Zhenguo Jing

A Novel Fiber Optic Surface Plasmon Resonance Biosensors with Special Boronic Acid Derivative to Detect Glycoprotein

We proposed and demonstrated a novel tilted fiber Bragg grating (TFBG)-based surface plasmon resonance (SPR) label-free biosensor via a special boronic acid derivative to detect glycoprotein with high sensitivity and selectivity. TFBG, as an effective sensing element for optical sensing in near-infrared wavelengths, possess the unique capability of easily exciting the SPR effect on fiber surface which coated with a nano-scale metal layer. SPR properties can be accurately detected by measuring the variation of transmitted spectra at optical communication wavelengths. In our experiment, a 10° TFBG coated with a 50 nm gold film was manufactured to stimulate SPR on a sensor surface. To detect glycoprotein selectively, the sensor was immobilized using designed phenylboronic acid as the recognition molecule, which can covalently bond with 1,2- or 1,3-diols to form five- or six-membered cyclic complexes for attaching diol-containing biomolecules and proteins. The phenylboronic acid was synthetized with long alkyl groups offering more flexible space, which was able to improve the capability of binding glycoprotein. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with a protein concentration sensitivity up to 2.867 dB/ (mg/mL) and a limit of detection (LOD) of 15.56 nM.

Fiber-optic anemometer based on single-walled carbon nanotube coated tilted fiber Bragg grating

In this work, a novel and simple optical fiber hot-wire anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is proposed and demonstrated. For the hot-wire wind speed sensor design, TFBG is an ideal in-fiber sensing structure due to its unique features. It is utilized as both light coupling and temperature sensing element without using any geometry-modified or uncommon fiber, which simplifies the sensor structure. To further enhance the thermal conversion capability, SWCNTs are coated on the surface of the TFBG instead of traditional metallic materials, which have excellent thermal characteristics. When a laser light is pumped into the sensor, the pump light propagating in the core will be easily coupled into cladding of the fiber via the TFBG and strongly absorbed by the SWCNTs thin film. This absorption acts like a hot-wire raising the local temperature of the fiber, which is accurately detected by the TFBG resonance shift. In the experiments, the sensors performances were investigated and controlled by adjusting the inherent angle of the TFBG, the thickness of SWCNTs film, and the input power of the pump laser. It was demonstrated that the developed anemometer exhibited significant light absorption efficiency up to 93%, and the maximum temperature of the local area on the fiber was heated up to 146.1°C under the relatively low pump power of 97.76 mW. The sensitivity of -0.3667 nm/(m/s) at wind speed of 1.0 m/s was measured with the selected 12° TFBG and 1.6 μm film.

Theoretical study of high-sensitivity surface plasmon resonance fiber optic sensing technology

Surface Plasmon Resonance (SPR) has been widely investigated for chemical and biological sensing applications. Especially, fiber optic SPR sensors have recently drawn considerable attention because of their fundamentally simpler structure, lower cost, and suitability for remote-sensing applications. This paper will present a research work for a novel multichannel SPR sensing technology. Based on the Kretschmanns SPR theory, we theoretically investigate the surface parameters effects to SPR wavelength changes. Emphasis will be placed on a theoretical design and numerical simulation of a multichannel fiber optic SPR sensing scheme based on a geometrical tapered fiber optic sensor probe that coated with nanoparticles imprinted polymer on the SPR sensing region. The parameter effects of SPR sensing area that include metal thickness, sensing area length and dielectric overcoat layer. SPR spectra that change with incidence angle and wavelength are investigated by using numerical calculations and simulations. While nanoparticles imprinted polymer for enhancement of sensitivity can serve as an enhanced transduction mechanism for recognition and sensing of target analytes in accordance with different requirements, the scheme of a multichannel fiber optic SPR sensor can be further adapted to the design and development of multi-channel optical fibers SPR sensor probes by combining SPR with other technology as a comprehensive sensor design.

Boronic Acid Functionalized Au Nanoparticles for Selective MicroRNA Signal Amplification in Fiber-Optic Surface Plasmon Resonance Sensing System

MicroRNA (miRNA) regulates gene expression and plays a fundamental role in multiple biological processes. However, if both single-stranded RNA and DNA can bind with capture DNA on the sensing surface, selectively amplifying the complementary RNA signal is still challenging for researchers. Fiber-optic surface plasmon resonance (SPR) sensors are small, accurate, and convenient tools for monitoring biological interaction. In this paper, we present a high sensitivity microRNA detection technique using phenylboronic acid functionalized Au nanoparticles (PBA-AuNPs) in fiber-optic SPR sensing systems. Due to the inherent difficulty directly detecting the hybridized RNA on the sensing surface, the PBA-AuNPs were used to selectively amplify the signal of target miRNA. The result shows that the method has high selectivity and sensitivity for miRNA, with a detection limit at 2.7 × 10-13 M (0.27 pM). This PBA-AuNPs amplification strategy is universally applicable for RNA detection with various sensing technologies, such as surface-enhanced Raman spectroscopy and electrochemistry, among others.

Detection of glycoprotein using fiber optic surface plasmon resonance sensors with boronic acid

In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) labelfree sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/(mg/ml) and the limit of detection was 2∗10−5g/ml.

Non-contact Micro Vibration Measurement System Based on Non-equilibrium Optical Fiber Michelson Interferometer

In this paper, a non-equilibrium optical fiber Michelson interferometer is used to realize non-contact micro vibration measurement. The frequency response range of 10~300Hz and the displacement resolution of 2nm in vibration are realized.

Non-contact Micro Vibration Measurement System Based on Optical Fiber Michelson Interferometer

In this paper, an optical fiber Michelson interferometer is used to realize non-contact micro vibration measurement. The frequency response range of 1~1KHz and the displacement resolution of 1nm in vibration measurement are implemented.

Temperature compensation fiber-optic refractive index sensor based on single-mode fiber core-offset attenuator

This paper has developed a novel single-mode core-offset fiber optic sensor based on the principle of Michelson interferometer, which can be used for refractive index measurement in sugar solution while making temperature compensation to eliminate or weaken temperature sensitivity. Experimental results show that when the temperature range is from 18.1°C to 84.3°C there will be an increasing relationship between characteristic wavelength and temperature. When the sensors sensing range is from 1.331 to 1.335, there will be a better decrease gradually relationship between characteristic wavelength and refractive index (0.0416nm/0.01R.I.U) after temperature compensation. This sensor has a simple-structure and high-sensitivity.

Fiber Bragg Grating dynamic demodulation based on non-equilibrium interferometry

Non-equilibrium interferometric Fiber Bragg Grating (FBG) sensor is suitable for the accurate measurements of high-frequency dynamic stress, vibration, etc because of its high sensitivity and high frequency response compared to other types of FBG sensors. In this paper, a Phase Generation Carrier (PGC) demodulation technique of non-equilibrium interferometric FBG sensor that based on ARCTAN algorithm by using an arctangent algorithm with a simple method, has been investigated, which can avoid the high-frequency noise increases, the error accumulation, the integrator signal jump of the integrator and other inherent weaknesses in the system. ARCTAN has a better response characteristic of the mutant signals, especially for low-frequency large-signal that can be demodulated with a greater range. The experimental result demonstrate that implementing measured resolution can up to 10nε/√Hz@500Hz in vibration strain, a signal sampling rate to 100 KHz and a frequency response range up to 1 KHz. This method can improve the performance of the system greatly which has potential significance for practical sensor application.

Cladding-mode obtained by core-offset structure and applied in Fiber Bragg Grating sensor

Comparing to core-modes of optical fibers, some cladding-modes are more sensitive to the surroundings which are very valuable to sensing application; recently, a novel type of FBG sensor with core-offset structure attracts more and more interests. Normally, the forward core-mode is not only reflected and coupled to the backward core mode by the Fiber Bragg Grating in the step-type photosensitive single mode fiber, but also coupled to the backward cladding-modes and the radiation modes, eventually they will leak or be absorbed by the high refraction index coating layer. These backward cladding-modes can also be used for sensing analysis. In this paper, we propose and develop a core-offset structure to obtain the backward core-mode and backward cladding-modes by using the wavelength shift of the backward core-mode and the power of the backward cladding-modes in Fiber Bragg Grating sensor, and the power of the backward cladding-modes are independent from temperature variation. We develop a mode coupling sensor model between the forward core-mode and the backward cladding-modes, and demonstrate two coupling methods in the core-offset structure experimentally. The sensor is fabricated and demonstrated for refractive index monitoring. Some specific works are under investigation now, more analysis and fabrication will be done to improve this cladding-mode based sensor design for applicable sensing technology.