Ion Sensitive Organic Field-Effect Transistors ISOFETs

1 Ion Sensitive Organic Field-Effect Transistors (ISOFETs) 

Ion Sensitive Field-Effect Transistors (ISFETs) developed to measure pH and to sense a variety of analytes in solution are well known in the silicon technology field [11]. In these devices the gate insulator is in direct contact with the electrolyte solution (see Fig. 6.1). 

To investigate the pH response, the device was immersed in the buffer solution together with the reference electrode and was biased as a typical FET in a common source configuration. The authors explain the working mechanism by coupling the site-binding theory developed for electrolyte/dielectric 

The reference electrode and the microfluidic channel are directly assembled on top of the gate insulating layer. As a result, the polymer FET reported in this work can be integrated with disposable lab-on-a-chip platforms, which is very attractive for in vivo applications. Also in this case the application of the device can be extended to the detection of biomolecules by modifying the gate layer with a proper functionalization membrane. 

We have proposed still another approach [9] A 900-nm thick Mylar foil is used as H+-sensitive layer and also as mechanical support of the whole device. The main feature of the proposed device is that it is a mechanical support-free, lightweight and totally flexible structure (see Fig. 6.4). 

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Fig. 6.2. Cross section of an ion sensitive organic field-effect transistor (ISOFET) [14], Copyright 2001 IEEE...

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