The microcantilever (MC) has become a common transducer for chemical and biological sensing in gas phase and liquid phase during recent years. MC sensors provide superior mass sensitivity by converting weak chemical and biological stimuli into high mechanical response. Moreover, other advantages such as small size, low cost and array format have made MCs more attractive than other comparable sensors. Selectivity in MC sensors can be enhanced by creating a differentially functionalized MC array (MCA) with responsive phases (RPs). A well-designed array should incorporate RPs exhibiting a variety of possible interactions with the analytes, and a specific analyte should induce a distinctive response pattern demonstrated by the array. The first major division of the dissertation research work focused on enhancing selectivity of MC sensor by creating a differentiating MCA. The MCs within the array were nanostructured in a previously developed manner. A self-designed capillary array was set up to chemically functionalize different ligands onto individual MCs in an array for metal ion sensing in liquid phase. Another array was prepared by selectively vapor depositing different organic RPs onto nanostructured MCs and applied to landfill siloxane sensing in gas phase. Both of the arrays demonstrated response diversity to the target analytes. The second major division of the dissertation research work focused on developing a new method to modify MC surfaces with a function nanostructure. Aluminium oxide nanoparticles (AONP) were uniformly dispersed onto MC and a roughened surface with high surface area was achieved as stable sensor platform. Alkoxysilyl compounds were then grafted onto this platform as RPs. For demonstration, a MCA functionalized with three different alkoxysilanes was prepared for volatile organic compound sensing in gas phase. Additionally, another MCA was functionalized with anti-human immunoglobulin G and anti-biotin for bio-sensing in liquid phase. Both of the arrays were prepared with the aforementioned capillary array setup. Selective responses of specific analytes, as well as good sensitivity, were obtained from each type of AONP MCA.