A versatile method to grow localized arrays of nanowires for highly sensitive capacitive devices

We propose a new approach to increase the detection efficiency of the capacitive sensing devices, by growing vertically aligned nanowires arrays, localized and confined on small interdigited electrodes structures. The metallic tracks are made using optical lithography, and the nanowires are realized by electrochemical synthesis in nanoporous materials (i.e. supported alumina templates). By controlling the preparation conditions, both their positions and pitches can be easily tuned, as well as their geometrical design (i.e. diameters between 5 - 350 nm and lengths between 150 nm - 10 mu m). Based on these considerations, a capacitive sensor structure with high active surface is sensitized with polyaniline, for pH detection. Reported data show that the sensitivity of the sensor is substantially improved by using nanowires arrays.