TABLE OF CONTENTS The behavior of microelectrodes (radius smaller than 50 ?m) differs from conventionalsized electrodes (radius 1 mm or greater) in that nonlinear diffusion is the predominant mode of transport. This difference in mass transport from the bulk solution toward the electrode has several important implications that make microelectrodes very attractive in many areas of electroanalytical chemistry. These include reduced ohmic potential drop, a decreased time constant, a fast establishment of steady-state signals, and an increased signal-to-noise ratio.
Since the beginning of the 1980s (1, 2), the development of microfabrication techniques has allowed these electrodes to become widely used even though the benefits of the properties of small electrodes was recognized much earlier. Microelectrodes have thus been employed for those applications demanding electrochemistry in restricted volumes, in solutions of high resistance as well as in short-time regimes (1, 2). For a more detailed discussion about microelectrodes, see Chapter 6.
It was around the same time that the first reports on microelectrode arrays appeared. Both experimental and theoretical works (3 27) have demonstrated the advantages of such electrode assemblies, which result from the specific mass transport of electroactive materials or diffusion regimes taking place at their interface. These include the following:
As long as the microelectrodes in the array do not interact...
