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Figure 12. /D versus time for poly(P-V-H2+)-based microelectrochemical transistor upon variation of pH, Va = -0.5 V versus SCE, VD = 200 mV.and microelectrodes 1, 3, 5, and 7 are regarded as the "drain" of the transistor. The device is on at pH 3 for V0 = -0.5 V versus SCE and VO = 200 mV. Upon changing the pH of the solution from pH 3 to 5, the device is turned from on to off. Because the reduction potential of the protonated monoquaternized bipyridinium is pH dependent, the increase in pH causes a change in the redox potential. At pH 5, the E0' of this polymer is -0.67 V versus SCE. All the redox sites of poly(P-V-H2+) are in the oxidized form when VG = -0.5 V versus SCE and charge transfer is blocked. There is no current flow between source and drain. These results are consistent with the expectations of redox conduction and the pH-dependent electrochemical behavior of poly(P-V-H2+). ConclusionsThe poly(P-V-Me2+)-based transistor allows the demonstration of the characteristics of a microelectrochemical transistor based on a conventional redox polymer as the "channel". The conventional redox polymer endows the device with a unique ID-VG characteristic: a narrow range of VG (~200 mV), where /D > 0 with a sharp, pH-independent /D peak at VG = E°' of the redox

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