The Technology
Ion sensitive field effect transistors (ISFET), are used to detect presence and concentrations of various species of ions in fluids into which they are placed. ISFETs have long been considered good candidates for providing small, fast, sensitive, accurate, and relatively inexpensive chemical and biochemical sensors. An ISFET typically comprises a reference electrode and a metal- oxide-semiconductor field effect transistor (MOSFET) modified to accumulate target ions the ISFET is intended to detect. In operation, ISFETs have too often proven to be relatively unstable and labile sensors that exhibit long and short term drifts in sensitivity and require calibration at frequencies that limit their utility. In addition, for many applications it has been difficult to satisfactorily protect ISFETs from damage by components of fluids in which they are used. The current solution are also not applicable to small scale sensors.
The technology enables accomplishment of acidity (pH) measurements, or ions concentration measurements in general, using monolithic silicon ISFETs, with a small, simple, inaccurate and unstable reference electrode (pseudo reference electrode) which can be implemented monolithically on the same chip with the ISFETs.
Advantages
- Simplifies the fabrication process of ISFET devices and reduces its cost, by separating the sensing electrodes from the MOS circuitry.
- Eliminates the need for individual calibration of every ISFET device
- Significantly reduces the drift and instability of the output signal over time
Applications and Opportunities
- Any application of acidity (pH) measurement, or ions concentration measurement
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