Conical Fiber Research Articles

Capillary-driven migration of droplets on conical fibers

A droplet placed on a hydrophilic conical fiber tends to move toward the end of larger radii due to capillary action. Experimental investigations are performed to explore the dynamics of droplets with varying viscosities and volumes on different fibers at the microscale. Droplets are found to accelerate initially and subsequently decelerate during migration. A dynamic model is developed to capture the dynamics of droplet migration, addressing the limitations of previous equilibrium-based scaling laws. Both experimental results and theoretical predictions indicate that droplets on more divergent fibers experience a longer acceleration phase. Additionally, gravitational effects are pronounced on fibers with small cone angles, exerting a substantial influence on droplet migration even below the capillary scale. Moreover, droplets move more slowly on dry fibers compared to those prewetted with the same liquid, primarily attributed to increased friction. The experiments reveal the formation of a residual liquid film after droplet migration on dry fibers, leading to considerable volume loss in the droplets. To encompass the intricacies of migration on dry fibers, the model is refined to incorporate a higher friction coefficient and variable droplet volumes, providing a more comprehensive depiction of the underlying physics.

High sensitivity fiber SPR sensor based on a spiral coarse cone structure.

A fiber SPR sensor can achieve rapid and portable detection of trivalent arsenic ions (As3+) in drinking water or food, but their sensitivity and detection limit need to be further improved and developed toward specific detection. This article proposed the implementation of the SPR sensor using a biased core fiber spiral coarse cone structure. The fine core of the biased core fiber was used to reduce the mode of transmitted light. By controlling the pitch of the spiral core to control the SPR incidence angle, a significant increase in the sensitivity of the fiber SPR sensor was achieved. Meanwhile, the harmless glutathione (GSH) was modified on the surface of the sensing gold film to achieve the specific detection of As3+. The experimental results indicate that the spiral coarse cone fiber SPR sensor proposed in this article has a detection sensitivity of 32.48 nm/ppb for As3+, with a detection limit as low as 0.011 ppb, meeting the detection requirements of the World Health Organization for As3+ in water, which provides a new feasible solution for fast, portable, and highly sensitive detection of metal ions in water and food.

An Ultra‐Smooth rGO Nano‐Thin Film from a Homogeneous Thin Liquid Film Confined by a Conical Fiber Array: Toward the Highly Sensitive Pressure Sensor

AbstractReduced graphene oxide (rGO) thin films have demonstrated various advantages in flexible electronics. So far, solution processes are widely used for making rGO thin films for their mild operation conditions and low cost. However, wrinkles are frequently formed due to the capillary contraction during drying, which severely deteriorates the conductivity and the transparency of rGO thin films. Here, an ultra‐smooth rGO nano‐thin film, featuring wrinkle‐free and a rather low surface roughness of 1.38 nm is developed, which is attributable to a steady and homogeneous thin liquid film confined by a conical fiber array. The thin liquid film facilitates both in‐plane stacking of nanosheets and reducing the buried solvent under nanosheets. Notably, with the capillary flow replenishing the tri‐phase contact line evaporation, a semi‐dry film near the tri‐phase contact line is produced, that enables the force equilibrium of multi‐directional capillary forces on dispersed nanosheets for depositing a wrinkle‐free nanofilm. The as‐prepared rGO nanofilm gives a low sheet resistance of 8.3 kΩ sq−1 and a high transmittance of 91.9%, showing better performances than other reported rGO nanofilms. On this basis, it is demonstrated that a high‐sensitive pressure sensor with a detection limit as low as 0.02 Pa, highlighting the solution‐processed innovative ultra‐smooth 2D nanomaterial thin films, and devices.

Efficient and stable coupling to nanophotonic waveguides and resonators in stringent environments

Using conical optical fibers, we explore new methods for coupling light to nanophotonic structures operated in constrained environments. With a single-sided conical fiber taper, we demonstrate efficient coupling to an on-chip nanophotonic bus waveguide immersed in a liquid. In the aim of coupling light into a target whispering gallery disk resonator, we then replace such on-chip nanophotonic bus waveguide with two conical fibers joined face to face. This latter approach leads to highly efficient coupling superior to 90% and is shown to be stable within a vibrating pulse tube cryostat operating at low temperatures. It is demonstrated in the telecom band and in the near infrared close to 900 nm of wavelength. Conical fiber methods hence enable reaching the coupling performances required in quantum optics or sensing experiments, even in stringent environments where signal-to-noise had remained a challenge.

Spiral cone fiber SPR sensor for detecting ginsenoside Rg1

The conical fiber SPR sensor is easy to manufacture and has been used in biochemical detection research, but it has the problem of structural fragility. This article proposes a spiral cone fiber SPR sensor, which introduces a spiral structure on the 76µm fiber coarse cone, achieving good coupling of the core mode into the cladding mode, and improving the physical strength and practicality of the cone-shaped fiber SPR sensor. By modifying the target protein on the surface of the sensor gold film, specific detection of ginsenoside Rg1, an active ingredient of traditional Chinese medicine ginseng, was achieved. The detection sensitivity was 0.138 nm/(µm/ml) and the detection limit was 0.22µm/ml. The proposed spiral cone fiber SPR sensor provides a new scheme for the specific detection of active ingredients in traditional Chinese medicine, which is structurally stable and physically strong.

Single vesicle chemistry reveals partial release happens at the mechanical stress-induced exocytosis

Neuronal activity can be modulated by mechanical stress in the central nervous system (CNS) in neurodegenerative diseases, for example Alzheimer's disease. However, the impact of mechanical stress on chemical signal transmission, especially the storage and release of neurotransmitter in neuron vesicles, has not been fully clarified. In this study, a nanotip conical carbon fiber microelectrode (CFME) and a disk CFME are placed in and on a cell, respectively. The nanotip conical CFME functions for both the mechanical stress and the quantification of transmitter storage in single vesicles, while the disk CFME is used to monitor the transmitter release during exocytosis induced by mechanical stress at the same cell. By comparing the vesicular transmitter storage with its release during mechanical stress-induced exocytosis at the same cell, we find the release ratio of transmitter in chromaffin cells varies from 27 % to 100 %, while for PC12 cells from 30 % to 100 %. Our results indicate that the exocytosis of cells responding to mechanical stress shows individual difference obviously, with a significant population exhibiting partial release mode. The variation of Ca2+ channels and mechanosensitive ion channels on cell membrane may both contribute to this variation. Our discovery not only shows mechanical stress can change the transmission of cellular chemical signals at the vesicle level, but also provides an important reference perspective for the study of nervous system regulation and nervous system diseases.

An Ultra‐High Transparent Electrode via a Unique Micro‐Patterned AgNWs Crossing‐Network with 3.9% Coverage: Toward Highly‐Transparent Flexible QLEDs

AbstractMicro‐patterning silver nanowires (AgNWs) via solution processes is vital in making high‐performance transparent flexible electrodes (TFE) that have been widely used in optoelectronic devices. However, it has suffered from the limitation of a trade‐off relationship between the coverage and the arrangement of AgNWs, which determine the transparency and the conductivity, respectively. Here, unique AgNWs micro‐patterns, featuring as the crossing‐grid of high‐resolution and highly‐aligned AgNWs micro‐lines, which enable the micro‐pattern highly cross‐aligned with a limited 3.9% coverage, are developed. Consequently, a TFE with an ultra‐high transmittance over 98.5% and a sheet resistance of 25.5 Ω sq−1 is developed. Guided by the unit of triple conical fibers, AgNWs are controllable transferred onto the target area, leaving a line with a width‐resolution up to 2 µm. Simultaneously, AgNWs are aligned under the synergistic effect of both the solution‐shearing and the tri‐phase contact line confinement. Using the as‐developed TFE as either the top or the bottom electrode, a transparent quantum dot light‐emitting diode (T‐QLED) with a transmittance of 89.8%, as well as a flexible T‐QLED with a transmittance of 92.8% are demonstrated, much higher than those of T‐QLEDs reported. It is envisioned that the result would inspire the fabrication of high‐performance transparent optoelectronic devices.

Fabrication and characterization of weld attributes in hot gas welding of alkali treated hybrid flax fiber and pine cone fibers reinforced poly-lactic acid (PLA) based biodegradable polymer composites: studies on mechanical and morphological properties

The contemporary times have witnessed a lot of interest in fabricating green composites because of its biodegradability, durability, affordability, ease of manufacturing and its potential to replace existing commercial goods in the field of engineering applications. The green composites are envisaged to replace synthetic polymer-based composites since the green composites are fabricated using the biodegradable polymers reinforced with natural fibers. In this research work, Flax Fiber and Pine Cone Fibers are reinforced in Poly-lactic Acid (PLA) matrix. The green composites are fabricated using compression moulding technique in different nominations as per the weight fraction such as (90:10), (80:20) and (70:30). It was noticed that a higher tensile strength of 27 MPa is observed in case of group 2 (80:20) specifically for the composite having 80% of matrix and 14% flax and 6% pine cone fibers. An IoT based automatic hot gas welding method was used to join the fibers by considering various input parameters like stand of distance, weld rate, specimen groove geometry, and composition. The mechanical testing of the weld specimens was carried. It was observed that the weld joints having higher stand of distance were observed to have less tensile strength as compared to others and the fracture points of such specimens were observed to be at the weld bead. SEM analysis of the fracture point validated the observations from the mechanical characterization.

The dynamic behavior of a self-propelled droplet on a conical fiber: A lattice Boltzmann study

In this paper, the dynamic behavior of a self-propelled droplet along a conical fiber is simulated by using an improved lattice Boltzmann color-gradient method. This method is developed on the basis of our recently developed density ratio model [Zhang et al., Int. Commun. Heat Mass Transfer, 137, 106284 (2022).], but a wetting boundary condition is added to account for the moving contact line on an arbitrary solid surface. First, this method is validated against the analytical droplet shapes and contact angles for droplets surrounded by matrix fluids of different densities on flat and spherical surfaces, and the spontaneous transport of a droplet on a conical fiber. This method is then adopted to systematically study the effects of the Bond number (Bo), surface wettability (θ), cone hemi-angle (α), and droplet volume on the droplet dynamic behavior. In each case, the results show that the droplet climbing velocity first increases and then decreases, and a velocity fluctuation is observed, which is due to that the apparent receding and advancing contact angles do not simultaneously reach the equilibrium contact angle. As droplet volume increases, the equilibrium droplet height monotonically increases. As Bo or θ increases, the droplet climbing height and the wetting area both decrease. We also found that the equilibrium climbing height first increases and then decreases with α, and its maximum is reached around α=2.5°.

The Explanation of Photopic Luminous Efficiency Curve by Using Both of the Cones' Optical Fiber Coupling Effects and the Absorption of L Cones.

In this paper, we build four-part cone models to explore the coupling effect of seven cone fiber couplers. Moreover, this is the first study of the coupling effect of four layers of biological couplers in animals and other biological lives. We simulate the four layers cone couplers by using the beam propagation method, and we assume the input beam is located at the outer fiber of the central cone. Our simulation results showed that there are two wavelength regions (short and long wavelength regions) with the strongest coupling, where the most power of input optical powers of the central cones will transfer to the six surrounding cones after transmitting through the four layers of cone couplers. However, within a wavelength region of ±75 nm near to the peak wavelengths, located in the yellow-green wavelength range, the splitting ratios at the output of the outer segment of the central cone are always greater than the sum of the splitting ratios of the six surrounding cones. These cone couplers may play an important role in color preprocessing (e.g., doing opponent color processing partially). The cone fiber coupler effect and light absorption of cones are considered separately in our models. By taking account of both the cone fiber coupling effect and absorption of outer segment of L cone, we find the multiplication of the relative optical power of cone couplers, the spectral sensitivity data of the L cone, and a normalized coefficient that matches with the photopic luminous efficiency of the human eye well. This is the attempt to use both the cone fiber coupling effect and the absorption of L cones to explain the photopic luminous efficiency. The splitting ratios of the central cones are greater than 80% at peak wavelengths located in the yellow-green wavelength range, and this can help to explain why the human eye is more sensitive to green light.

Natural fibers as an alternative to synthetic fibers in the reinforcement of phosphate sludge-based geopolymer mortar

Geopolymers are a kind of material of great technological and ecological interest thanks to their high mechanical properties and their ability to be produced from industrial by-products. However, like all cementitious matrices, geopolymers have a fragile character and suffer from low ductility. To overcome this challenge while staying environmentally conscious, the present research focuses on the efficiency of using natural fibers instead of synthetic fibers in the reinforcement of geopolymer mortars based on phosphate industry by-products. Geopolymer mortar composites were prepared by incorporating high contents of pine cone fibers (NF) and glass fibers (GF) into a geopolymer mortar matrix based on treated phosphate sludge, metakaolin, and sand. Pine cone fibers reinforced composites were assessed and compared to glass fibers reinforced composites and control mortar in terms of structural, physical, and mechanical properties. The structural analysis revealed that the prepared mortars consist of a continuous three-dimensional network characteristic of a geopolymer matrix without undesirable interactions between the used fibers and the mortar matrix. Density, porosity, and water absorption studies indicate that pine cone fibers created fewer defects in the geopolymer mortar matrix than glass fibers, and that NF-reinforced composites are more resistant to moisture than GF-reinforced ones by about 2%. The results of the mechanical properties showed that the addition of fibers, whether natural or synthetic, decreases the compressive strength and significantly increases the flexural strength. However, Although the flexural strength rises with the fiber content in the matrix, the fiber content of 50 wt% sand volume fraction was the limit, since beyond this content, the workability and flowability of the composites notably decrease. Overall, when both mechanical properties are considered, as well as the ecological and economic impacts, it can be stated that pine cone fibers could potentially replace synthetic fibers in the reinforcement of phosphate sludge-based-geopolymer mortars.

Magnetic Field Sensing of Conical Optical Fibers Based on PVA/Fe3O4 Hydrogel

Magnetic Field Sensing of Conical Optical Fibers Based on PVA/Fe3O4 Hydrogel

The effectivity of probiotic containing Bacillus spp. applicated in the rearing of mud crab Scylla tranquebarica larvae to produce crablet

Probiotic bacteria in larvae rearing is expected to suppress pathogenic bacteria and improve water quality. The research aimed to determine the effectivity of probiotic bacteria containing Bacillus subtilis and B. licheniformis on larval rearing of purple mud crab Scylla tranquebarica to produce crablet. The larvae were stocked in nine units of conical fiber tank, fed Rotifers, Brachionus plicatilis, and nauplii Artemia sp. The probiotics tested, namely, A). RICA-4, containing the bacterium Bacillus subtilis, B). RICA-5 containing B. licheniformis, C). A combination of probiotics RICA-4 and RICA-5. The administration of each probiotic with a density of 108 CFU g−1 (5 mg L−1) was given to the water media for larvae rearing. The lowest nitrite and Total Organic Matter in the zoea stage were found in treatment B. At the megalopa stage, treatment B’s lowest TOM concentration occurred and was significantly different (p<0.05) from treatment C. On the other hand, the highest population of Vibrio spp (5.5x103 CFU mL−1) was obtained in treatment A. In contrast, treatment C had the highest bacteria population (4.8x104 CFU mL-1). On day 19, the megalopa in treatment B was more abundant than in treatments A and C causing crablet production in treatment B (280.5±47.50 ind. tank −1) was significantly higher (p<0.05) than crablet production in treatment C (196.5±29.50 ind. tank −1) and A (161.0±21.00 ind. tank −1). Therefore, improving water quality in treatment B may have an important factor in enhancing crablet production.

A Temperature and Strain Dual-Parameter Sensor Based on Conical Four-Core Fiber Combined With a Multimode Fiber

A temperature and strain dual-parameter sensor based on conical four-core fiber (FCF) combined with multimode fiber (MMF) is presented. A sensor based on Mach–Zehnder interferometry is prepared by using single-mode fiber (SMF)–MMF–FCF–SMF and tapering at the fusion point between FCF and SMF. When the temperature and strain change, the length and refractive index of the fiber change due to thermal and elastic effects. Based on the corresponding function relationship and coefficient matrix method, the temperature and strain dual-parameter matrix equation of the sensor can be obtained. The results show that the red shift of the transmission spectrum occurs with the increase of temperature in the range of 40 °C–90 °C, and the maximum temperature sensitivity is 85.45 pm/°C. At the strain range of 0– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$800~\mu \varepsilon $ </tex-math></inline-formula> , the blue shift occurs in the transmission spectrum with the increase of the strain, and the maximum strain sensitivity is −6.76 pm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> . Finally, the matrix equation of the dual-parameter sensor is obtained based on the experimental results. The sensor is simple to make and has high sensitivity. It can measure the temperature and strain parameters in the environment of the micro-magnetic field and micro-electric field.

Nanodiamond-Based Optical-Fiber Quantum Probe for Magnetic Field and Biological Sensing.

Owing to the unique electronic spin properties, nitrogen-vacancy (NV) centers hosted in diamond have emerged as a powerful quantum tool for detecting various physical parameters and biological species. In this work, an optical-fiber quantum probe, configured by chemically modifying nanodiamonds on the surface of a cone fiber tip, is developed. Based on the continuous-wave optically detected magnetic resonance method and lock-in amplification technique, it is found that the sensing performance of probes can be engineered by varying the nanodiamond dispersion concentration and modification duration during the chemical modification process. Combined with a pair of magnetic flux concentrators, the magnetic field detection sensitivity has reached 0.57 nT/Hz1/2@1 Hz, a new record among the fiber magnetometers based on nanodiamonds. Taking Gd3+ as the demo, the capability of probes in paramagnetic species detection is also demonstrated experimentally. Our work provides a new approach to develop NV centers as quantum probes featuring high integration, multifunction, high sensitivity, etc.

Bioinspired Robust Water Repellency in High Humidity by Micro-meter-Scaled Conical Fibers: Toward a Long-Time Underwater Aerobic Reaction.

Superhydrophobic surfaces have suffered from being frequently penetrated by micro-/nano-droplets in high humidity, which severely deteriorates their water repellency. So far, various biological models for the high water repellency have been reported, which, however, focused mostly on the structural topology with less attention on the dimension character. Here, we revealed a common dimension character of the superhydrophobic fibrous structures of both Gerris legs and Argyroneta abdomens, featured as the conical topology and the micro-meter-scaled cylindrical diameter. In particular, it can be expressed by using a parameter of rp/l > 0.75 μm (r, l, and p are the radius, length, and apex spacing between fibers, respectively). Drawing inspiration, we developed a superhydrophobic micro-meter-scaled conical fiber array with a rather high rp/l value of 0.85 μm, which endows ultra-high water repellency even in high humidity. The micro-meter-scale asymmetric confined space between fibers enables generating a big difference in the Laplace pressure enough to propel the condensed dews away, while the tips help pin the air pocket underwater with a rather long life over 41 days. Taking advantage, we demonstrated a sustainable underwater aerobic reaction where oxygen was continuously supplied from the trapped air pocket by a gradually diffusing process. As a parameter describing both the dimension character and structural topology, the rp/l offers a new perspective for fabricating superhydrophobic fibrous materials with robust water repellency in high humidity, which inspires the innovative underwater devices with a robust anti-wetting performance.

Fiber optic sensor for nondestructive detection of microbial growth on a silk surface.

To nondestructively detect the mold growth process on silk, a coaxial concave reflection conical fiber optic sensor was developed using conical quartz fibers, fiber connectors, fiber couplers, and a plastic fixator. We established a theoretical model of this sensor and studied the influence of its structural parameters on its sensitivity, characterized the morphology of Aspergillus niger, and detected its growth process on a silk surface. A linear relationship between the sensor's output signal and the mold height was found. The sensor sensitivity, maximum detection error, and low limit of detection were 2.4 E-5 AU/µm, 7.83%, and 10 µm, respectively.

Electrochemical On-Site Switching of the Directional Liquid Transport on a Conical Fiber.

Directional liquid transport (DLT), especially that proceeding on a conical fiber (DLT-CF), is an important mass-transfer process widely used both by natural organisms and in practical applications. However, on-site switching of the DLT-CF remains a challenge due to the nontunable driving force imparted by the structural gradient, which greatly limits its application. Here, unprecedently, a facile electrochemical strategy is developed for reaching the on-site switchable DLT-CF, featuring in situ control and fast response. Depending on the poised electric potential, the droplet can either move directionally or be pinned at any position for a tunable duration time, exhibiting completely different moving characteristics from the traditional DLT-CF with no control. It is proposed that the surface hysteresis resistance, closely related to both the surface hydrogen-bonding network and the droplet topology on the fiber, can be largely altered electrochemically. The tunable hysteresis resistance works synergistically with the conical-structure-induced Laplace pressure to on-site tune the forces acting on the droplet, leading to various controllable DLTs-CF, including those with tunable distance and direction, array manipulation, and assembly line processing of droplets. The strategy is applicable for versatile liquids, offering a general approach for controllable liquid transport in fibrous systems.

A generalized shear-lag theory for elastic stress transfer between matrix and fibres having a variable radius

A generalized shear-lag theory for fibres with variable radius is developed to analyse elastic fibre/matrix stress transfer. The theory accounts for the reinforcement of biological composites, such as soft tissue and bone tissue, as well as for the reinforcement of technical composite materials, such as fibre-reinforced polymers (FRP). The original shear-lag theory proposed by Cox in 1952 is generalized for fibres with variable radius and with symmetric and asymmetric ends. Analytical solutions are derived for the distribution of axial and interfacial shear stress in cylindrical and elliptical fibres, as well as conical and paraboloidal fibres with asymmetric ends. Additionally, the distribution of axial and interfacial shear stress for conical and paraboloidal fibres with symmetric ends are numerically predicted. The results are compared with solutions from axisymmetric finite element models. A parameter study is performed, to investigate the suitability of alternative fibre geometries for use in FRP.

Multiple droplets on a conical fiber: formation, motion, and droplet mergers.

Small droplets on slender conical fibers spontaneously move along the fiber due to capillary action. The droplet motion depends on the geometry of the cone, the surface wettability, the surface tension, the viscosity, and the droplet size. Here we study with experiments and numerical simulations, the formation, spontaneous motion, and the eventual merger, of multiple droplets on slender conical fibers as they interact with each other. The droplet size and their spacing on the fibre is controlled by the Plateau-Rayleigh instability after dip-coating the conical fiber. Once these droplets are formed on the fiber, they spontaneously start to move. Since droplets of different size move with different speeds, they effectively coarsen the droplet patterning by merging on the fiber. The droplet merging process affects locally the droplet speed and alters the spatiotemporal film deposition on the fiber.