The ISFET pH electrode is a type of biosensor that measures ion concentrations in solution. When the ion concentration changes, the current through the transistor will change accordingly. This device has a significant impact on various fields, including chemistry, biology, and medicine.
What is an ISFET pH electrode?
An ISFET pH electrode is a field-effect transistor (FET) used for measuring ion concentrations in solution. The solution is used as the gate electrode, and a voltage between the substrate and oxide surfaces arises due to an ion sheath. This device is a special type of MOSFET (metal–oxide–semiconductor field-effect transistor) with the metal gate replaced by an ion-sensitive membrane, electrolyte solution, and reference electrode.
History
The ISFET was invented in 1970 and was the first biosensor FET (BioFET). This innovation marked a significant step forward in the development of biosensors, enabling the measurement of ion concentrations in solution.
Mechanism
The surface hydrolysis of Si–OH groups of the gate materials varies in aqueous solutions due to the pH value. Typical gate materials are SiO2, Si3N4, Al2O3, and Ta2O5. The mechanism responsible for the oxide surface charge can be described by the site binding model, which describes the equilibrium between the Si–OH surface sites and the H+ ions in the solution.
Key Facts
- The ISFET pH electrode measures ion concentrations in solution.
- The solution is used as the gate electrode.
- The voltage between the substrate and oxide surfaces arises due to an ion sheath.
- The ISFET is a special type of MOSFET with the metal gate replaced by an ion-sensitive membrane, electrolyte solution, and reference electrode.
- Typical gate materials are SiO2, Si3N4, Al2O3, and Ta2O5.
Applications
ISFET pH electrodes have a wide range of applications in various fields, including:
- Chemistry: For measuring pH levels in solutions.
- Biology: For measuring ion concentrations in biological samples.
- Medicine: For measuring pH levels in bodily fluids.
Examples
ISFET pH electrodes are used in various devices, including:
- pH meters
- Blood gas analyzers
- Urine analyzers
FAQ
What is the purpose of an ISFET pH electrode?
An ISFET pH electrode is used to measure ion concentrations in solution, allowing for the determination of pH levels.
How does an ISFET pH electrode work?
The ISFET pH electrode works by using the solution as the gate electrode, and a voltage between the substrate and oxide surfaces arises due to an ion sheath.
What are the advantages of an ISFET pH electrode?
The ISFET pH electrode has several advantages, including its ability to measure ion concentrations in solution, its high accuracy, and its ability to be miniaturized.
How long does an ISFET pH electrode typically last?
The lifespan of an ISFET pH electrode depends on the specific application and usage. Typically, they can last for several months or even years with proper maintenance.