Microelectrochemical transistor electrolytes

Not long ago,this group first described microelectrochemical devices, which are based on microfabricated arrays of electrodes, connected by electroactive materials. Because the active components of these devices are chemical in nature, many of these devices are chemically sensitive,and comprise a potentially useful class of chemical sensors. Devices showing sensitivity to pH, 02r 2 f and Na" have been demonstrated. These devices are, typically, operated in fluid solution electrolytes. If this class of devices is to be useful as gas sensors, systems which are not dependent on liquid electrolytes need to be developed. We have recently reported solid state microelectrochemical transistors, which replace conventional liquid electrolytes with polymer electrolytes based on polyethyleneoxide (PEG) and polyvinylalcohol (PVA). In this report, we discuss additional progress toward solid-state devices by employing a new polymer ion conductor based on the polyphosphazene comb-polymer, MEEP (shown below). By taking advantage of polymer ion conductors we have developed microelectrochemical devices, where all of the components of the device are confined to a chip. 

Figure 5 shows an example from a new class of solid-state microelectrochemical transistors, which are based on redox-active molecules dissolved in the polymer. The redox-active material is N,N,N, N -tetramethyl-p-phenylenediamine (TMPD) which is sublimed into the MEEP/LiCF3S03 film. Here, the MEEP/LiCF3S03 acts as both polymer host and electrolyte. The transistor characteristic of this device is also shown in Figure 5. Below 0.0 V vs. Ag, the device is off, Iq = 0, since all the TMPD is neutral. As TMPD is oxidized, the device turns on, with a maximum Iq near /2 TMPD" /. We have...

SOLID-STATE MICROELECTROCHEMICAL DEVICES TRANSISTOR AND DIODE DEVICES EMPLOYING A SOLID POLYMER ELECTROLYTE... 

WO3 is an example of another class of electroactive material, metal oxides, which has been used to construct microelectrochemical devices. WO3 is a wide-band-gap semiconductor, with high resistance in its neutral state.Upon reduction, WO3 intercalates cations such as H" ", Li" ", and Na and becomes conducting. W03 based transistors, showing sensitivity to pH and to Li" concentration have been demonstrated in solution electrolytes. A schematic of a MEEP/WO3 device is shown in Figure 3. WO3 is confined to the required electrodes, using standard photolithographic techniques. 

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See also in sourсe #XX -- [ , , , ]

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