U-bent Fiber Research Articles

Plastic Optical Fiber as Water-Level Sensor

This research presents a low-cost sensor for measuring liquid levels using plastic optical fibers (POF). The sensor reduces the scattering-based optical losses in the fiber, which increase linearly with the liquid height. A U-bent fiber probe and photodetector are used to detect the change in optical intensity. The U-bent probe serves as a test probe for measuring the liquid level. The voltage response difference of the photodetector provides liquid level measurement. This study demonstrates the sensor's responsiveness to liquid level fluctuations above 55 cm at varying temperatures. Sensitivity levels of 1.4 and 3.3 mV/mm were achieved for water level fluctuations below and above 45 cm, respectively. Furthermore, the sensor demonstrated consistently stable responsiveness over multiple cycles.

Evanescent-Field Excited Surface Plasmon-Enhanced U-Bent Fiber Probes Coated with Au and ZnO Nanoparticles for Humidity Detection

We report the design, fabrication, and testing of a humidity sensor based on an optical fiber-based evanescent wave probe. The fiber was bent into a U-shape and de-cladded at the location of the bending. The de-cladded section was coated either with Au or with ZnO nanoparticles. Humidity is detected based on the interaction in the surface plasmon resonance of the Au/ZnO nanoparticles excited by an evanescent wave of light passing through the optical fiber. The response of the U-bent fibers to humidity was investigated using a specifically designed low-voltage portable interrogation box. We found that the fibers coated with ZnO nanoparticles were able to detect a minimum 0.1% change in humidity with an average sensitivity of 143 µV/%RH and 95% linearity over the 10% to 80% humidity range. In comparison, samples coated with Au and Au + ZnO nanoparticles demonstrated a minimum change detection of 0.3% RH and 2% RH respectively. The response and recovery time of the sensor were measured to be 3 s and 4 s, respectively, for a 60% change in humidity from 20% to 80%. The entire measurement system was operated by consuming an electrical power of 1.62 W at an input voltage of 12 Vdc.

Anti-nucleolin aptamer mediated specific detection of cancer cells by Localized Surface Plasmon Resonance-based U-bent optical fiber

The detection of Circulating Tumor Cells (CTCs) is of profound importance for cancer diagnosis and monitoring in diseased patients. In the presented work, an aptasensor for CTC detection was developed using AS1411 aptamer specific for nucleolin on cancer cells’ surface as receptor on Gold NanoParticles (GNPs) decorated U-bent optical fiber. The aptamer binds to target upon folding into a parallel G-quadruplex structure, and therefore, components of folding and running buffer were optimized to 50 mM tris buffer and 100 mM KCl with and without 5 mM Mg+2 based on Circular Dichroism spectroscopy (CD) and bright field microscopy respectively. Further, the binding of aptamer and MCF-7 cells to GNP coated U-bent fiber were validated by fluorescence microscopy. The aptasensor showed significantly higher absorbance for 104 cancer cells (retinoblastoma, meningioma, breast, cervical, and colon cancer cells) as compared to non-cancer cells (MCF-10A and WBCs) with a t-test p-value of 0.0012. On an optical bench, aptasensor was able to detect as low as 500 cells/mL. To develop a portable and small CTC detection system, aptasensor was integrated with a hand-held opto-electronic device μSens (custom developed in our lab) and was able to detect 50 cells/mL. This is the first time a portable sensing system based on U-bent optical fiber was tested for sensing cancer cells. The ability to detect diverse types of cancer cells by AS1411 aptamer is promising and paves the way for the detection of circulating tumor cells in blood samples, with relative ease and low cost.

Metal-Organic Framework-Based Fiber Optic Sensor for Chromium(VI) Detection.

This study demonstrates a novel fiber optic sensing strategy for selective adsorption and rapid detection of Cr(VI) ions by exploiting a suitable metal-organic framework matrix and the characteristic spectral absorption of Cr(VI) at 395 nm wavelength, respectively. U-bent fiber optic sensor (U-FOS) probes that exhibit remarkably high evanescent wave-based absorbance sensitivity were employed to efficiently detect the Cr(VI) ions that are adsorbed to a stable zeolitic imidazolate framework (ZIF-67) matrix immobilized on the probe surface. A facile technique was developed for the fabrication of ZIF-67-coated U-FOS probes (FOS/ZIF-67) involving an in situ deposition process followed by heat treatment. Selectivity of the FOS/ZIF-67 probes to Cr(VI) was confirmed by optical absorption spectral investigations with 14 other heavy metals and interfering ions. The sensor performance was evaluated with a compact light-emitting diode-photodetector-based setup. FOS/ZIF-67 probes demonstrate an ability to detect Cr(VI) ions with a limit of detection of 1 ppb and a wide linear dynamic range from 0.005 to 100 ppm within a short response time of 5 to 10 min. These sensors show good recovery rates with real water samples and a shelf-life of at least 4 weeks under ambient conditions, thereby demonstrating their viability for real-world application.

A U-bent fiberoptic absorbance biosensor array (ArFAB) for multiplexed analyte detection

Compact and dip-type U-bent fiber optic sensor (U-FOS) probes exhibit remarkably high evanescent wave absorbance (EWA) sensitivity and are highly suitable for label-free multiplexed detection of proteins, virii and bacteria by exploiting their intrinsic optical absorption property in the UV region. Here, we show the design and development of a novel EWA based eight-channel array fiber optic absorbance biosensor (ArFAB) using U-FOS probes for multi-analyte detection or multi-sample analysis in real-time. A proof-of-concept ArFAB is designed to consist of a UV LED (λmax = 285 nm) and a highly sensitive CMOS linear image sensor coupled to a sensor probe module through fan-out (1-to-8) and parallel (8 nos) fiber bundles respectively. The sensor probe module is designed to hold and efficiently couple the light to/from 8 U-FOS probes with the help of ceramic ferrules and mating sleeves. The CMOS line sensor, with 8 coupling fibers equidistantly placed along its length, distinctly quantifies the intensity response from each of the eight U-FOS probes. The ArFAB was systematically validated for reproducible optical intensity measurements and label-free multiplexed detection of proteins and bacteria was realized. Moreover, a novel sandwich immunoassay with plasmonic labels for immunoglobulin G (IgG) with picomolar analyte detection limits at 280 nm wavelength is demonstrated. With mass-producible U-FOS probes and a low-cost optoelectronic instrumentation that can be easily customized for LSPR or any other sensing phenomenon, the ArFAB is highly promising for cost-effective biomolecular interactions, and cell analyses and clinical diagnostic applications.

Detection of tomato leaf curl New Delhi virus DNA using U-bent optical fiber-based LSPR probes

The detection of Tomato leaf curl New Delhi virus (ToLCNDV) DNA has been presented using U-bent fiber optic sensor (FOS) by an evanescent wave absorption method in the visible region. The localized surface plasmon resonance (LSPR) based FOS was developed by immobilizing gold nanoparticles on the amine-functionalized surface and the receptor probe was prepared by attaching a short segment of the complementary DNA (cDNA) on this surface. Further, the cDNA attachment was confirmed by monitoring the real-time change in LSPR absorption spectra. The conjugation protocol of single-strand DNA (ssDNA) from the viral genome of ToLCNDV was established like antibody-antigen-based assays by observing the real-time change in absorption kinetics. Consequently, a linear correlation between ssDNA concentration and the conjugation-dependent change in refractive index (RI) has been observed. The limit of detection (LOD) using two different cDNA immobilized FOS probes was determined to be 50±10 ng/μL and the change in RI was found 12.5±1.3×10−4 RIU/Abs. From this systematic binding study, a straightforward target-specific sensor has been constructed using a digital electronic logic gate analogy. This device has significant commercial potential for the development of a portable LSPR sensor for real-time detection of plant pathogens in addition to the possibility of multi-target environments.

U-Bent Plastic Optical Fiber Sensor for Iron in Iron Supplements

In this paper, we have designed a U-bent fiber optic sensor based on evanescent wave absorption for iron detection and quantification in the iron tablet. A detailed investigation of the impact of the bend-induced material deformation on the refractive index losses, numerical aperture, light propagation inside core and absorption coefficient has been presented. The experiment results of the developed sensor demonstrate the sensor sensitivity as 0.0316 O. D/ppm with a linear regression coefficient (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of 98.1%.

Step-etched U-bent silica fiber optic probes – Design and optimum geometry for refractive index sensing

This study presents a ray-optics based model for the multimode U-bent silica fiber optic refractive index (RI) sensor probes, followed by a detailed experimental investigation to identify the optimum fiber core (d) and bend diameter (D), and the optimal bend ratio (D/d). U-bent probes with different geometries (d = 200, 400 and 600 µm; D = 1.0, 1.5, 2.0, and 2.5 mm) were fabricated and evaluated for their RI sensitivity in terms of refractive losses. Among the bend ratios between 1.7 and 12.5, the U-bent probes with a bend ratio between 3 and 5 exhibit a higher RI sensitivity for a given core diameter. Among the twelve different geometries tested, U-bent probes with 600 µm core and ~2.5 mm bend diameter demonstrate the highest RI sensitivity of ~6 ∆A/RIU, measured as a change in absorbance (∆A) per refractive index unit (RIU). Further investigations to improve light-medium interactions by wet chemical step-etching of the silica fiber core show a gradual improvement in the RI sensitivity until a etched waist diameter of 200 µm, followed by an abrupt drop. At least a two-fold improvement in the RI sensitivity was observed. A compact LED-photodetector based dip-type handheld refractometer was realized as a proof-of-the-concept to demonstrate the feasibility of using these etched probes in reusable or disposable form for RI based analytical applications.

Fabrication of Humidity-Resistant Optical Fiber Sensor for Ammonia Sensing Using Diazo Resin-Photocrosslinked Films with a Porphyrin-Polystyrene Binary Mixture.

Ammonia gas sensors were fabricated via layer-by-layer (LbL) deposition of diazo resin (DAR) and a binary mixture of tetrakis(4-sulfophenyl)porphine (TSPP) and poly(styrene sulfonate) (PSS) onto the core of a multimode U-bent optical fiber. The penetration of light transferred into the evanescent field was enhanced by stripping the polymer cladding and coating the fiber core. The electrostatic interaction between the diazonium ion in DAR and the sulfonate residues in TSPP and PSS was converted into covalent bonds using UV irradiation. The photoreaction between the layers was confirmed by UV-vis and Fourier transform infrared spectroscopy. The sensitivity of the optical fiber sensors to ammonia was linear when exposed to ammonia gases generated from aqueous ammonia solutions at a concentration of approximately 17 parts per million (ppm). This linearity extended up to 50 ppm when the exposure time (30 s) was shortened. The response and recovery times were reduced to 30 s with a 5-cycle DAR/TSPP+PSS (as a mixture of 1 mM TSPP and 0.025 wt% PSS in water) film sensor. The limit of detection (LOD) of the optimized sensor was estimated to be 0.31 ppm for ammonia in solution, corresponding to approximately 0.03 ppm of ammonia gas. It is hypothesized that the presence of the hydrophobic moiety of PSS in the matrix suppressed the effects of humidity on the sensor response. The sensor response was stable and reproducible over seven days. The PSS-containing U-bent fiber sensor also showed superior sensitivity to ammonia when examined alongside amine and non-amine analytes.

Plasmonic Fiberoptic Absorbance Biosensor (P-FAB) for Rapid Detection of SARS-CoV-2 Nucleocapsid Protein.

SARS-CoV-2 nucleocapsid protein-based COVID-19 diagnosis is a promising alternative to the high-priced, time-consuming, and labor-intensive RT-PCR tests. Here, we developed a rapid, dip-type, wash-free plasmonic fiber optic absorbance biosensor (P-FAB) strategy for the point-of-care detection of SARS-CoV-2 N-protein, expressed abundantly during the infection. P-FAB involves a sandwich assay with plasmonic labels on the surface of a U-bent fiber optic sensor probe with a high evanescent wave absorbance (EWA) sensitivity. The SARS-CoV-2 N-protein is quantified in terms of the change in the intensity of the light propagating through the U-bent sensor probe coupled to a green LED and a photodetector. Firstly, the optical fiber material (silica vs. polymeric optical fiber), was evaluated to realize a sensitive sensor platform. The optimal size of AuNP labels (20, 40, and 60 nm) to achieve high sensitivity and a lower limit of detection (LoD) was investigated. Following the P-FAB strategy, fused silica/glass optical fiber (GOF) U-bent senor probe and citrate-capped AuNP labels (size ~40 nm) gave rise to an LoD down to ~2.5 ng/mL within 10 mins of read-out time. Further, studies on development and validation of a point of care (PoC) read-out device, and preclinical studies are in progress.

Highly Stable Plasmonic Nanostructures on a Nickel-Sputtered Glass and Polymeric Optical Fiber Sensors

This study shows development of highly sensitive and stable localized surface plasmon resonance (LSPR)-active U-bent glass and polymeric optical fiber (GOF and POF) sensor probes by a seed-mediated in situ growth technique. Here, the nickel/nickel oxide seeds (Ni/NiO, 3 to 5 nm size) were formed on the U-region of the fiber probe by sputter coating nickel under a low vacuum (3 Pa), and then, gold nanostructures (AuNSs) were grown over the Ni/NiO seeds. The evanescent wave absorbance (EWA) phenomenon in the U-bent fiber probe was exploited to monitor the growth kinetics of AuNSs in real-time. Experimental observations point to a potential galvanic replacement of Ni by Au. The newly formed AuNSs on U-bent GOF and POF probes gave rise to a LSPR-based refractive index sensitivity of 27.66 and 25.65 ΔA/ΔRIU with plasmonic peak at 600 and 570 nm, respectively. These plasmonic probes show an excellent chemical and mechanical stability, in addition to high surface enhanced Raman scattering (SERS) activity. This quick and facile technique is highly suitable for large-scale manufacture of reliable plasmonic fiber optic sensor probes for chemical and bio sensing applications.

Vector magnetic field sensor based on U-bent single-mode fiber and magnetic fluid.

A novel, compact, and easy fabrication vector magnetic field sensor has been proposed and investigated. The proposed sensor consists of a U-bent single-mode fiber fixed in a magnetic-fluid-filled vessel. Neither mechanical modification nor additional fiber grating is needed during the sensor fabrication. The results show that the response of magnetic fluid to magnetic field can be used to measure the direction and intensity of magnetic field via whispering gallery modes supported by the U-bent fiber structure with suitable bending radius. The sensitivity of direction is 0.251 nm/°, and the maximum magnetic field intensity sensitivity is 0.517 nm/mT. Besides, the results of this work prove the feasibility for realizing vector magnetic sensors based on other bending structures (such as bending multimode interference, bending SPR structure) in the future.

A plasmonic fiberoptic absorbance biosensor for mannose-capped lipoarabinomannan based tuberculosis diagnosis

Tuberculosis (TB) is a resurgent infectious disease affecting a large number of people in the developing countries. An on-site, affordable diagnostic screening at an early-stage for an immediate anti-TB treatment is known to tremendously minimize the high mortality rates. Lipoarabinomannan (LAM), a surface glycolipid, has been identified as a potential TB biomarker present in urine at ultra-low concentrations of a few fg/mL. Here, we report a plasmonic fiber optic absorbance biosensor (P-FAB) strategy for mannosylated LAM (Man-LAM or Mtb LAM) detection down to attomolar concentrations. It involves a plasmonic sandwich immunoassay on a U-bent fiber optic probe with gold plasmonic (AuNP) labels functionalized with anti-Mtb LAM immunoglobulin M (IgM) and anti-Mtb LAM IgG respectively. The Mtb LAM is quantified in terms of absorption of light passing through the fiber probe using a green LED and a photodetector. The choice of fiber optic probes (fused silica versus polymer), the optimum size (20, 40, 60 and 80 nm) and concentration (2 × , 10 × , and 20 × ) of AuNP labels were investigated to obtain high sensitivity and lower limits of analyte detection (LoD). P-FAB with a simple LED-photodetector pair, 200 μm fused silica U-bent fiber probe and 60 nm (20 × ) AuNP labels gave LoDs down to 1 fg/mL and 10 fg/mL in the buffer and synthetic urine respectively. Moreover, the anti-Mtb LAM IgM bound sensor probes and the AuNP reagent stored at 4 °C were stable up to 45 days. P-FAB based Mtb LAM sensor demonstrates its potential for an on-site TB diagnosis.

U-bent fiber optic plasmonic biosensor platform for ultrasensitive analyte detection

This study demonstrates a rapid, wash-free, dip-type plasmonic fiberoptic absorbance biosensor (P-FAB) capable of zeptomole analyte detection and 6-orders of wide dynamic range. It involves a sandwich immunoassay on a compact U-bent fiber optic probe surface that works by dipping an antibody-functionalized probe into a mixture of sample and gold nanoparticle (AuNP) label suspension. The U-bent fiberoptic probes with a high evanescent wave absorbance sensitivity allow detection of the high extinction AuNP labels measured in terms of light intensity change using a pair of LED and photodetector (PD). This simple and low-cost P-FAB gives an unprecedented detection limit of 0.17 zeptomole for human immunoglobulin G (HIgG) in 25 μL buffer in just 25 min. Further silver enhancement of AuNP labels for 5 min results in a limit of quantitation (LoQ) down to 0.17 zeptomole (∼100−150 molecules in 25 μL), making P-FAB a highly sensitive and low-cost technology for point-of-care diagnostics.

Controlled In Situ Seed-Mediated Growth of Gold and Silver Nanoparticles on an Optical Fiber Platform for Plasmonic Sensing Applications

This study presents an in situ growth technique to develop highly sensitive plasmonic fiber optic sensors with an excellent control over the plasmonic properties of gold (AuNPs) and silver nanoparticles (AgNPs). Here, we exploit the dual functionality of the U-bent fiber optic sensor (FOS) probes, where the probe acts as, firstly, the substrate for nanoparticles’ growth and, secondly, an invaluable tool to monitor as well as control the gold and silver seed binding to the surface amine groups and subsequently their growth in real time by means of the evanescent wave absorbance (EWA) spectral response. Au and Ag seeds (< 5 nm) with a peak absorbance at 510 and 390 nm, respectively, were used. The NP growth kinetics from the probes for different seed densities with a peak EWA response of 0.05, 0.1, and 0.15 optical density (OD) were observed in the presence of the respective metal precursor, cetyltrimethylammonium bromide (CTAB), and ascorbic acid. In comparison with AuNP grown FOS, a significant anisotropic growth was observed for AgNP with a redshift and spectral width as high as 215 nm and 425 nm, respectively, for a peak EWA response of 2.0 OD. The localized surface plasmon resonance (LSPR) activity of the AuNPs and AgNP grown FOS probes was evaluated for seed density of 0.1 OD. These proof-of-the-concept studies show significantly high RI sensitivity and surface-enhanced Raman scattering (SERS) enhancement factor for AgNP probes at 15.8 ΔA/RIU (for 22 AgNPs/μm2) and 1.3 × 107, respectively, in comparison with 18.9 ΔA/RIU (for 1424 AuNPs/μm2) and 1.1 × 106, respectively, for AuNP FOS probes. In addition, these plasmonic probes were stable in organic solvent (hexane) but its stability was deteriorated in alkaline solution (1 M NaOH).

Triangular silver nanoparticle U-bent fiber sensor based on localized surface plasmon resonance

Optical sensors with local surface plasmon resonance (LSPR) of noble metal (gold, silver, platinum) nanoparticles have received extensive attention due to their excellent detection performance. Here, we propose an LSPR fiber-optic sensor with a graphene oxide/triangular silver nanoparticle structure. Benefiting from the LSPR characteristics of the silver triangle nanoparticles, the use of triangular silver nanoparticles provides significant sensitivity enhancement. In order to highlight the enhancement of silver triangle nanoparticles, we chose the commonly used silver spherical nanoparticles as a comparison. We used the finite difference time domain method to model and calculate the local electric field and extinction efficiency for the two shapes of silver nanoparticles. The simulation results show that the local electric field intensity of triangular silver nanoparticles is 10 times that of spherical silver nanoparticles, and the extinction efficiency is 4 times that of spherical silver nanoparticles. In the experiment, a U-shaped LSPR fiber sensor with spherical and triangular silver nanoparticles was fabricated. The former has a refractive index sensitivity of 342.7 nm/RIU and the latter has a sensitivity of 1116.8 nm/RIU. Even if there is temperature interference during the detection process, the detection result will not produce a large error.

Plastic fiber optic sensor for continuous liquid level monitoring

The study demonstrates the development of a novel low-cost plastic optical fiber (POF) based sensor for liquid level measurement. The sensor works on the principle of reduction in scattering-based optical losses (in contrast to the increase in optical losses for evanescent wave-based sensing) in a straight decladded fiber with an increase in the liquid level due to refractive index changes in the medium surrounding the fiber. A compact optical setup is developed in-house consisting of two U-bent fiber probes coupled to a single LED on one end and two photodetectors on the other ends to measure the optical intensity changes. One of the U-bent probes is decladded over the length of the fiber to act as a test probe to measure the liquid level, while the other probe acts as a reference to compensate for the light intensity fluctuations due to light source instability and ambient conditions. The difference in voltage responses of the two photodetectors gives a measure for liquid level. We have investigated the fiber optic level sensor response to rising and falling liquid levels over 55 cm in presence of aqueous liquids of different refractive index values (1.33 to 1.38) and 95% ethanol as well as DI water at various temperatures from 16 °C up to 70 °C. A level sensitivity of 1.4 and 3.3 mV/mm for water level changes was obtained for the liquid level below and above 45 cm respectively. In addition, the fiber optic level sensor shows a stable and reproducible response over several cycles of 30 min duration at different liquid levels. The results demonstrate that this fiber optic level sensor is not only easy-to-make, cost-effective and robust but also offers sensitive, stable and reproducible instantaneous level measurements.

Plasmonic biosensors for bacterial endotoxin detection on biomimetic C-18 supported fiber optic probes

Bacterial endotoxins such as lipopolysaccharides (LPS) are major contaminants of most pharmaceutical and consumer products. We report an antibiotic-mediated plasmonic biosensor for LPS detection based on a facile U-bent fiber optic probe (UFOP) technology. Biomimetic self-assembled layer of octadecyltrichlorosilanes (OTS) were functionalized on the surface of optical fiber probes to hydrophobically entrap LPS from aqueous solutions. The binding of LPS molecules was monitored in real-time by measuring the change in refractive index (RI) in the evanescent layer. To add specificity and signal amplification, the bound LPS molecules were further tagged with antimicrobial polymyxin-B conjugated gold nanoparticles (PMB-AuNPs) in a sandwich format. The assay was extensively optimized by investigating the role of experimental parameters like OTS concentration, incubation time and addition of a silver reduction step at the end of the assay. The lower limit of detection (LOD) for LPS was found to be 0.4 ng/mL with a 36-fold improved sensitivity upon silver enhancement. The total assay time was 1 h. The assay was also found to be highly specific in the presence of common biopharmaceutical components and could thus serve as an efficient endotoxin detection platform for quality control testing during therapeutic development.

In-situ growth of AuNPs on WS2@U-bent optical fiber for evanescent wave absorption sensor

The sensitivity of the evanescent wave absorption sensor is always a hot topic which has been attracted researchers' discussion. It is still a challenge for developing the effective sensor to sensitively detect some biochemical molecules solution in a simple and low-cost way. In this paper, an evanescent wave absorption (EWA) sensor has been presented based on the U-bent multimode fiber coated with tungsten disulfide (WS2) film and in-situ growth of gold nanoparticles (AuNPs) for the detection of ethanol solution and sodium chloride (NaCl) solution. Benefitted from the effective light coupling produced between U-bent probe and AuNPs, we attained the optimal size of the AuNPs by changing the reaction time between WS2 and tetrachloroauric acid (HAuCl4). With the AuNPs/WS2@U-bent optical fiber, we discussed the behaviors of EWA sensor, such as sensitivity, reproducibility, fast response-recovery time and stability. The sensitivity (△A/△C) of the proposed AuNPs/WS2@U-bent optical fiber EWA sensor is 0.65 for the detection of the ethanol solution. Besides, the AuNPs/WS2@U-bent optical fiber EWA sensor exhibits high sensitivity in detection of the sodium chloride (NaCl), which can reach 1.5 when the proposed sensor was immersed into NaCl solution. Our work demonstrates that the U-bent optical fiber EWA sensor may have promising applications in testing the solution of concentration.

Evanescent wave absorption sensor with direct-growth MoS2 film based on U-bent tapered multimode fiber

In this work, we presented a novel evanescent wave absorption sensor based on U-bent tapered multimode fiber covered by molybdenum disulfide (MoS2) film (MoS2@TU fiber EWA sensor). The multimode fiber was manufactured by the fused tapered fiber machine, and then heated using a butane candle flame and bent into a U-bent structure. MoS2 was grown on the fiber directly by thermally decomposing the precursor of (NH4)2MoS4. We have demonstrated that the MoS2 can be applied in the filed of EWA sensor, and the EWA sensor based on U-bent tapered multimode fiber (TU fiber) possessed higher sensitivity than that based on U-bent fiber. The sensitivity (ΔA/ΔC) of the developed EWA sensor is 0.34 in detection of ethanol solution. It shows good sensitivity, linearity, repeatability and stability in detection. And the developed EWA sensor also shows good performance in detection of the adenosine solution, this work shows that the developed EWA sensor may have promising applications in biosensing.