D-dimer is a useful diagnostic biomarker for deep vein thrombosis or pulmonary embolism, collectively referred to as venous thromboembolism (VTE). The ability to detect in real-time the amount of D-dimer with a fast and reliable method is a key step to anticipate the appearance of these diseases. The combination of fiber-optic–based platforms for biosensing with the nanotechnologies is opening up the chance for the development of in situ, portable, lightweight, versatile, reliable and high-performance optical sensing devices towards lab-on-fiber technology. The generation of lossy mode resonances (LMRs) by means of the deposition of nm-thick absorbing metal-oxide films on special geometric-modified fibers allows measuring precisely and accurately surface refractive index changes, which are due to the binding interaction between a biological recognition element and the analyte under investigation. This approach enhances the light-matter interaction in a strong way, thus turning out to be more sensitive compared to other optical technology platforms, such as fiber gratings or surface plasmon resonance. Here, the results of a highly specific and sensitive biosensor for the detection of D-dimer based on LMR in fiber-optics are presented by monitoring in real-time the shift of the LMR related to the biomolecule interactions thanks to a conventional wavelength-interrogation system and an ad-hoc developed microfluidics. A detection limit of 100 ng/mL, a value 5-fold below the clinical cutoff value, has been attained for D-dimer spiked in human serum. The comparison of the results achieved with proteomics-based methodologies, which allows for the identification of betaand gamma-chains of fibrinogen, demonstrates the ability of our platform to specifically (<90%) recognize D-dimer.
The combination of fiber-optic–based platforms for biosensing with nanotechnologies is opening up the chance for the development of in situ, portable, lightweight, versatile, reliable and high-performance optical sensing devices. The route consists of the generation of lossy mode resonances (LMRs) by means of the deposition of nm-thick absorbing metaloxide films on special geometric-modified fibers. This allows measuring precisely and accurately the changes in surface refractive index due to the binding interaction between a biological recognition element and the analyte, with very high sensitivity compared to other optical technology platforms, such as fiber gratings or surface plasmon resonance. The proposed methodology, mixed with the use of specialty fiber structures such as D-shaped fibers, allows improving the light-matter interaction in a strong way. The shift of the LMR has been used to monitor in real-time the biomolecule interactions thanks to a conventional wavelength-interrogation system and an ad-hoc developed microfluidics. A big leap in performance has been attained by detecting femtomolar concentrations in real samples of human serum. The biosensor regeneration has been also studied by using a solution of sodium dodecyl sulphate (SDS), proving the device reusability. Therefore, this technology possibly represents a paradigm shift in the development of a simple, high-specificity and label-free biosensing platform, which can be applied to speed up diagnostic healthcare processes of different diseases toward an early diagnostic and personalized treatment system.
In this work, is presented the fabrication and characterization of optical fiber refractometer based on lossy mode resonances (LMR). Indium-Tin-Oxide (ITO) thin films deposited on optical fibers are used as the LMR supporting coatings. These resonances shift to the red as a function of the external refractive index. The refractometer has been used to characterize temperature variations related to the viscosity of synthetic industrial gear lubricant.
Three different optical fiber refractometers based on lossy mode resonances (LMRs) have been fabricated by means of the deposition of indium oxide thin-films. The sensitivity of the devices as well as the full-width at half maximum (FWHM) has been characterized as a function of the surrounding medium refractive index (from 1.332 to 1.471. Obtained results revealed that thinner coating possess higher sensitivities. However, the FWHM is better for thicker coatings. As a general rule, the thicker the In2O3 coating the lower the sensitivity, but the better the FWHM. Thus, a compromise is required depending on the necessities of the application.
This work introduces a new approach to characterize the multiphase flow by means of the utilization of optical fiber Bragg gratings. Here, the force applied by the air/liquid flow on the fiber gratings is the underlying mechanism of these sensors. Flow images are constructed from the response of a 8x8 mesh of sensors, with a total of 16 different FBGs multiplexed in wavelength. The data from each sensor has been processed in order to obtain a 2D plot of the air/liquid phase as well as a 3D plot of the air bubbles inside the tube for each time interval.
The fabrication and characterization of an optical fiber refractometer based on Lossy Mode Resonances (LMR) is presented. TiO2/ poly (sodium 4-styrenesulfonate) coatings deposited on side-polished D-shaped optical fibers are used as LMR supporting coatings. LMRs are sensitive to the external medium refractive index and D-shaped optical fibers enable the observation of TE and TM LMR polarizations. These refractometers based on TE and TM LMR showed an average sensitivity of 2737 nm/RIU and 2893 nm/RIU respectively for a surrounding medium refractive index (SMRI) range from 1.35 to 1.41.
In this work, the fabrication and characterization of novel humidity sensors based on Lossy Mode Resonances (LMR) is presented. Tin oxide (SnO2) coatings fabricated onto optical fibers are used as LMR supporting coatings. The SnO2 based refractometers showed an average sensitivity of 6715 nm/refractive index unit (RIU) in the range 1.333–1.420 RIU. The behavior of this optical fiber device as relative humidity (RH) sensor was also tested, monitoring its response to different surrounding humidity levels. The results show a sensitivity of 0.1 nm/RH% in the range from 20% to 80% RH.
In this work, the fabrication and characterization of refractometers based on lossy mode resonances (LMR) is presented.
Tin dioxide (SnO2) films deposited on optical fibers are used as the LMR supporting coatings. These resonances shift to
the red as a function of the external refractive index, enabling the fabrication of robust and highly reproducible
wavelength-based optical fiber refractometers. The obtained SnO2-based refractometer shows an average sensitivity of
7198 nm/refractive index unit (RIU) in the range 1.333-1.420 RIU.
In this work, it is described the fabrication and characterization of optical fiber refractometers based on lossy-mode
resonances (LMR) originated by deposition of different thin-film coatings around the optical fiber core. Two devices
with different coating materials are compared: one coated with conducting tin doped indium oxide (ITO) coatings and
the other one coated with semiconducting indium oxide. The response of these devices is characterized and compared as
a function of the external refractive index. The sensitivity obtained for indium oxide based refractometers resulted 39%
higher than that of ITO based ones when the resonance is located in the same spectral region. This behaviour is attributed
to the spectral characteristics of indium oxide, which allow an earlier generation of the resonance thanks to its higher
refractive index as well as permitting the accomplishment of LMR conditions in a wider spectral range. Moreover, these
devices are an adequate platform for the development of a wide variety of sensors by the addition of the suitable layer
onto the transparent oxide coating.
In this work, lossy mode resonance (LMR) based optical fiber refractometers are fabricated by using a transparent
coating (indium oxide), as the LMR supporting layer. The utilization of indium oxide coatings permits the fabrication of
highly sensitive optical fiber refractometers and enables the tunability of the LMR by adjusting the fabrication
parameters, such as the coating thickness. The detection technique is based on the wavelength shift of the LMR. In this
work it has been studied the influence of the external refractive index, achieving a maximum sensitivity of 2.24e-4
refractive index units per nanometer. Moreover, by adequated parameterization, more than one LMR can be observed in
the wavelength range analyzed in the experiments, which leads to a more accurate measurement of the refractive index.
Here, the fabrication and characterization of a novel optical fiber humidity sensor based on surface plasmon resonance
(SPR) in the infra-red region is presented. Firstly, an indium tin oxide (ITO) coating is deposited onto a 200 μm core
diameter optical fiber causing the shift of the SPR wavelength to the infra-red region. Then, the LbL method is used to
deposit a polymeric coating onto the ITO layer. The variations in the external humidity originated changes in the
thickness and refractive index of the polymeric coating and hence in the resonance.
In this work, surface plasmon resonance (SPR) based optical fiber sensors are proposed by using a transparent
conductive coating, Indium Tin Oxide (ITO) in our case, as the SPR supporting layer. The utilization of these ITO
coatings instead of using a thin film of gold or silver shifts the plasmon resonance band to the infra-red region and allows
the tunability of the SPR wavelength by adjusting the film fabrication parameters. The spectral response of these novel
devices is characterized, achieving a sensitivity of 0.00025 refractive index units per nanometer, which opens the door
for a wide range of applications.
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