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Sensors 2016, 16(3), 303;

Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis

Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan
Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 30013, Taiwan
Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: Galina Nemova
Received: 24 December 2015 / Revised: 19 February 2016 / Accepted: 23 February 2016 / Published: 27 February 2016
(This article belongs to the Special Issue SPR, WGM & Nano-Sensors: Advantages and Prospects)
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This work presents using a tapered fiber tip coated with thin metallic film to detect small particles in water with high sensitivity. When an AC voltage applied to the Ti/Al coated fiber tip and indium tin oxide (ITO) substrate, a gradient electric field at the fiber tip induced attractive/repulsive force to suspended small particles due to the frequency-dependent dielectrophoresis (DEP) effect. Such DEP force greatly enhanced the concentration of the small particles near the tip. The increase of the local concentration also increased the scattering of surface plasmon wave near the fiber tip. Combined both DEP effect and scattering optical near-field, we show the detection limit of the concentration for 1.36 μm polystyrene beads can be down to 1 particle/mL. The detection limit of the Escherichia coli (E. coli) bacteria was 20 CFU/mL. The fiber tip sensor takes advantages of ultrasmall volume, label-free and simple detection system. View Full-Text
Keywords: tapered fiber tip; refractive index; dielectrophoresis; E. coli tapered fiber tip; refractive index; dielectrophoresis; E. coli

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Tai, Y.-H.; Chang, D.-M.; Pan, M.-Y.; Huang, D.-W.; Wei, P.-K. Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis. Sensors 2016, 16, 303.

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