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

Yi-Hsin Tai,Ding-Wei Huang,Pei-Kuen Wei,Dao-Ming Chang,Ming-Yang Pan

doi:10.3390/s16030303

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.

Highlights

Polluted drinking water could contain numerous of submicron/micron particles even though it looks crystal clear
The proposed Ti/Al coated optical fiber tip is sensitive to the environmental small particles
The electric field near the fiber tip results in a DEP force exerted on dielectric particles in the medium

Summary

Introduction

Polluted drinking water could contain numerous of submicron/micron particles even though it looks crystal clear. Some of these small particles, such as bacteria, could cause serious illnesses to the human body such as gastrointestinal infective disease, fever, or dehydration [1,2,3]. Optically label-free technologies are simple, real-time and cost-effective Some methods such as Bragg grating on periodic surface structure [6,7], surface plasmon resonance on gold surface have been demonstrated for the label-free detection of bacteria or DNA [8,9,10]. We present an ultrasensitive detection method for detecting small particles in water by using a tapered optical fiber tip coated with a thin metallic film. Combining it with a transparent electrode substrate, such as indium

Methods

Results

Conclusion