CHEMFET (Chemically Sensitive Field-Effect Transistor) Chemical Warfare Agent Detector

摘要

In detector technology, one item whose feasibility as a cockpit chemical warfare agent detector has been demonstrated is the chemically sensitive field-effect transistor (CHEMFET). The overall objective of the present effort was: to test and evaluate CHEMFET semiconducting polymer gate electrode material; and to design, build and optimize a breadboard detector by using selected material. A membrane consisting of a poly (vinyl pyrrolidone), poly (vinyl alcohol), and copper (II) bipyridine mix (the selected material) was cast over copper/copper (bipyridyl) electrodes for form a cell, the resistance of which was shown to change on exposure to organophosphonates and other vapors. These resistance changes, however, originated at the metal-polymer contact and were not due to change in bulk resistivity. Since this membrane could not then be used as a gas-sensitive layer in a CHEMFET structure (as had originally been hoped), the direction of the research was changed. Because of the extreme sensitivity of impedance measurements, made as a function of diisopropyl methylphosphonate (DIMP) and other organophosphorous vapor concentrations, an effort has been planned and is progressing towards building a dedicated battery-operated low-frequency bridge to measure the impedance of the organophosphonate sensitive resistance cell.