In this chapter we explore the voltammetric responses that can be observed at regular and random arrays and how characterization via voltammetry may be sought. We also briefly consider the voltammetry at nanoparticle-modified electrodes and provide an overview of the various regular and random arrays that have been developed and utilized in electrochemical sensing, such as metallic, boron-doped diamond, screen-printed, and carbon nanotube arrays. 1.1 IntroductionThe pioneering work of Wightman and Fleishman on microelectrodes has undoubtedly significantly advanced the field of elec-trochemistry [1]. The International Union of Pure and Applied Chemistry (IUPAC) conventionally assumes that a microelectrode

has a dimension of tens of micrometers or less, down to the submi-crometer range [1]. Microelectrodes have the inherent advantage of a reduced ohmic drop, the rapid establishment of a steady-state sig-nal output, an increased signal-to-noise ratio, and a current increase due to enhanced mass transport [1-10]. While these improvements are highly beneficial and allow electrochemical reaction mecha-nisms and kinetics to be determined, trace electrochemical analysis to be achieved, and in vivo measurements to be applied, and also apply to highly resistive media, the very low current output is highly undesirable. This problem can be simply overcome through the ap-plication of a microelectrode array. Let us consider the voltammetry at an array of microelectrodes, as depicted in Fig. 1.1, where the dark circles in the scheme represent the microelectrodes that are at a fixed distance from their nearest neighbors in a cubic geometry [11].