An Introduction to mems (Micro-electromechanical Systems)

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Figure 34.  Schematic diagram of an MOSFET and ISFET [35]. 

ii) Biosensors 

Biosensors is the term used for a whole class of sensors that utilize a biochemical reaction to 

determine a specific compound.  A biosensor is generally a transducer combined with an 

immobilized enzyme or cell to monitor a specific change in the microenvironment.  Typically, 

an enzyme, antibody, polysaccharide or nucleic acid is used to interact with the substance to 

be measured.  The sensor itself can vary but a form of ISFET is typically used.  The probe tip 

is immersed in a liquid phase and is in contact with the process either directly or through a 

membrane.  They have not seen widespread use because as a class they exhibit many 

disadvantages including oxidization reactions with product, extreme sensitivity and the need 

for regular recalibration (not ideal for implantable devices). 

One of the most promising applications of an amperometric enzyme-based biosensor is the 

important for diabetes and also in the fermentation process.