Eccentric Core Research Articles

High-sensitivity lossy mode resonance sensor by deposition of perovskite nanofilms on the eccentric core quasi D-shaped photonic quasi-crystal fiber

High-sensitivity lossy mode resonance sensor by deposition of perovskite nanofilms on the eccentric core quasi D-shaped photonic quasi-crystal fiber

Eccentric Core Photonic Crystal Fiber Magnetic Field Sensor Based on Surface Plasmon Resonance with Extremely High Linearity

Eccentric Core Photonic Crystal Fiber Magnetic Field Sensor Based on Surface Plasmon Resonance with Extremely High Linearity

Large Range Curvature Measurement Using FBGs in Two-Core Fiber with Protective Coating

In this work, we propose a fiber Bragg grating (FBG)-based sensor for curvature measurements. Two gratings are inscribed through the protective coating in a specialty optical fiber using focused femtosecond laser pulses and point-by-point direct writing technology. One grating is inscribed on the central core adjacent to an air channel, while the other is inscribed on the eccentric core. The bending characteristics of the two-core fiber strongly depend on the bending direction due to the asymmetry of the fiber cores. A bending sensitivity of 58 pm/m−1 is achieved by the FBG in the eccentric fiber core over the curvature range of 0–50 m−1 . Temperature and humidity cross-sensitivity could be significantly reduced by analyzing the differences in peak shifts between the two gratings. The sensor features a large sensing range and good robustness due to the presence of its protective buffer coating, which makes it a good candidate for curvature sensing in engineering fields.

Photonic hook propagation from eccentric microcylinder

The Photonic hook (PH) is an intricately curved photonic nanojet (PNJ) or a highly intense electromagnetic beam featuring a subwavelength waist, whose principal hallmark lies in its capacity to bend light at the nanoscale. According to existing literature, the origin of PH can be attributed to symmetry breaking, whereas symmetrical microstructures predominantly contribute to PNJ formation. This study presents the novel revelation of PH emergence from an isolated eccentric core–shell dielectric microcylinder, achieved through the illumination of a paraxial Gaussian beam (PGB). The eccentrically structured core–shell microscale geometry introduces an additional degree of freedom, influencing PH formation and directly shaping its characteristic parameters. Much like PNJ, the propagation of PH depends on different parameters such as core and shell refractive indices of the micro-structures, microstructure geometry, incident light type, and direction of propagation. A fascinating outcome from our numerical simulations is the switchable occurrence of PNJ and PH from an eccentric core–shell microcylinder by a simple adjustment of eccentricity, either parallel or perpendicular to the PGB’s propagation direction. This computational investigation emphasizes the impact of eccentricity and the incident wave’s beam waist, maintaining a consistent refractive index contrast between the core and shell. The outcomes are interpreted in terms of key parameters governing PH generation characteristics, encompassing FWHM, maximum electric field enhancement, and focal plane. Notably, we have observed the coexistence of whispering gallery modes (WGM) and PH within this system and these modes exhibit high sensitivity to the excitation wavelength. The potential applications of PH are believed to be far-reaching, including areas like optical trapping, sensing, and functioning as a versatile focusing element. This study contributes to the fundamental understanding of PH and illuminates its potential as a robust tool across diverse optical applications.

Effects of different strength and velocity training programs on physical performance in youth futsal players

Futsal is a high intensity team sport with intermittent actions of short duration, so it is necessary to include different training strategies to improve explosive actions. There is a gap in the scientific literature regarding training programs that improve the performance of young futsal players. The aim of this study was to determine the effects of different strength and velocity training programs on lower body physical performance in youth futsal players. Forty-two youth futsal players were divided into control group (CG, n = 14) and a strength intervention group (SG, n = 14), which included a weekly session for 8 weeks of eccentric strength training, plyometrics and core strengthening, and a velocity intervention group (VG, n = 14), which included a weekly session during 8 weeks of training with linear speed exercises and with change of direction, accelerations with resistance bands and core strengthening. SG significantly improved horizontal jump (HJ) (p:0.02), V-CUT (p:0.91) and change of direction deficit (CODD) (p:0.01). VG showed significant improvements in HJ (p:0.01), in 25 m sprint (p:0.01), in total repeated sprint ability time (p:0.01), in V-CUT (p:0.01) and in CODD (p:0.01). SG showed significant intergroup differences (p:0.01) in COD variables with respect to CG and VG. In conclusion, SG and VG showed significant improvements in lower body performance variables in youth futsal players. In addition, the SG has substantial changes in COD compared to the other two groups, so it has a greater effect.

Dual transverse fiber tip Fabry-Perot cavities for simultaneous measurements of pressure and temperature

A fiber tip sensor based on dual transverse Fabry-Perot (FP) cavities for simultaneous temperature and gas pressure measurements is proposed, fabricated and tested. The proposed fiber tip sensor is formed by one-step polishing the end face of a microstructure fiber, which contains a hollow hole in the center and an eccentric core, to 45-degrees. The hybrid fiber tip sensor consists of a quartz cavity and a gas cavity effectively solving the problem of cross sensitivity in dual-parameter sensors. By tracking the shift of the interference spectra of the two FP cavities, simultaneous measurements of temperature and pressure is achieved. With advantages of a compact structure, high spatial resolution, simple fabrication and ability of multi-parameter detection, the sensor is suitable for use in a high temperature and high-pressure simultaneous sensing applications. Furthermore, the fabrication approach ensures consistent size of the FP cavities, making the sensor suitable for mass production.

A Long Period Grating Sensor Based on Micro-taper Eccentric Core Fiber

A Long Period Grating Sensor Based on Micro-taper Eccentric Core Fiber

Sensing characteristics of the F-P cavity on the tip of a microstructured fiber

A Fabry-Pérot interferometer on the tip of a microstructured fiber and its sensing application was demonstrated. The microstructured side hole eccentric core fiber was fabricated using the drilling hole method. The fiber end face was polished to 45° which could reflect the light transverse to the fiber, utilizing the side wall of the air hole as the reflection surface. Sensing abilities of the interferometer were investigated in the experiment. It can work as a probe for liquid RI sensing by simply plunging the fiber tip into the solution being tested, in addition, it can become sensors for different parameters by filling functional materials into the air hole. An example of filling UV curable adhesive into the fiber to be a temperature sensor was demonstrated in the experiment. The sensing structure on the fiber tip shows the advantages of high linearity, easy fabrication and good reproducibility, as a sensor it is also convenient to operate.

Highly sensitive torsion sensor based on helical eccentric dual-core fiber Michelson interferometer

An optical fiber torsion sensor was academically put forward and experimentally demonstrated by applying a Michelson interferometer (MI) based on a helical eccentric dual core fiber (HEDCF). The sensor consists of an eccentric dual core fiber (EDCF), a taper, and a helical structure based on the EDCF. Since there is a large interval between a centric core and an eccentric core of the EDCF, the helical structure can greatly improve the torsion sensitivity of the sensor. When the twisting direction is consistent with the pre-twisting direction, the optical path difference (OPD) of MI negative increases during the twisting process, and the spectral resonance wavelength shifts blue. Experimental results show that the greater the degree of helical addition, the higher the torsional sensitivity. The torsion sensitivity can reach as high as −7.01 nm/(rad/m) in clockwise (CW) direction in the range of 0–9.595 rad/m. Moreover, the satisfactory sensitivity, stable structure and small temperature crosstalk, let it a valuable select in torsion sensing domain, and is promising to be useful for broad applications across engineering fields.

Transportation of cuttings by drilling mud in horizontal wells. Part 2. Numerical results of drilling at optimal rheological properties of mud

The relevance. Ensuring technological equipment operation efficiency when drilling wells with an arbitrary orientation of their wellbores. In particular, the search for productive hydrocarbon reservoirs requires drilling deeper wells with extended horizontal sections, for which the removal of the cuttings bed is the key problem of modern drilling. The aim. Study the features and establish the patterns of cuttings movement through the annulus eccentric space formed by a drill string and well walls under various modes (in-situ) and drilling conditions within the framework of modern mathematical models of hydrodynamics, numerical algorithms and approaches implemented in ANSYS CFD. Optimize the parameters that determine drilling, such as an inclination angle, mass-average velocity and morphology of the inlet rheologically complex viscous flow to form the maximum allowable drilling velocity for various combinations of mud effective viscosity and mixture flow rate. Give practical recommendations for engineers to reduce time, costs and material resources for maintenance and optimization of well cleaning. The object. A well with an eccentric core and an extended horizontal section operating in modes and conditions close to real drilling. The methods. Complex of physical and mathematical analysis and numerical modeling of hydrodynamics and mass transfer in homogeneous and heterogeneous continuous media. The media were widely tested on the class of internal rheological complex flows, the verification of which was carried out under appropriate conditions, performed by other authors when solving problems of drilling and cleaning wells. The results. The paper presents the results of a numerical study of hydrodynamics of a dispersed flow of a rheological complex viscous mixture of a drilling fluid with the properties of a Herschel–Bulkley type fluid and sand particles in wells with an arbitrary generatrix of its wellbore in an eccentric space. The results are required to clarify the features that accompany direct-flow and swirling flow (the moving wall method), identify the patterns in such modes, accounting for which allows for effective cleaning of the annulus. The calculations were performed within the framework of modern mathematical models of the RANS-method and the Euler–Lagrangian approach to describing the motion of heterogeneous media, implemented in the ANSYS CFD software and efficient numerical algorithms for determining intra- and interfacial processes of mass and momentum transfer in mixtures. The authors have determined that when drilling a vertical section, the most effective parameter in terms of cleaning control is the effective viscosity of the mud; the most problematic configurations for cleaning are wells with sloping sections at angles close to the vertical. When drilling a horizontal section, the eccentricity of the drill string creates “the dead” zone of flow and complicates cleaning. This zone should be removed by creating swirling flow conditions through relatively weak rotation of a drill string (30–60 rpm). When drilling inclined sections, it is necessary to reduce a solution viscosity (preferably to the level of fresh water) and increase the flow rate (in this case, to 2 m/s or higher). When drilling a horizontal section, a mud with a viscosity close to fresh water is recommended at flow rates of about 2 m/s (or 640 gpm) at the well inlet and a maximum drilling velocity of 9 m/h.

Misfit stress and energy in composite nanowire with polygonal core

In this article we present for the first time an analytical solution to the boundary-value problem in the classical theory of elasticity for a core-shell cylinder with an eccentric prismatic core having a trapezoidal cross section and subjected to uniform dilatation eigenstrain. In doing so, we represent the trapezoidal prism as a superposition of long straight dilatational lines located along the cylinder axis. The complex potential approach has been employed to satisfy the boundary conditions on the cylinder free surface. Found in a concise and transparent closed form, the elastic stresses exerted by the dilatational line and dilatational prismatic inclusion (of trapezoidal cross section) in cylindrical body are demonstrated with maps. The mean stress is employed to obtain the analytical expression of strain energy stored by the dilatational inclusion in form of regular prism symmetrically placed in cylindrical body. It is proved that the strain energy is identical to the one of cylindrical inclusion with the same cross section area.

Engineering of tunable Au-Ag2S heterostructures: A study of morphology-induced visible-light photocatalytic performance by SERS

Efficient visible-light photocatalysts are essential for energy and environmental sustainability. Many efforts have been devoted to designing diverse heterostructures in the pursuit of high-performance photocatalysts. However, the effect of morphology of the heterostructures on the photocatalytic performance still needs to be further explored. Here, tunable Au-Ag2S heterostructures were synthesized to investigate the morphology-induced photocatalytic performance by surface-enhanced Raman scattering (SERS) spectroscopy. All the Au-Ag2S heterostructures possess remarkable visible-light photocatalytic and SERS activity compared with Au or Ag2S. Moreover, with increasing exposure of the Au component, the Janus heterostructures display better photocatalytic performance than the heterostructures with other morphologies. The possible mechanism is that the axially separated structure enhances the plasmon-induced electron-hole separation and facilitates interfacial charge transfer in the anisotropic heterostructures, owing to a stronger plasmon-enhanced near field. The photocatalytic degradation efficiency of methylene blue by the Au-Ag2S Janus heterostructures reached 93.9% within only 60 s. The photocatalytic degradation rate is 2.38, 1.53 and 1.48 times higher than that of the core–shell, eccentric core–shell-I and eccentric core–shell-II heterostructures. Our work demonstrates that the morphology of the Au-Ag2S heterostructures exhibits a significant effect on the visible-light photocatalytic performance, which opens a new pathway toward the design of heterostructures for high-performance photocatalysis.

Three-dimensional micro displacement sensor based on fiber SPR mechanisms.

Three fiber micro displacement sensors can be combined to realize three-dimensional (3D) displacement sensing, but the system is complex. In this paper, a 3D displacement sensor based on fiber SPR was proposed, which was composed of displacement fiber and sensing fiber. By cascading the eccentric dual-core fiber and graded multimode fiber, the displacement fiber was realized. The V-groove was processed in the vertical and horizontal directions of the graded multimode fiber, and the inclined SPR sensing areas were fabricated to realize the sensing fiber. A straight beam from the middle core of the displacement fiber contacted the vertical V-groove inclined plane of the sensing fiber to realize the Y axis (up and down) direction micro displacement, contacted the horizontal V-groove inclined plane of the sensing fiber to realize the Z axis (front and back) direction micro displacement sensing. An oblique beam from the eccentric core of the displacement fiber cooperated with the sensing fiber to realize the micro displacement sensing in the X-axis (left and right) direction. The testing results indicate that the fiber SPR 3D micro displacement sensor can sense micro displacement in the X axis, Y axis and Z axis, and the wavelength sensitivity is 0.148 nm/µm, -3.724 nm/µm and 3.543 nm/µm, respectively. The light intensity sensitivity is -0.0014a.u./µm, -0.0458a.u./µm and -0.0494a.u./µm, respectively. When adjusting the parameters of eccentric dual-core fiber, the larger the core distance is, the greater the displacement sensitivity in the X-axis direction of the sensor is, and the smaller the detection range is. The proposed sensor can realize 3D micro displacement sensing by itself, which is expected to be used in the field of 3D micro displacement measurement and 3D space precision positioning.

Single-Hole Janus Hollow Sphere.

Cross-linked epoxy resin (EP) single-hole Janus hollow spheres are prepared by cross-linking induced phase separation within an emulsion droplet and selective modification. The droplet is composed of an EP oligomer, toluene, and hexadecane. 2-Ethyl-4-methylimidazole is used as the cross-linker added to the aqueous phase. During the cross-linking, hexadecane forms an eccentric core in the cross-linked EP sphere. A single hole forms across the shell after dissolving the solvents, and a single-hole hollow sphere is achieved. The hole and cavity size are controlled by adjusting the solvent content and cross-linker concentration. Furthermore, frozen wax is used as the core material instead of hexadecane to effectively protect the sphere's interior surface. Selective modification of the exterior and interior surfaces is thus permitted. As an example, a responsive single-hole Janus hollow sphere is prepared by the favorable growth of a silica-polyoxyethylene composite layer onto the exterior surface and a selective grafting of poly(2-diethylaminoethyl methacrylate) (PDEAEMA) by atom-transfer radical polymerization (ATRP) onto the interior. The Janus sphere is water-dispersible and controllably captures and releases oil from the aqueous environment as triggered by the pH value.

Dual-channel refractive index sensor based on coupling between LP01 and LP11 modes in the tapered hole-assisted dual-core fiber.

We propose a refractive index (RI) sensor based on a tapered hole-assisted dual-core fiber (HADCF). The sensor is fabricated by splicing a tapered HADCF between two single-mode fibers and operates on the coupling between the fundamental mode and the low-order mode in two cores. The HADCF is tapered to meet the phase matching condition between the fundamental mode (LP01) in the central core and the low-order mode (LP11) in the eccentric core. The tapered waist of the fiber becomes thinner; the coupling wavelength has a blue shift. Glycerin solutions of different RIs were injected into the air hole. The RI sensitivity of 936.69 nm/RIU is obtained in the RI range of 1.335-1.360. The multi-channel RI sensor cascaded by HADCFs with different taper lengths is obtained and can simultaneously measure the RI of different solutions. The proposed device has the advantages of high sensitivity, simple structure, and stable performance. The special microfluidic channel in the HADCF can protect the tested solution from external environmental pollution.

High sensitivity detection of SARS-CoV-2 by an optofluidic hollow eccentric core fiber.

Since the outbreak of coronavirus disease 2019 (COVID-19), efficient real-time monitoring has become one of the challenges faced in SARS-CoV-2 virus detection. A compact all-fiber Mach-Zehnder interferometer optofluidic sensor based on a hollow eccentric core fiber (HECF) for the detection and real-time monitoring of SARS-CoV-2 spike glycoprotein (SARS-CoV-2 S2) is proposed, analyzed and demonstrated. The sensor is comprised of fusion splicing single mode fiber (SMF), hollow core fiber (HCF) and HECF. After the incident light passes through the HCF from the SMF, it uniformly enters the air hole and the suspended micrometer-scale fiber core of the HECF to form a compact all-fiber Mach-Zehnder interferometer (MZI). HECF is side polished to remove part of the cladding that the suspended fiber core can contact the external environment. Subsequently, the mouse anti SARS-CoV-2 S2 antibody is fixed on the surface of the suspended-core for the sake of achieving high sensitivity and specific sensing of SARS-CoV-2 S2. The limit of detection (LOD) of the sensor is 26.8 pM. The proposed sensor has high sensitivity, satisfactory selectivity, and can be fabricated at low cost making it highly suitable for point-of-care testing and high-throughput detection of early stage of COVID-19 infection.

High-sensitivity two-axis vector bending sensor based on side-grooved long period grating in eccentric core fiber

A novel vector bend sensor based on side-grooved Long period grating (SG-LPG) inscribed on eccentric core fiber (ECF) was proposed and investigated. The core of the ECF is close to the surface of the fiber, which makes it very convenient to fabricate different SG-LPGs in ECF by CO2 laser with little damage. Since the direction of the SG-LPG deviates from the direction of the side core of the ECF, the sensor can identify bending directions on two orthogonal axes. At the same time, the strong refractive index modulation caused by grooves makes SG-LPG very sensitive to bending. In the curvature range of 0–2.52 m−1, the bend sensitivity in four directions reaches 27.23 nm/m−1, −25.76 nm/m−1, 14.74 nm/m−1 and −16.83 nm/m−1, respectively. Due to the simple structure, convenient fabrication, high sensitivity, and multi vectors bending detection characters, the sensor has potential in bending measurement.

Tilted Long Period Grating Inscribed in Eccentric Dual Core Fiber for Highly Sensitive Torsion Sensing

We proposed and experimentally investigated the torsion sensing performance of tilted long period gratings (TLPG) based on eccentric dual core fiber (EDCF). The EDCF is composed of a centric core and an eccentric core with a large separation. The asymmetrical structure of the EDCF and the high refractive index modulation of TLPG can bring some directional and sensitivity advantages to structure. We tested the torsional sensing in two optical channels of EDCF with different grating parameters and found both cores of EDCF can recognize the torsion direction. When the tilt angle of the TLPG is 80°, the maximum torsional sensitivity of the centric core and eccentric core are −0.381 nm/(rad/m) and 0.812 nm/(rad/m), respectively, which are 7 times and 16 times higher than similar TLPG inscribed in normal single mode fiber. In this condition, this sensor has good structural stability and high torsion sensitivity, and has great potential in multi-channel sensing applications.

Investigation on drag reduction of aqueous foam for transporting thermally produced high viscosity oil

An innovative idea is proposed for facilitating the transportation of thermally produced high-viscosity oil by injecting temperature tolerant aqueous foam. To this aim, experimental investigations of the flow characteristics of heated highly viscous oil flowing through a 25 mm i.d. horizontal rough-wall tempered borosilicate glass pipe were conducted. Measurements were made for the superficial oil and foam velocities in the range of 0.05–0.40 m/s and 0.04–0.39 m/s, respectively. Eccentric core annular flow configurations detected by a high-speed camera were found to be particularly dominant throughout the entire tested range. A two-fluid, three-zone mechanistic model for horizontal foam-oil flows was implemented for the case of shear thinning power-law fluid in the annulus, which is in accordance with the foam rheological behavior at the tested elevated temperature. Good agreement was achieved between the predicted and measured data over a wide range of operational conditions. When a complete foam annulus encapsulating the oil core is formed, a critical value of input foam volume fraction can be determined for the maximum drag reduction ratio. An optimal oil core-to-pipe radius ratio range was determined for the highest oil-transport operational coefficient. The drag reduction performance of the tested hot oil-foam system is better than that obtained with the oil-foam system employed at room temperature.

Photochemical micromotor of eccentric core in isotropic hollow shell exhibiting multimodal motion behavior

Adaptive motion behavior in response to different environmental stimuli is ubiquitous in biology and enables creatures to achieve a diversity of complex tasks, but not typically observed in synthetic systems. Here we propose a design of chemically-powered micromotors actively performing multimodal motion behaviors with the external stimulus changing. They have isotropic outer surfaces but inherent inner mass asymmetry, such as eccentric core-in-hollow shell TiO2 (E-TiO2) microspheres. Their motion behavior can be spontaneously transformed among random Brownian propulsion (stochastic walk), negative phototaxis (moving against incident light), and negative photogravitaxis (moving against gravity) when the light intensity, illumination direction, or fuel concentration change. At a low light intensity and/or low H2O2 fuel concentration, the E-TiO2 micromotors perform directional movement away from light based on the dominated diffusiophoresis by the photocatalytic reaction over the isotropic shell. With the increase of light intensity or fuel concentration, there are more and more photons or fuels to reach the eccentric core and the contribution of the photocatalytic reaction over it to the diffusiophoresis gradually becomes dominant. In this case, the E-TiO2 micromotors perform stochastic walks near the substrate due to their Brownian random rotational reorientations. The micromotors are single component, have low density, and can be synthesized in a large scale and at a low cost. This work will facilitate the development of multifunctional micro/nanomotors with varying behaviors and functions depending on environmental cues, e.g., enabling efficient search and delivery operations.