Abstract
This paper presents an improved TiO2 based vapor sensor fabricated by dielectrophoretically assembling TiO2 nanowires. Dielectrophoresis (DEP) offers the controllable, selective and massive manipulation of target nanowires. However, it is difficult to achieve precise assembly of nanowires based on dielectrophoresis. In this article we present a novel microelectrode design finger-type electrode to achieve precise assembly of nanowires based on dielectrophoresis. In this thesis, several important parameters including nanomaterial, solvent, AC frequency, flow rate, and the tip of electrode have been investigated systematically. In different nanomaterial or solution, the induced motion is determined by the dielectric properties and the conductivity of the nanomaterial and solution. And the number of nanowires will reduce with the increase of frequency and flow rate. In the finger-type electrodes, it could be to achieve precise assembly of nanowires based on dielectrophoresis by adjusting appropriately the DEP parameters. Furthermore, compared with the traditional electrode fabrication, electron-beam lithography, there are many the advantages of simple process, low cost, and convenience by using our novel hybrid electrode. According to experimental results, compared with the traditional nanowire nanosensors, our novel hybrid nanosensors after electrical sintering process exhibited higher sensitivity and lower limit of detection. The sensitivity of our novel hybrid nanosensors is 28.02% under 100 ppm concentration. The limit of detection is 1 ppm. The response time is 120 second. The S/N ratio is 14.432.With the aid of UV light, the sensor exhibits high sensitivity to vapor pollutants including NH3, acetone, and ethanol at room temperature. Our volatile organic compounds (VOCs) nanosensors is of increasing interest for a broad variety of applications in environmental safety monitoring and biomedical breath analysis.