A method of positioning a catalyst nanoparticle that facilitates nanowire growth for nanowire-based device fabrication employs a structure having a vertical sidewall formed on a substrate. The methods include forming the structure, forming a targeted region in a surface of either the structure or the substrate, and forming a catalyst nanoparticle in the targeted region using one of a variety of techniques. The techniques control the position of the catalyst nanoparticle for subsequent nanowire growth. A resonant sensor system includes a nanowire-based resonant sensor and means for accessing the nanowire. The sensor includes an electrode and a nanowire resonator. The electrode is electrically isolated from the substrate. One or more of the substrate is electrically conductive, the nanowire resonator is electrically conductive, and the sensor further comprises another electrode. The nanowire resonator responds to an environmental change by displaying a change in oscillatory behavior.