Sensitive Continuous Monitoring of pH thanks to Matrix of several Suspended Gate Field Effect Transistors

摘要

An SGFET-type charge sensor matrix has been processed by standard microelectronics technology and bonded on a PCB card in order to realise a full electronic pH-meter. The detection principle is based on the field effect mechanism of MOSFET. Detections have been performed thanks two different electrical methods. Both have given interesting results. Sampling methods have proved its reversibility and its effectiveness for pH monitoring. Sensitivity of 13μA/pH have been found, which could fit with several applications especially the water quality monitoring. The sweep measurement method which is more complex to adjust has given sensitivity of 400mV/pH in the same domain of pH, this result shows particularly the high level of sensitivity induced by the SGFET technologies. Electric measures reliability have been improved by optimising the way of test, limiting the sampling time and averaging the drain current value on this small period. Next experiments will try to increase the reliability of the measure by development of specific cleaning and rinse protocols. Furthermore we are going to develop a microcontroller device to monitor more sharply the measure protocol with the SGFET matrix. In fact one of the main advantages of an electronic pH-meter is the possibility to integrate near the sensor in the silicon chip electronic functions for the signal treatment and the data storage.