pH sensing from frequency response of SGFET

PH measurements, in particular the detection of its small changes is important for environment as in water monitoring, and for many chemical or biological applications. These applications require the development of microsystems that present high sensitivity to pH changes, are able to make continuous measurements, and have a simple use, a low cost and a small size. This work describes the microsystems which present these specifications. Their architecture consists in pH sensors integrated with microfluidic system, allowing continuous transport and testing of the fluid. The pH sensors are suspended gate transistors which showed high sensitivity, and the microfluidic channels associated to these sensors are made in PDMS technology. The compatibility of the two technologies has been developed and allows a good sticking, a continuous flow, and a good electrical insulation. The pH variations can be checked with high sensitivity by detecting current or gate voltage changes.