ISFET Based Microsensors for Environmental Monitoring

The use of microsensors for in-field monitoring of environmental parameters is gaining interest due to their advantages over conventional sensors. Among them microsensors based on semiconductor technology offer additional advantages such as small size, robustness, low output impedance and rapid response. Besides, the technology used allows integration of circuitry and multiple sensors in the same substrate and accordingly they can be implemented in compact probes for particular applications e.g., in situ monitoring and/or on-line measurements. In the field of microsensors for environmental applications, Ion Selective Field Effect Transistors (ISFETs) have a special interest. They are particularly helpful for measuring pH and other ions in small volumes and they can be integrated in compact flow cells for continuous measurements. In this paper the technologies used to fabricate ISFETs and a review of the role of ISFETs in the environmental field are presented

Field effect transistor with integrated microfluidic channel as pH sensor

International audienceThis paper presents an original design of chemical sensors with an integrated microfluidic channel. Targeted applications are pH-meters devices. The integration of the microfluidic channel allows decreasing the volume required for each measurement. The sensing part of the device consists of a field effect transistor (FET) with a suspended gate directly performed above the fluidic channel. Chemicals under test are driven through the sensing area between the electrical channel of the FET and the suspended gate. By this way products that flow in the microfluidic channel directly module the concentration of charges inside the transistor's gap and thus induce changes in the transfer characteristic. This paper describes the fabrication process and the technological choices for materials. Electrical tests, performed in air and in liquid, have shown a good behavior of the transistor, linked to a good mechanical sustain of the fluidic channel. The system is able to detect transition between air and liquid media. Moreover, it has shown a high sensitivity (about 300 mV/pH) to pH measurements