Morphology Of Electrospun Fibers Research Articles

The effect of electric field uniformity on electrospun jet evolution and fiber morphology

Electric field distribution has a considerable impact on jet motion and resultant fibers’ diameter and morphology in electrospinning process. This study aims to explore the effect of electric field uniformity on jet evolution and fiber morphology by using auxiliary electrodes. Four disc auxiliary electrodes with different external diameters were designed. A high-speed photography equipment was employed to capture the jet motion. The morphology the fibers obtained from different locations of the jet were observed by the SEM to investigate jets evolution under different electric fields. The three-dimensional electric field were calculated by the ANSYS Maxwell software to simulate and quantify the electric field distribution throughout the electrospinning process. The results show that the larger diameter of the auxiliary electrode creates more uniform electric field distribution, smaller jet straight lengths, larger whipping amplitude, and lower the jet velocity. These factors result in finer and more uniform fibers. It was found that the morphology of fiber surface, beads shape and size also influenced by the uniformity of electric field distribution. This research indicates that a controllable uniform electric field was essential in preparing high-performance fibers.

Remnant polarization and structural arrangement in P(VDF-TrFE) electrospun fiber meshes affect osteogenic differentiation of human mesenchymal stromal cells

Many tissues and cells are influenced by mechano-electric stimulation, thus the application of piezoelectric materials has recently received considerable attention in tissue engineering. This report investigated electrospun fiber meshes based on poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] as instructive biomaterials for osteogenic differentiation of human mesenchymal stromal cells (hMSCs). The influence played by methyl ethyl ketone (MEK), used as a solvent in place of dimethylformamide (DMF)/acetone mixture, and the effect of rotating velocity of the electrospinning collector on fiber morphology, mechanical and piezoelectric properties were studied. The solvent had noticeable effects on morphology and piezoelectric properties of electrospun fibers, with MEK outperforming DMF/acetone. By increasing the collector velocity up to 4000 rpm, the fiber diameter reduced and the mutual alignment of the fibers increased, corresponding to enhanced mechanical properties and piezo-active β-phase content. However, as a consequence of the diverse mechanical properties of random and aligned fibrous architectures, which ultimately affected the piezoelectric properties, randomly-oriented fibers exhibited higher remnant piezoelectric properties (Vout and d31 piezoelectric coefficient) than aligned ones. On these scaffolds, hMSCs showed an excellent capability of early osteogenic differentiation, leading to high calcium production. Fiber surface topology, fiber mesh morphology and remnant piezoelectric properties played a determinant role on hMSC osteogenic commitment.

Metal‐organic framework‐based nanofibrous film for two different modes of triboelectric nanogenerators

AbstractMetal‐organic frameworks (MOFs) are nanomaterials with engineered chemical structures, offering remarkable properties. However, their limited film‐formation capability hinders their integration into triboelectric nanogenerators (TENGs). This study proposes a simple yet effective solution to overcome this challenge by employing electrospinning techniques to integrate the zeolitic imidazolate framework (ZIF‐8) into an easy‐to‐use nanofibrous mat. ZIF‐8 has high surface potential, a unique cubical structure, and an easy fabrication process that makes it an ideal material for TENGs. By incorporating ZIF‐8 into the electrospinning solution, significant improvements are achieved in the electropositivity of the resulting nanofibers. It leads to notable changes in the shape, morphology, and roughness of electrospun fibers, consequently enhancing the overall performance of the TENG. The results indicate that utilizing the ZIF‐based electrospun mat as a tribo‐positive material can increase transferred charges between electrodes by more than 100%. Utilizing the MOF‐based nanofibrous mat, this study also introduces a novel rotary TENG that works based on a mode of TENG operation called rolling mode. The reliable charge generation by the proposed rolling system reveals that this mode of TENG operation could be a superb alternative for traditional TENG modes, like contact/separation or sliding, which cause high levels of mechanical stress due to harsh physical impact or friction.

A Study of the Relationship between Polymer Solution Entanglement and Electrospun PCL Fiber Mechanics.

Electrospun fibers range in size from nanometers to micrometers and have a multitude of potential applications that depend upon their morphology and mechanics. In this paper, we investigate the effect of polymer solution entanglement on the mechanical properties of individual electrospun polycaprolactone (PCL) fibers. Multiple concentrations of PCL, a biocompatible polymer, were dissolved in a minimum toxicity solvent composed of acetic acid and formic acid. The number of entanglements per polymer (ne) in solution was calculated using the polymer volume fraction, and the resultant electrospun fiber morphology and mechanics were measured. Consistent electrospinning of smooth fibers was achieved for solutions with ne ranging from 3.8 to 4.9, and the corresponding concentration of 13 g/dL to 17 g/dL PCL. The initial modulus of the resultant fibers did not depend upon polymer entanglement. However, the examination of fiber mechanics at higher strains, performed via lateral force atomic force microscopy (AFM), revealed differences among the fibers formed at various concentrations. Average fiber extensibility increased by 35% as the polymer entanglement number increased from a 3.8 ne solution to a 4.9 ne solution. All PCL fibers displayed strain-hardening behavior. On average, the stress increased with strain to the second power. Therefore, the larger extensibilities at higher ne also led to a more than double increase in fiber strength. Our results support the role of polymer entanglement in the mechanical properties of electrospun fiber at large strains.

Effect of Ce3+ on the morphology, composition, and thermal properties of single and core-shell polyethylene oxide electrospun fibers

Cerium polymeric composites have novel applications in fuel cells, optical devices, gas sensors, catalysis, ultraviolet absorbers, hydrogen storage materials, and biomedicines. This study reports the fabrication of low-cost electrospun single and core-shell polyethylene oxide (PEO) doped with Cerium fibers fabricated in two moisture ambients. Scanning electron microscopy and atomic force microscopy revealed that obtaining the thinnest average fiber diameter requires 47-52 %RH and 2 % Cerium dopant. Using a PEO capping (shell fiber) allows the increment of Cerium in the inner matrix (core-fiber) to produce non-beading continuous fibers with 3.5% of the dopant. The undoped single or core-shell fibers presented a 52.7 to 54.2 % crystallinity, indecently of relative humidity used during the fabrication process. In contrast, the use of Cerium dopant up to 2% induces an increase in their crystallinity due to the formation of Ce-O species, enhancing their thermal properties, regardless of the moisture during manufacturing as was found with Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis.

The correlation of sulfonation reaction kinetics with the degree of sulfonation (DS) and its effects on microstructure and morphology of electrospun fibers for the membrane of fuel cells.

Sulfonation is among the frequently used surface modification methods to endow new surface properties on polymer fibers. Direct sulfonation is the simplest chemical modification via incorporation of sulfonate functional groups onto fibers' surfaces at ordinary conditions. However, the process of functionalization compromises other properties of the electrospun membrane due to the extent of sulfonation reaction that occurred. This study was carried out to determine the effects on microstructure and morphology of crosslinked electrospun polybenzoxazine (PBz) fibers by correlating the reaction kinetics using a specific reaction parameter with the degree of sulfonation (DS). The kinetics of sulfonation reaction for PBz fibers is an electrophilic-based, first-type substitution mechanism where only one sulfonic acid (-SO3H) group is attached to each of the repeating units in the aromatic structure of PBz under ordinary conditions. From a previous study, the rate of change of ion exchange capacity (IEC) was derived as a logarithmic correlation that increased rapidly for some time and became constant. This study employed the derived empirical relationship based on reaction kinetics to correlate the degree of sulfonation (DS) with IEC at varying reaction time. DS was calculated as 55%, 66% and 77%, for 3, 6 and 24 h, respectively. The maximum IEC of 2.71 with the corresponding DS of 100% was obtained theoretically but since sulfonation reaction kinetics at ordinary conditions proceeds at slower phase, it can only attain 86% DS with maximum IEC of 2.44 at a calculated time of 48 h. Sulfonation was confirmed by the functional groups present in the structural composition of PBz fibers using ATR-FTIR which were quantified based on the absorbance in the IR spectra showing an increased peak height with increased reaction time for the first 6 h. Morphological analyses using SEM images revealed an increase in fiber diameter with increased sulfonation time. In addition, the higher reaction time showed the effects of longer acid exposure which compromised the fibers' structural integrity with the presence of broken fibers and defects on fibers' surfaces after 24 h. The electrospun PBz fibers sulfonated for 6 h achieved the highest IEC value with DS of 66% which was enough to attain the balance of degree of sulfonation with electrochemical and morphological properties.

Ambient Humidity-Induced Phase Separation for Electrospun Fiber Morphology Engineering Toward Piezoelectric Self-Powered Sensing

Electrospun polymeric piezoelectric fibers have a considerable potential for shape-adaptive mechanical energy harvesting and self-powered sensing in biomedical, wearable, and industrial applications. However, their unsatisfactory piezoelectric performance remains an issue to be overcome. While strategies for increasing the crystallinity of electroactive β phases have thus far been the major focus in realizing enhanced piezoelectric performance, tailoring the fiber morphology can also be a promising alternative. Herein, a design strategy that combines the nonsolvent-induced phase separation of a polymer/solvent/water ternary system and electrospinning for fabricating piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE) fibers with surface porosity under ambient humidity is presented. Notably, electrospun P(VDF-TrFE) fibers with higher surface porosity outperform their smooth-surfaced counterparts with a higher β phase content in terms of output voltage and power generation. Theoretical and numerical studies also underpin the contribution of the structural porosity to the harvesting performance, which is attributable to local stress concentration and reduced dielectric constant due to the air in the pores. This porous fiber design can broaden the application prospects of shape-adaptive energy harvesting and self-powered sensing based on piezoelectric polymer fibers with enhanced voltage and power performance, as successfully demonstrated in this work by developing a communication system based on self-powered motion sensing.

Fabrication of Electrospun Xylan-g-PMMA/TiO2 Nanofibers and Photocatalytic Degradation of Methylene Blue.

Herein, xylan-g-PMMA was synthesized by grafting poly(methyl methacrylate) (PMMA) onto xylan and characterized by FT-IR and HSQC NMR spectroscopies, and the xylan-g-PMMA/TiO2 solution was used to electrospun nanofibers at the voltage of 15 Kv, which was the first time employing xylan to electrospun nanofibers. Moreover, the electrospinning operating parameters were optimized by assessing the electrospinning process and the morphology of electrospun fibers, as follows: the mixed solvent of DMF and chloroform in a volume ratio of 5:1, an anhydroxylose unit (AXU)/MMA molar ratio lower than 1:2, the flow speed of 0.00565–0.02260 mL/min, and a receiving distance of 10–15 cm. Diameters of the electrospun fibers increased with increasing DMF content in the used solvent mixture, MMA dosage, and receiving distance. TiO2 nanoparticles were successfully dispersed in electrospun xylan-g-PMMA nanofibers and characterized by scanning electron microscopy, energy dispersive X-ray diffraction spectrum, and X-ray photoelectron spectroscopy, and their application for methylene blue (MB) degradation presented above 80% photocatalytic efficiency, showing the good potential in water treatment.

Sustainable lithium-ion battery separators derived from polyethylene oxide/lignocellulose coated electrospun P(VDF-TrFE) nanofibrous membranes

A novel Polyethylene oxide/lignocellulose (PEO/LIGC) coated dimpled electrospun P(VDF-TrFE) nanofibrous membranes were prepared and are employed as a separator for lithium-ion battery. ESEM images revealed the dimpled morphology of electrospun fibers and PEO/LIGC is located on the surface as well as in the space between the fibers. Results of tensile studies prove that PEO/LIGC coating improves the mechanical strength and elongation at break. The wettability of the membrane with liquid electrolyte was studied by contact angle analysis and the results indicate that both the membranes are readily wetted by the electrolyte. The electrolyte uptake of ecofriendly LIGC coated sample is ∼ 440%, which is 647% higher than that of commercial Celgard separator. PEO/LIGC coated membrane shows ∼ 86% porosity, which is 226% higher than that of the Celgard separator. Ionic conductivity studies show that dip coated P(VDF-TrFE) exhibits a conductivity 7. 04 × 10−3 S cm−1. A 2320 type coin cell (Li/Separator/LiFePO4) were fabricated using PEO/LIGC coated P(VDF-TrFE) and the fabricated cell is superior to that of a Celgard 2320 separator. Thus, the study reveals that the lignocellulose, a sustainable material helps to enhance the overall performance of the battery.

Preparation and Characterization of Electrospun Polylactic Acid (PLA) Fiber Loaded with Birch Bark Triterpene Extract for Wound Dressing

Drug-loaded electrospun fibers have attracted increasing attention as a promising wound dressing material due to their capability of preventing from infections and inflammation and maintaining an appropriate environment for wound healing. In this study, polylactic acid (PLA), which is widely used in wound management, was chosen as electrospinnable polymer. A triterpene extract (TE) from the outer bark of birch known for its anti-inflammatory, antiviral, antibacterial, and wound healing effects was chosen to produce TE-loaded PLA electrospun fibers for wound dressing. A binary solvent system of dichloromethane (DCM) and dimethyl sulfoxide (DMSO) was employed, and the ratio of the solvents was optimized for preparing smooth and uniform fibers. The morphology of TE-loaded PLA electrospun fibers was investigated by scanning electron microscopy (SEM). The entrapment of TE in PLA fibers was confirmed by confocal laser scanning microscopy (CLSM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to analyze the solid state of TE in PLA fibers. The release behavior of TE was assayed by a shaking flask method for a period of 96 h. The results revealed that TE-loaded electrospun PLA microfibers could be reliably prepared and are promising future candidates in wound therapy.

Investigation of Different Membrane Porosities on the Permeate Flux of Direct Contact Membrane Distillation

In the present study the surface morphology of electrospun fibers at different polystyrene (PS) solution concentration was studied by SEM imaging to determine the best PS solution concentration yielding continuous uniform beadles fibers. Contact angle measurements of the optimum fabricatedPS-18 membrane confirmed the super hydrophobic property of the membrane that exhibited a static water contact angle of 145o. Numerical investigation of the performance of PS-18 membrane at different membrane thicknesses and porosities on direct contact membrane distillation showed that increasing the membrane porosity increases the permeate flux considerably.

Electrospun nanofibers fromferrocene‐containingmultiblock copolymers prepared viaRAFTpolymerization withF127modified precursor

AbstractElectrospun nanofibers from copolymers composed of ferrocene side chains and PEO100‐PPO65‐PEO100(F127) were fabricated in chloroform andN,N–dimethyl formamide solutions (V/V = 95:5) at room temperature. Ferrocene‐containing multiblock copolymers (PFcMAn‐F127‐PFcMAn) were synthesized through reversible addition‐fragmentation chain transfer polymerization using s‐1‐dodecyl‐s''‐ (α, α'‐dimethyl‐α''‐acetic acid) trithiocarbonate (DDMAT) modified F127 with 2‐ (methacryloyloxy) ethyl ferrocencarboxylate (FcMA). The structures of as‐obtained chemicals were characterized by FTIR,1H NMR, and13C NMR. Additionally, the block copolymers molecular weight and polydispersity were measured using gel permeation chromatography. The electrochemical responsiveness of the polymers was investigated using cyclic voltammetry as well as the thermal stabilities of polymers and precursors were tested through DSC and TGA. The morphologies of electrospun fibers were observed through field emission scanning electronic spectroscopy and a fibrous diameter of 300–1100 nm was obtained. The results indicated that the suitable molecular weight of ferrocene ‐containing polymer would be processed in nanofibrous.

Effect on thermal stability of microstructure and morphology of thermally-modified electrospun fibers of polybenzoxazines (PBz) blended with sulfur copolymers (SDIB).

Simple modification by thermal treatment is the commonly used approach to enhance the performance of electrospun fibers. This was investigated in the thermal treatment of polybenzoxazine (PBz) fibers blended with sulfur copolymers (SDIB) to determine the effect of varying treatment conditions on the microstructure and morphology of PBz fibers with the effect of incorporating sulfur functional groups on resulting properties. Mechanical properties of PBz are greatly improved by thermally-induced ring-opening polymerization (ROP) of the oxazine ring. Blending with sulfur copolymers (SDIB) could have beneficial effects on endowed features on fibers but could also affect the resulting properties of SDIB-blended PBz fibers during crosslinking reactions. Fiber mats were fabricated by electrospinning of PBz (10 wt%) blended with SDIB (10 wt%). Physical modification with varying conditions of sequential thermal treatment were evaluated and compared to the conditions applied on pristine PBz fibers. Changes in morphology and microstructure of fibers after modification were analyzed through scanning electron microscopy (SEM) while elemental compositions were identified after varying the conditions of thermal treatment. Adjustment of treatment conditions using two-step temperature sequential thermal treatment with higher temperatures of 160 °C and 240 °C showed significant changes in microstructure and morphology of fibers. Lower temperatures of 120 °C and 160 °C exhibited microstructure and morphology of fibers which affected the fiber diameter and fiber networks. Cross-sectional SEM images also confirmed the adversed effect of high-temperature treatment conditions on fibrous structures while low-temperature treatment retained the fibrous structures with more compact and stiff fiber networks. SDIB-blended PBz fibers were also evaluated by TGA and DSC to correlate the changes in structure and morphology with the thermal stability and integrity of blended SDIB/PBz fibers as compared to pristine PBz with the effect of change in treatment conditions. Fiber strength indicated slower weight loss for blended fibers and higher onset temperature of degradation which resulted in more thermally stable fibers.

Surfactant location and internal phase volume fraction dictate emulsion electrospun fiber morphology and modulate drug release and cell response.

Emulsion electrospinning is a versatile technique used to create fibrous meshes for applications in drug delivery and tissue engineering. In this study, the effects of surfactant and increasing internal phase volume fraction on emulsion electrospun fiber morphology were investigated. The fiber diameter, surface topography, internal architecture, mesh hydrophobicity, and fiber volume fraction were all characterized and the resulting effects on model drug release and cell response were determined. Surfactant relocation to the fiber surface resulted in alterations to fiber surface topography and internal morphology, increased rate of water adsorption into the mesh, and reduced burst effects of drug release. Increasing the internal phase volume fraction within the emulsion resulted in minimal change to fiber diameter, surface morphology, fiber volume fraction, and rate of water adsorption illustrating the ability to increase drug loading without affecting fiber properties. Lastly, all meshes promoted cell adhesion and good viability with a trend of increased MTT absorbance from cells on the surfactant and emulsion fibers possibly suggesting that an increase in surface area via smaller fiber diameter and fiber volume fraction increases metabolic activity. Overall, these studies indicate that fiber morphology and mesh hydrophobicity can be tuned by controlling surfactant location within fibers and internal phase volume fraction. Modulating fiber properties within the emulsion electrospun mesh is important to achieve controlled drug release and cell response for tissue engineering applications.

TUNING SURFACE ROUGHNESS OF ELECTROSPUN POLY CAPROLACTONE FIBRES BY SINGLE SOLVENT ELECTROSPINNING SYSTEM

Secondary surface texture or surface roughness is having a powerful impact on morphological variety and magnifies the application areas of electrospun fibres. This paper for the first time assesses the formation of varying degrees of surface pores on electrospun poly caprolactone (PCL) fibres by using a single solvent system. PCL solutions were prepared by dissolving PCL granules in dichloromethane (DCM) at the concentration of 5, 10, 15 and 20% (w/v), before being subjected to the electrospinning process at lower kV values of 5, 10 and 15, respectively. The morphology of electrospun fibres was characterised by field emission scanning electron microscope (FESEM). The resultant PCL fibres showed a highly porous surface was formed at lower PCL concentration. The surface roughness of PCL fibres was increased gradually with the increment of PCL concentration. The formation of porous surface was mainly due to the fast phase separation process while pore size and pore size distribution was found to depend on the blend composition.

Encapsulation of tangeretin in PVA/PAA crosslinking electrospun fibers by emulsion-electrospinning: Morphology characterization, slow-release, and antioxidant activity assessment

In this work, water-resistant poly (vinyl alcohol) (PVA)/poly (acrylic acid) (PAA) electrospun fibers encapsulating tangeretin (Tan) were fabricated by emulsion-electrospinning. To optimize the electrospinning condition, the size and morphology of electrospun fibers were characterized by dynamic light scattering (DLS), optical light microscope, fluorescence microscopy, and scanning electron microscopy (SEM), respectively. The optimized initial concentration of PVA/PAA was 10% (w/w) with a mass ratio of 3:7. The time and temperature of optimized thermal crosslinking treatment were 2 h and 145 °C, respectively. The results of XRD and SEM showed that the Tan was successfully incorporated into smooth PVA/PAA electrospun fibers and those fibers possessed nano-diameter size and high porosity. The encapsulation of Tan had no significant impact on the antioxidant activity of PVA/PAA/Tan crosslinking electrospun fibers. The in vitro release test showed the PVA/PAA/Tan crosslinking electrospun fibers achieved durable release profiles and lower burst release rates than that from the pure Tan emulsion. Based on these results, it is concluded that PVA/PAA/Tan crosslinking electrospun fibers prepared by emulsion-electrospinning serve as a promising technique in the fields of water-insoluble drug delivery and slow-release.

Feature extraction on Mueller matrix data for detecting nonporous electrospun fibers based on mutual information

The surface morphology of electrospun fibers largely determines their application scenarios. Conventional scanning electron microscopy is usually used to observe the microstructure of polymer electrospun fibers, which is time consuming and will cause damage to the samples. In this paper, we use backscattering Mueller polarimetry to classify the microstructural features of materials by statistical learning methods. Before feeding the Mueller matrix (MM) data into the classifier, we use a two-stage feature extraction method to find out representative polarization parameters. First, we filter out the irrelevant MM elements according to their characteristic powers measured by mutual information. Then we use Correlation Explanation (CorEx) method to group interdependent elements and extract parameters that represent their relationships in each group. The extracted parameters are evaluated by the random forest classifier in a wrapper forward feature selection way and the results show the effectiveness in classification performance, which also shows the possibility to detect nonporous electrospun fibers automatically in real time.

Alignment‐Improved and Diameter‐Reduced Electrospun Polymer Fibers via the Hot‐Stretching Process

AbstractElectrospinning is one of the most facile and versatile techniques to prepare polymer fibers ranging from micrometers to nanometers. Although several parameters can be tuned to control the sizes and morphologies of electrospun fibers, many obstacles are still encountered as the target sizes of the fibers are getting smaller; for example, the sizes of the fibers can be effectively reduced by lowering the polymer solution concentrations but beaded or beads‐on‐string structures are usually formed. To overcome such obstacles, here a simple technique to prepare alignment‐improved and diameter‐reduced fibers without bead formation by hot‐stretching electrospun fibers at temperatures higher than the glass transition temperatures of the polymers is developed. Polystyrene and poly(methyl methacrylate) are both used in this work as model materials. The relationship between the draw ratio and diameter of the fibers is quantitatively analyzed, demonstrating the control of the fiber diameters. Moreover, higher degrees of alignment improvement at the middle part of the fibers than those at the end part is observed, which results in lower water contact angles at the middle part of the fibers. This work provides a useful post‐treatment technique to control the sizes and orientations of electrospun polymer fibers.

Electrospinning technique for the fabrication of poly(styrene-co-methyl methacrylate) nanofibers and the effect of fiber diameter on UV–Visible absorption and thermal properties

Nanofibers are gaining much importance in research field owing to its versatile applications and unique properties. Eventhough different methods are there to fabricate nanofibers; electrospinning is of great interest due to its added advantages in terms of cost effectiveness and wide applicability. Among different materials electrospun polymers are more preferred because of no post-processing requisites. The major challenge associated with electrospinning is to optimize the parameters determining the fineness of surface morphology of electrospun fibers. In the present study an attempt is made to investigate the effect of solution parameters such as concentration of the polymer solution, nature and ratio of solvent type and the processing parameters like applied voltage on the fineness of fiber surface morphology of copolymer poly(styrene-co-methyl methacrylate) fibers. The effect of fiber diameter on thermal degradation is monitored. The concentration studies were done by varying the concentration from 3% (w/v) to 20% (w/v) and for solvent studies varying proportions of THF and DMF were chosen. Voltage studies were carried out by varying the applied voltage from 15 kV to 25 kV. The characterization techniques include SEM, TGA UV–Visible Spectroscopy and FTIR analyses. The results showed that by adjusting the applied voltage, concentration of the polymer and solvent ratio, a good control over the fineness of surface morphology can be accomplished. From the TGA analysis it is found the degradation property of nanofibers varied as a function of fiber diameter.

The thermo-optic relevance of Ho3+ in fluoride microcrystals embedded in electrospun fibers.

Na(Y1−x−yHoxYby)F4/PAN (NYF-HY/PAN) composite fibers were synthesized using an electrospinning method, and the sub-micron crystals embedded in the fibers had complete hexagonal crystal structures. Under 977 nm laser excitation, strong green and red up-conversion (UC) emission that originated from flexible fibers were due to the radiative transitions (5F4, 5S2) → 5I8 and 5F5 → 5I8 of Ho3+, respectively. The effective green fluorescence emission (539 and 548 nm) can be applied to micro-domain non-contact temperature measurements, realizing rapid and dynamic temperature acquisition in a complex environment without destroying the temperature field. In the temperature range of 313–393 K, the absolute and relative sensitivity of the fibers are 0.00373 K−1 and 0.723% K−1, respectively, which indicates that the NYF-HY/PAN composite fibers have good thermal sensitivity. Composite fibers in which crystallites are embedded have superior properties, with great stability, high sensitivity, and excellent flexibility, providing a reliable reference for developing temperature-sensing materials for the biomedical field.