Self-regenerating photocatalytic sensor based on dielectrophoretically assembled TiO2 nanowires for chemical vapor sensing

Abstract In this paper we reported a new method to fabricate TiO 2 based chemical vapor sensor fabricated by dielectrophoretically assembling TiO 2 nanowires. Although TiO 2 based chemical sensors were previously reported, they were usually fabricated by the bottom-up methods, which involve tedious processes and cannot be scaled-up. In the current paper, we presented a top-down approach in the fabrication of TiO 2 nanowire based sensors. The TiO 2 nanowires were initially synthesized and subsequently directly assembled between two co-planar electrodes by dielectrophoresis in microfluidic devices. We used two different methods, ethylene glycol-mediated hydrolysis and high-voltage electrospinning, to synthesize TiO 2 nanowires with varied diameters and lengths. By incorporating a laminar flow field with AC electric fields, the control of the density of assembled TiO 2 nanowires was achieved adjusting AC frequencies and flow rates, which rendered this method repeatable and scalable for the fabrication of TiO 2 nanowire based devices. The sensing performances of chemical sensors based on the two kinds of TiO 2 nanowires were tested and compared. In the sensing experiments UV light was applied to activate the surface of TiO 2 nanowires, allowing them to be operated at room temperature. The results showed that the sensitivity of the self-regenerating chemical sensor based on TiO 2 nanowires synthesized by electrospinning exhibited 4.37 times higher than that of the nanowires prepared by the glycol-mediated hydrolysis method. The chemical sensor based on electrospun TiO 2 nanowires showed high sensitivity, fast response (less than 60 s) and fast recovery (less than 60 s) to vapor pollutants including NH 3 , acetone, and ethanol.