physical or (bio-)chemical parameter. In the present work, an ISFET (ion-sensitive field-effect transistor), which is well known as a (bio-)chemical sensor, is utilised for the flow velocity and flow direction measurement for the first time. The proposed flow sensor presents a chemical sensor-actuator system and consists of a H+-ion generator and a pH ISFET that detects the in-situ electrochemically generated H+ ions. By measuring the time of flight, the flow velocity can be determined. Since this measuring method represents a dynamic method, a calibration of the sensor usually is not required, because only relative changes in the sensor output signal are of interest. Moreover, sensor+s drift, temperature instability and sensitivity discrepancy between the various ISFETs are not relevant. The experimental results show good linearity between the measured flow velocity with the ISFET and the delivered flow rate of the pump. Due to the fast response of the ISFET (usually in the millisecond range), an ISFET-based flow sensor is suitable for the measurement of the flow velocity in a wide range. The results of the flow direction measurement with two ISFETs are presented, too.

Date Published: 28 September 2001
PDF: 9 pages
Proc. SPIE 4560, Microfluidics and BioMEMS, (28 September 2001); doi: 10.1117/12.443050

Published in SPIE Proceedings Vol. 4560:
Microfluidics and BioMEMS
Carlos H. Mastrangelo; Holger Becker, Editor(s)