title: Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis.
abstract: 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.
authors.affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan. yhtai@gate.sinica.edu.tw.
authors.forename: Yi-Hsin
authors.initials: YH
authors.lastname: Tai
authors.affiliation: Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan. b99b02014@gate.sinica.edu.tw.
authors.forename: Dao-Ming
authors.initials: DM
authors.lastname: Chang
authors.affiliation: Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 30013, Taiwan. mingyangpan@gmail.com.
authors.forename: Ming-Yang
authors.initials: MY
authors.lastname: Pan
authors.affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan. dwhuang@ntu.edu.tw.
authors.forename: Ding-Wei
authors.initials: DW
authors.lastname: Huang
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan. pkwei@sinica.edu.tw.|Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan. pkwei@sinica.edu.tw.
authors.forename: Pei-Kuen
authors.initials: PK
authors.lastname: Wei
keywords: E. coli; dielectrophoresis; refractive index; tapered fiber tip