Ultramicrodisc electrode

In a potentiostatic step experiment on an ultramicrodisc electrode, the current attains a limiting value in a time of the order r ID. In addition to this time scale becoming shorter with decreasing r, the mass transport rate of species to the electrode increases. As a consequence, one motivation for the development of devices using UMEs has been the resulting insensitivity of the limiting current to fluctuations of solution flow rate [62]. Hence UMEs have found widespread use as electrochemical detectors in fluid flow experiments, such as amperometric liquid chromatography (e.g., Ref. [63]) and flow injection analysis (e.g., Ref. [64]). Incidentally, this implies that the current should also be insensitive to vibration. 

In a recent development ultramicroelectrodes were used to obtain charge transfer diffusion cofficients for electroactive polymer films. Whiteley and Martin used chronoamperometry at Nation ionomer-coated electrodes to quantify the diffusional transport of ions in the polymer matrix. The experiment is simple in execution. The potential of the ionomer-coated ultramicrodisc electrode is stepped from a value where no redox activity occurs to one where the oxidation or reduction rate of the immobilized redox species is diffusion-controlled. Provided the diffusion layer within the film created by the potential step is always... 

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