The Charge-Modulated Field-Effect Transistor (CMFET) is a device patented by the University of Cagliari, based on a floating gate transistor. The device is biased through a control capacitor, and a part of the floating gate (namely the sensing area) is exposed to the environment, thus making the CMFET a charge sensor. Indeed, any charge or charge distribution variation occurs in the near proximity of the sensing area is able to modulate the charge distribution inside the floating gate, thus affecting the charge carrier density inside the channel of the transistor. As a consequence, the threshold voltage of the transistor is modulated, finally determining a variation in the output current.
Interestingly, the CMFET working principle is independent on the technology chosen for the field-effect transistor fabrication. So far, CMOS and organic technology has been successfully employed to this aim; in the latter case, the device is named Organic CMFET (OCMFET).
The OCMFET has been originally conceived for biochemical applications, as it allows detecting those biochemical reactions related to charge/charge distribution variations, genetic, enzymatic, immunologic activity and pH variation. In the last years, it has been also successfully applied as cellular interface in vitro for electrically-active cells and as a sensor for physical variables, as pressure and temperature.