Comparative study of optical fiber immunosensors based on traditional antibody or nanobody for detecting HER2.

In this study, we present a novel biomarker detection platform employing a modified S-tapered fiber coated with gold nanoparticle/graphene oxide (GNP/GO) for quantifying human epidermal growth factor receptor-2 (HER2) concentrations, using antibodies as sensing elements. The fabrication of this device involves implementing an in-situ layer-by-layer technique coupled with a chemical adsorption step to achieve the self-assembly of GNP, GO, and antibodies on the STF surface. The detection mechanism relies on monitoring the refractive index changes induced by the adsorption of HER2 onto the immobilized antibodies. For comparative analysis, both monoclonal antibody (mAb) and the novel nanobody (Nb) were employed in constructing the STF immunosensor, referred to as the mAb immunosensor and Nb immunosensor, respectively. Spectral analysis results highlight that the Nb immunosensor exhibits twice the sensitivity of the mAb immunosensor. This enhanced sensitivity is attributed to the small size, high antigen affinity, strong specificity, and structural stability of Nb. The Nb immunosensor demonstrated an impressive detection limit of 0.001 nM for HER2, surpassing the detection limit of the mAb immunosensor. These findings underscore the potential of the proposed Nb immunosensor as a promising and sensitive tool for HER2 detection, contributing to the diagnosis and prognosis of breast cancer. Furthermore, the simplicity of production and excellent optical performance position the Nb immunosensor as a prospective real-time biosensor with minimal cytotoxicity.

Composite membrane of graphene oxide and gold nanoparticles functionalized S fiber taper aptasensor for highly sensitive bisphenol A detection.

The S fiber taper (SFT) aptasensor with a composite sensitive membrane of graphene oxide and gold nanoparticles was proposed for the rapid and highly sensitive detection of bisphenol A (BPA). The SFT was obtained using a fusion splicer; subsequently, the composite film was deposited on its surface, and the specific aptamer was covalently bonded to the surface of gold nanoparticles. The detection mechanism relies on monitoring changes in the external refractive index induced by the specific binding of BPA to the aptamer. The developed SFT aptasensor exhibited a remarkable sensitivity of 15.5 nm/nM and a limit of detection as low as 0.01 nM for BPA. These findings highlight the aptasensor's potential for diverse monitoring applications.

Over 50 W all-fiber mid-infrared supercontinuum laser.

Broadband supercontinuum laser sources in the mid-infrared region have attracted enormous interest and found significant applications in spectroscopy, imaging, sensing, defense, and security. Despite recent advances in mid-infrared supercontinuum laser sources using infrared fibers, the average power of those laser sources is limited to 10-watt-level, and further power scaling to over 50 W (or hundred-watt-level) remains a significant technological challenge. Here, we report an over 50 W all-fiber mid-infrared supercontinuum laser source with a spectral range from 1220 to 3740 nm, by using low loss (<0.1 dB/m) fluorotellurite fibers we developed as the nonlinear medium and a tilted fusion splicing method for reducing the reflection from the fluorotellurite-silica fiber joint. Furthermore, the scalability of all-fiber mid-infrared supercontinuum laser sources using fluorotellurite fibers is analyzed by considering thermal effects and optical damage, which verifies its potential of power scaling to hundred-watt-level. Our results pave the way for realizing all-fiber hundred-watt-level mid-infrared lasers for real applications.

High-sensitivity fiber optic temperature sensor based on CTFBG-FPI and Vernier effect.

A novel high-sensitivity temperature sensor based on a chirped thin-core fiber Bragg grating Fabry-Perot interferometer (CTFBG-FPI) and the Vernier effect is proposed and demonstrated. With femtosecond laser direct writing technology, two CTFBG-FPIs with different interferometric cavity lengths are inscribed inside a thin-core fiber to form a Vernier effect system. The two FPIs consist of two pairs of CTFBGs with a full width at half maximum (FWHM) of 66.5 nm staggered in parallel. The interferometric cavity lengths of the two FPIs were designed to be 2 mm and 1.98 mm as the reference arm and sensing arm of the sensor, respectively. The temperature sensitivity of this sensor was measured to be -1.084 nm/°C in a range of 40-90°C. This sensor is expected to play a crucial role in precision temperature measurement applications.

A 1-µm-Band Injection-Locked Semiconductor Laser with a High Side-Mode Suppression Ratio and Narrow Linewidth.

We demonstrate a narrow-linewidth, high side-mode suppression ratio (SMSR) semiconductor laser based on the external optical feedback injection locking technology of a femtosecond-apodized (Fs-apodized) fiber Bragg grating (FBG). A single frequency output is achieved by coupling and integrating a wide-gain quantum dot (QD) gain chip with a Fs-apodized FBG in a 1-µm band. We propose this low-cost and high-integration scheme for the preparation of a series of single-frequency seed sources in this wavelength range by characterizing the performance of 1030 nm and 1080 nm lasers. The lasers have a maximum SMSR of 66.3 dB and maximum output power of 134.6 mW. Additionally, the lasers have minimum Lorentzian linewidths that are measured to be 260.5 kHz; however, a minimum integral linewidth less than 180.4 kHz is observed by testing and analyzing the power spectra of the frequency noise values of the lasers.

Femtosecond laser inscribed helical sapphire fiber Bragg gratings.

This Letter reports a novel helical sapphire fiber Bragg grating (HSFBG) in a single crystal sapphire fiber with diameter of 60 µm fabricated by a 515 nm femtosecond laser. Due to the large refractive index modulation region and high structural symmetry of the HSFBGs, high-reflectivity and high-quality spectra can be prepared and additionally have good bending resistance. The spectral properties of HSFBGs with different helical diameters are studied. When the helical diameter is 30 µm, the reflectivity of HSFBG is 40%, the full width at half-maximum is 1.56 nm, and the signal-to-noise ratio is 16 dB. For the HSFBG bending test, the minimum bending radius is 5 mm, which can still maintain relatively good spectral quality. In addition, the HSFBG array with different periods has been successfully cascaded in a sapphire fiber. The experimental results of the HSFBG high-temperature test show that this HSFBG can work reliably at 1600°C, and the temperature sensitivity in the high-temperature range can reach 35.55 pm/°C. This HSFBG can be used in high-temperature and harsh environments, such as metal smelting and aeroengine structural health monitoring.

A Versatile Punch Stroke Correction Model for Trial V-Bending of Sheet Metals Based on Data-Driven Method.

During air bending of sheet metals, the correction of punch stroke for springback control is always implemented through repeated trial bending until achieving the forming accuracy of bending parts. In this study, a modelling method for correction of punch stroke is presented for guiding trial bending based on a data-driven technique. Firstly, the big data for the model are mainly generated from a large number of finite element simulations, considering many variables, e.g., material parameters, dimensions of V-dies and blanks, and processing parameters. Based on the big data, two punch stroke correction models are developed via neural network and dimensional analysis, respectively. The analytic comparison shows that the neural network model is more suitable for guiding trial bending of sheet metals than the dimensional analysis model, which has mechanical significance. The actual trial bending tests prove that the neural-network-based punch stroke correction model presents great versatility and accuracy in the guidance of trial bending, leading to a reduction in the number of trial bends and an improvement in the production efficiency of air bending.

Femtosecond laser inscribed chirped fiber Bragg gratings.

In this work, a method is proposed and demonstrated for fabrication of chirped fiber Bragg gratings (CFBGs) in single-mode fiber by femtosecond laser point-by-point inscription. CFBGs with bandwidths from 2 to 12 nm and dispersion ranges from 14.2 to 85 ps/nm are designed and achieved. The sensitivities of temperature and strain are 14.91 pm/°C and 1.21pm/µÎµ, respectively. Compared to the present phase mask method, femtosecond laser point-by-point inscription technology has the advantage of manufacturing CFBGs with different parameter flexibilities, and is expected to be widely applied in the future.

Light-Responsive Actuators Based on Graphene.

As a typical 2D carbon material, graphene, that possesses outstanding physical/chemical properties, has revealed great potential for developing soft actuators. Especially, the unique properties of graphene, including the excellent light absorption property, softness, and thermal conductivity, play very important roles in the development of light-responsive graphene actuators. At present, various light-driven actuators have been successfully developed based on graphene and its derivatives. In this mini review, we reviewed the recent advances in this field. The unique properties of graphene or graphene-related materials that are of benefit to the development of light-driven actuators have been summarized. Typical smart actuators based on different photothermal/photochemical effects, including photothermal expansion, photothermal desorption, photoisomerization, and photo-triggered shape memory effect, have been introduced. Besides, current challenges, and future perspective have been discussed. The rapid progress of light-responsive actuators based on graphene has greatly stimulated the development of graphene-based soft robotics.

Left atrial strain reproducibility using vendor-dependent and vendor-independent software.

BACKGROUND: Two-dimensional speckle-tracking echocardiography (2D-STE) enables objective assessment of left atrial (LA) deformation through the analysis of myocardial strain, which can be measured by different speckle-tracking software. The aim of this study was to compare the consistency of 3 different commercially available software, which include vendor-specific software for measuring left ventricle (VSSLV), vendor-independent software packages for measuring LV strain (VISLV) and vendor-independent software packages for measuring LA strain (VISLA). METHODS: Sixty-four subjects (mean age: 44 ± 16 years, 50% males) underwent conventional echocardiograms using a GE Vivid 9 (GE Ultrasound, Horten, Norway) cardiac ultrasound system. Standard apical 4 and 2 chamber views of the left atrium were obtained in each subject with a frame-rate range of 40-71 frames/s. LA strain during the contraction phase (Sct), conduit phase (Scd), reservoir phase (Sr = Sct + Scd) were analyzed by 2 independent observers and 3 different software. RESULTS: Sct, Scd, Sr were, respectively, - 11.26 ± 2.45%, - 16.77 ± 7.06%, and 28.03 ± 7.58% with VSSLV, - 14.77 ± 3.59%, - 23.17 ± 10.33%, and 38.23 ± 10.99% with VISLV, and - 14.80 ± 3.88%, - 23.94 ± 10.48%, and 38.73 ± 11.56% when VISLA was used. A comparison of strain measurements between VSSLV and VIS (VISLV and VISLA) showed VIS had significantly smaller mean differences and narrower limits of agreement. Similar results were observed in the coefficient of variation (CV) for measurements between VSSLV and VIS (VISLV and VISLA). Comparison of the intra-class correlation coefficients (ICCs) indicated that measurement reliability was weaker with VSSLV (ICC < 0.6) than with VIS (VISLV and VISLA) (ICC > 0.9). For intra-observer ICCs, VISLA > VSSLV = VISLV. For inter-observer ICCs, VSSLV > VISLA > VISLV. CONCLUSIONS: Software measurement results of LA strain vary considerably. We recommended not measuring LA strain across vendor platforms.

Compact fiber tip modal interferometer for high-temperature and transverse load measurements.

A compact fiber tip modal interferometer (FTMI) based on two-wave interference has been demonstrated. Its fabrication process is very simple, just involving fiber tapering by a fusion splicer. The effective sensing area of the FTMI has a small length of ~310 µm. The interference spectra of the fiber tips with different size and profile have been analyzed. The FTMI has a good mechanical strength and high-temperature stability. It can be used for high-temperature and transverse load sensing simultaneously in a harsh environment when two different attenuation peaks are chosen to be monitored.

Ultrasensitive temperature sensor based on an isopropanol-sealed optical microfiber taper.

We demonstrate an ultrasensitive temperature sensor based on an isopropanol-sealed optical microfiber taper (OMT) in a capillary. The OMT is highly sensitive to ambient refractive index (RI) with a maximum sensitivity of 18989 nm/RI unit in the range of 1.3955-1.4008. The thermo-optic effect of isopropanol and the thermal expansions of the sealant and sealed liquid turn the OMT into an ultrasensitive temperature sensor with the maximum sensitivity of -3.88 nm/°C in the range of 20°C-50°C. The temperature sensitivity contributions from different mechanisms are also investigated theoretically and experimentally.

Nanoporous TiO2/polyion thin-film-coated long-period grating sensors for the direct measurement of low-molecular-weight analytes.

We present novel nanoporous TiO(2)/polyion thin-film-coated long-period fiber grating (LPFG) sensors for the direct measurement of low-molecular-weight chemicals by monitoring the resonance wavelength shift. The hybrid overlay films are prepared by a simple layer-by-layer deposition approach, which is mainly based on the electrostatic interaction of TiO(2) nanoparticles and polyions. By the alternate immersion of LPFG into dispersions of TiO(2) nanoparticles and polyions, respectively, the so-formed TiO(2)/polyion thin film exhibits a unique nanoporous internal structure and has a relative higher refractive index than LPFG cladding. In particular, the porosity of the thin film reduces the diffusion coefficient and enhances the permeability retention of low-molecular-weight analytes within the porous film. The increases in the refractive index of the LPFG overlay results in a distinguished modulation of the resonance wavelength. Therefore, the detection sensitivity of LPFG sensors has been greatly improved, according to theoretical simulation. After the structure of the TiO(2)/polyion thin film was optimized, glucose solutions as an example with a low concentration of 10(-7) M was easily detected and monitored at room temperature.

Single S-tapered fiber Mach-Zehnder interferometers.

A fiber Mach-Zehnder interferometer (MZI) sensor, novel to our knowledge, based on a single "S"-like fiber taper has been fabricated via applying nonaxial pull in fiber tapering by a fusion splicer. The typical feature size of the structure has a length of 660 µm and the axial offset of 96 µm. This S fiber taper MZI has a refractive index (RI) sensitivity of 1590 nm/refractive index unit in the RI range of 1.409-1.425 and a strain sensitivity of about -60 pm/microstrain, which is 30 times higher than that of the normal two-taper-based MZI sensors.

Rapid fabrication of microhole array structured optical fibers.

A microhole array in a common single-mode fiber is fabricated by selective chemical etching of femtosecond-laser-induced fiber Bragg grating (FBG), which has a laser-modified region extending from the fiber core to the cladding-air boundary due to laser self-focusing. The shape and size of the orderly microhole on the fiber surface are controlled via changing conditions of FBG fabrication and chemical etching. A simultaneous sensing for surrounding refractive index and temperature is demonstrated by this microhole array FBG through measurement of the transmission power change and Bragg resonant wavelength shift.

Three dimensional hierarchy structures from self-assembly of quantum dots.

We have reported first example of 3D hierarchy structure from self-assembly of water-soluble QDs followed by chemical reaction control. After addition of ethylenediaminetetraacetic acid, dipotassium salt dehydrate (EDTA) into L-cysteine-stabilized CdTe QD solution, the color of solution was observed to become lighter and shallower, and finally white precipitates appeared. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirm that the morphology transformation from zero dimensional (0D) QDs via two-dimensional (2D) nanoflakes to 3D microflowers occurs among those QD assemblies. Meanwhile, EDX results demonstrate that the as-formed QD-assemblies are not CdTe but CdS. The turnover of chemistry nature from CdTe to CdS after addition of EDTA is mainly due to the oxidation of Te followed by a series of chemical reactions. The photoluminescence (PL) spectroscopy and confocal laser scanning microscopy (CLSM) results reveal that such 3D hierarchy structure of CdS QDs have good optical property.

Fabrication of a tilted fiber Bragg grating with a designed reflection spectrum profile.

A method of fabricating a tilted fiber Bragg grating (TFBG) with a designed reflection spectrum profile is proposed and demonstrated experimentally. In a reflective TFBG the central wavelength and the reflectivity are dependent on the tilt angles. Controlling the rate at which the tilt angle is continuously varied and the exposure dose in the UV-light writing process permits accurate control of the bandwidth and reflectivity of the grating. The experimental result agrees well with TFBG theory and calculation.