• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.723-727
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• 2008

Sensing performances of evanescent field absorption (EFA) hetero-core fiber sensor has been presented based on EFA by changing the length and the core diameter of the single mode fiber. Experimental results have demonstrated a good feature in their relationship between the length and the core diameter of the single mode fiber. The sensor consists of 2 fiber optics which have the same cladding diameter of $125{\mu}m$ However one fiber optic used is single mode and has varying core diameter ranging from 3.3 to $5.6{\mu}m$. The other fiber is multimode type and has a thicker fixed core diameter of $62.5{\mu}m$. The 2 fiber optics are thermally spliced together. Experiments conducted to measure the resonance wavelength were carried out over a range of refractive index, to find the optimum sensing length Experiments show that core diameter of the single mode fiber and sensing length offects the linearity and sensitivity.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.50-56
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• 1994

Fiber-optic biosensor for the detection of organophosphorus compounds in a contaminated water was developed, which was the component of pesticides and agricultural agent. The detection principle of designed sensor was the pH variance induced by a reaction of acetylcholinesterase enzyme inhibited by organophosphorus compounds. The pH variance was detected by the optical system to measure the organophosphorus compounds. Litmus was selected as the pH-sensitive dye suitable to the enzyme reaction and a light source to be detected by the optical system. The enzyme entrapped in Ca-alginate gel was immobilized at the inner wall to maintain the high activity of enzyme and to be reused for a long period. The optical fiber was used to miniaturize and control remotely the sensor system. The He-Ne laser with 632 nm was selected as the light source to prevent light intensity fluctuation by the product. Cheap plastic optical fibers were used as the transmission part of the light and the phototransistor was used as the reception part of light based on the wavelength of He-Ne laser. The proposed fiber-optic biosensor has the linear analytical range of 0 ppm-1.5 ppm with response time of 5 minutes.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.369-374
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• 2008

A novel fiber optic surface plasmon resonance (SPR) sensor using cyclic olefin copolymer (COC) prism with the spectral modulation is presented. The SPR sensor chip is fabricated using the SU-8 photolithography, Ni-electroplating and COC injection molding process. The sidewall of the COC prism is partially deposited with Au/Cr (45/2.nm thickness) by e-beam evaporator, and the thermal bonding process is conducted for micro fluidic channels and optical fibers alignment. The SPR spectrum for a phosphate buffered saline (0.1.M PBS, pH.7.2) solution shows a distinctive dip at 1300.nm wavelength, which shifts toward longer wavelength with respect to the bovine serum albumin (BSA)concentrations. The sensitivity of the wavelength shift is $1.16\;nm{\cdot}{\mu}g^{-1}{\cdot}{\mu}l^{-1}$. From the wavelength of SPR dips, the refractive indices (RI) of the BSA solutions can be theoretically calculated using Kretchmann configuration, and the change rate of the RI was found to be $2.3{\times}10^{-5}RI{\cdot}{\mu}g^{-1}{\cdot}l^{-1}$. The realized fiber optic SPR sensor with a COC prism has clearly shown the feasibility of a new disposable, low cost and miniaturized SPR biosensor for biochemical molecular analyses.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.16-23
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• 1994

Developed fiber-optic biosensor for the detection of organophosphorus compounds in a contaminated water needs the analysis of an enzyme kinetics and the transport phenomena in the reaction part to analyze the sensor signal and to design the sensor. The enzyme inhibition kinetics was investigated and the reactor model was proposed to design the reaction part in the proposed sensor. Since the acetylcholinesterase was inhibited by the organophosphorus compounds, experiments for enzyme inhibition reaction were performed from 0 to 2 ppm to be detected by the developed sensor, and irreversible enzyme inhibition kinetics was proposed. The reactor parts were divided into the two phases, i.e. bulk phase and immobilized enzyme layer, to analyze the flow and diffusion. Sensor signal was able to be analyzed based on the total reactor model established by linking the enzyme reaction kinetics. Based on the proposed model, the effects of loading enzyme amount and enzyme layer thickness on the magnitude of readout signal were simulated.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.401-401
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• 2014

In this study, graphene, the most attractive material today, has been applied to the wavelength-modulated surface plasmon resonance (SPR) sensor. The optical fiber sensor technology is the most fascinating topic because of its several benefits. In addition to this, the SPR phenomenon enables the detection of biomaterials to be label-free, highly sensitive, and accurate. Therefore, the optical fiber SPR sensor has powerful advantages to detect biomaterials. Meanwhile, Graphene shows superior mechanical, electrical, and optical characteristics, so that it has tremendous potential to be applied to any applications. Especially, grapheme has tighter confinement plasmon and relatively long propagation distances, so that it can enhance the light-matter interactions (F. H. L. Koppens, et al., Nano Lett., 2011). Accordingly, we coated graphene on the optical fiber probe which we fabricated to compose the wavelength-modulated SPR sensor (Figure 1.). The graphene film was synthesized via thermal chemical vapor deposition (CVD) process. Synthesized graphene was transferred on the core exposed region of fiber optic by lift-off method. Detected analytes were biotinylated double cross-over DNA structure (DXB) and Streptavidin (SA) as the ligand-receptor binding model. The preliminary results showed the SPR signal shifts for the DXB and SA binding rather than the concentration change.

• KSBB Journal
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• v.10 no.1
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• pp.105-112
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• 1995

The fiber-optic biosensor using enzyme-immobilized Langmuir-Blodgett film is developed fort the measurement of ethanol. The enzyme, alcohol dehydrogenase, is immobilized at the molecular level on the arachidic acid monolayer using Langmuir-Blodgett film technique. Based on the ordered multisubstrate mechanism, the immobilized enzyme kinetics is investigated. The optical sensing system is proposed, and sensor signal is proportional to ethanol concentration and is related wish the number of enzyme layers. As the number of deposited LB film layer increases up to 20 1ayers, the high ethanol concentration of 45mM can be measured without the saturation of signal. Surface pressure-area isotherm is measured for the three-different charged-lipids. Arachidic acid is the most suitable for the adsorption of alcohol dehydrogenase based on electrostatic force.