Silicon nanowires (NWs) have attracted immense interest for sensing applications due to their high surface-to-volume ratio. In particular, field-effect-based chemical sensors are an attractive platform for fabricating multi-channel analysis systems capable of detecting bio-molecule concentrations and enzyme reactions. One can measure the concentrations of target analytes by taking advantage of changes in either capacitance or conductivity due to binding of chemical and biological species to the NW surface. However, most nanowire-based biochemical sensor studies employ planar field-effect transistor (FET) structures. In comparison, vertical freestanding FET structures sensors have a greater potential for ultrahigh sensitive detection because of the still larger exposed surface interaction area in high density arrays.<\/p>\n
One solution to fabricating vertically aligned FETs is through metal-catalyzed etching (MCE) [1<\/a>] <\/sup> [2<\/a>] <\/sup>, a low-cost, room temperature method which enables fabrication of highly ordered Si NW arrays of large aspect ratios (Figure 1). Such structures are very promising for the detection of multiple targets in an integrated microfluidic system. Improvement in sensor sensitivity using an electrolyte-semiconductor-silicon (EIS) sensor system was found to scale with nanowire length, translating into a stronger sensor signal when compared to a planar EIS sensor (Figure 2).<\/p>\n\n\t\t