Fiber Surface Research Articles

Repercussion of fiber content on the mechanical, thermal, and thermomechanical properties of natural fibers reinforced thermoplastic composites for automotive application

Natural fibers are becoming very popular as a reinforcement in composite materials owing to their benefits, such as low-price, lightweight, availability, and environmental friendliness. In this study, abaca fiber-reinforced polypropylene (PP) and high-density polyethylene (HDPE) composites were created with the help of the injection molding method. Prior to composite fabrication, abaca fibers were chemically treated with a 5 wt% caustic soda (NaOH) solution to improve the bonding between the abaca fibers and the matrix and to enhance their properties. Scanning electron microscopy (SEM) was utilized to assess the fiber surface microstructures before as well as after the chemical treatment, along with the fractured surfaces of tensile specimens. The mechanical properties, such as tensile, bending, and impact strength, of abaca/PP and abaca/HDPE composites were evaluated and compared. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods were utilized to investigate the thermal behavior of composites. Also, the dynamic mechanical analysis (DMA) method was utilized to explore the thermomechanical properties of the fabricated composites. The outcomes of the experimental findings showed that abaca/PP composite with 10 and 20 wt% fibers is the best choice of material to be used in the automobile industry.

Simulation analysis of a photonic crystal fiber refractive index sensor based on a double-layer film structure and surface plasmon resonance technology

A photonic crystal fiber surface plasmon resonance sensor based on a double-layer membrane structure is designed and analyzed. In the simple sensing structure with only one air hole size, TiO2 and Au layers with specific thicknesses are sequentially coated on the optical fiber to form a double-layer structure. The sensing characteristics of the double-layer membrane structure are studied by the finite element method. Compared to the single-layer membrane structure, the double-layer membrane sensor has significant sensing properties such as a better wavelength sensitivity and a smaller full width at half maximum in the loss spectrum. In the refractive index range between 1.37 and 1.43, the maximum wavelength sensitivity and average wavelength sensitivity of the sensor are 19,900 nm/RIU and 7417 nm/RIU, respectively, and the resolution can be up to 5.03×10−6RIU. The proposed photonic crystal fiber optic sensor achieves high performance with a simpler sensing structure than previous photonic crystal fiber optic sensors, and eliminates the step of polishing, which will greatly reduce the difficulty of actual fabrication and the error due to uneven polishing. The results show that the photonic crystal fiber optic sensor with a double-layer membrane structure has excellent performance. Due to its high sensitivity and resolution, it has great potential for applications in environmental monitoring, biosensing and chemical sensing.

Distribution of xylan linked glucuronic acid labelled by molecularly imprinted polymers on pulp fiber surface

Efficiently utilization of plant resources is heavily restricted by the resistance of lignocellulose in plant cells, which is related to the interlinkages of lignocellulose components. Hemicellulose in plant cell wall is bound to cellulose by hydrogen bond and linked with lignin in lignin-carbohydrate complex (LCC). In the xylan chain of hemicellulose, glucuronic acid (GA) is a typical side-group, which provides clues for us to label and locate hemicellulose. The way to label GA on the surface of pulp fibers obtained from pulping process is benefit to explore the deconstruction of lignocellulose. Herein, a new visualization method, fluorescence modified molecularly imprinted polymers (MIP) were applied to recognize and locate GA on the pulp fiber surface. The method combining fluorescence imaging and integrated 3D fiber structure verified the feasibility of the MIP for specific GA recognition. The results showed that xylan (represented by GA) was closely attached to lignin, distributed along the inner wall of pulp fiber cells, and gradually taken off from the inside edge of fiber cells with the deconstruction of lignocellulose. This research provided a basis to develop visualization bioimaging technology to identify biomass components.

Polydopamine-induced biomimetic mineralization strategy to generate hydroxyapatite for the preparation of carbon fiber composites with excellent mechanical properties

Living organisms have developed a miraculous biomineralization strategy to form multistage organic-inorganic composites through the orderly assembly of hard/soft substances, achieving mechanical enhancement of materials from the nanoscale to the macroscale. Inspired by biominerals, this study used polydopamine (PDA) coating as a template to induce the growth of hydroxyapatite (HAP) on the surface of carbon fibers (CFs) for enhancing the interfacial properties of the CF/epoxy resin composites. This polydopamine-assisted hydroxyapatite formation (pHAF) biomimetic mineralization strategy constructs soft/hard ordered structure on the CF surface, which not only improves the chemical reaction activity of the CFs but also increases the fiber surface roughness. This, in turn, enhances the interaction and loading delivery among the fibers and the matrix. Compared to the untreated carbon fiber/epoxy resin (CF/EP) composites, the prepared composites showed a substantial enhancement in interlaminar shear strength (ILSS), flexural strength, and interfacial shear strength (IFSS), with improvements of 45.2 %, 46.9 %, and 60.5 %, respectively. This can be attributed to the HAP nanolayers increasing the adhesion and mechanical interlocking with the CFs to the matrix. This study provides an interface modification method of biomimetic mineralization for the preparation of high strength CF composites.

Effect of surfactants on enzymatic hydrolysis of PET

Enzyme is difficult to adsorb on the surface of high-crystallinity poly(ethylene terephthalate) fibers (PET，crystallinity of 48.56 %) due to the high hydrophobicity of PET fibers. Surfactants can effectively reduce the PET/water interface tension and improve the adsorption of enzyme on PET fibers, increasing the degradation of PET fibers promoted by enzyme. In this paper, different nonionic surfactants (Triton X-100, Triton X-114, Triton X-405, PEG 200, PEG 400, PEG 600, Tween 20, Tween 80) were selected to investigate the effect of surfactant on the degradation of PET fibers by enzyme. It was found that the addition of Triton X-405 can improve the concentration of degradation products. However, other surfactants selected in this paper, such as Tween-80 caused the decrease of the degradation yields. The results indicated that the structure of surfactant plays a very important roll on the degradation of PET catalyzed by enzyme. This is probably due to the transformation of enzyme conformation induced by surfactant, and affects on the activity of enzyme. The hydrophilic surface is beneficial to the adsorption of enzyme onto the surface of PET fibers, and further improve the degradation of PET fibers.

Electroless plating of copper on carbon fiber surfaces and corresponding mechanism

Abstract Traditional methods for surface pretreatment of carbon fibers often rely on the use of precious metals like palladium and silver as activators to enhance surface reactivity through redox reactions, achieving metallization. However, such approaches are costly and economically inefficient. This study employed a cost-effective copper (Cu) – nickel (Ni) colloid mixture as an activator and investigated its effectiveness in enhancing surface reactivity. Meanwhile, it examined the influence of various parameters, such as pH value, reducing agent (formaldehyde (HCHO) concentration, temperature, and deposition duration, on the morphology and structure of copper-electrodeposited carbon fibers. To characterize the treated samples, scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS) were adopted, shedding light on the mechanism underlying copper electrodeposition on the carbon fiber surface. The results indicate that Cu-Ni colloid mixture activation exhibits significant improvements. The optimal conditions for uniform and smooth copper electrodeposition on the carbon fiber surface identified as follows: a pH value of 13.5, a HCHO concentration of 15 mL/L, a temperature of 50°C, and a deposition duration of 5 min. Consequently, these results represent a cost-effective alternative to traditional precious metal-based activation methods, with promising applications in surface pretreatment for carbon fibers.

Development and Evaluation of a Novel Fish-Derived Protein Peptide Conditioner Formulated with Pneumatophorus japonicus Heads Peptides

Given the unique advantage of hair conditioners formulated with marine-derived proteins and their hydrolysates in terms of green, effective, sustainable, and environmentally friendly. This study presents a novel fish-derived protein peptide-based hair conditioner that featuring Pneumatophorus japonicus heads peptides (PHP). Results demonstrate that the PHP conditioner exhibits favorable sensory properties, improves the surface morphology and structure of damaged hair, reduce the degree of fragmentation and roughness, improve the gloss and make hair smoother. PHP penetrates into the hair shaft, interacting with hair fiber keratin to enhance the integrity and stability of the α-conformation of hair keratin. Furthermore, the PHP conditioner treatment increased total amino acid content by 4.98% and hydrophobic amino acid content by 2.67%, approaching the levels observed in virgin hair. Therefore, the PHP conditioner effectively permeates the surface and interior of hair fibers, filling voids and ameliorating changes in both the microstructural and compositional aspects of the hair. These improvements surpass those observed with a commercially available wheat protein conditioner. Overall, the PHP conditioner effectively repairs damaged hair, offering a new strategy for the development of innovative natural hair care products.

Highly sensitive near-field leakage-enhanced optical fiber SPR sensor based on gold nanoarrays modulation

A novel near-field leakage-enhanced optical fiber surface plasmon resonance (NLF-SPR) sensor based on the synergistic sensitization of cuboid gold nanoarrays and WSe2 film is proposed for the first time to our knowledge. The sensor is composed of a side-polished multimode fiber, a continuous gold film, a continuous tungsten selenide (WSe2) film, and well-arranged cuboid gold nanoarrays. The sensor leverages the high carrier mobility characteristic of the WSe2 film, the near-field leakage enhancement arising from the nanoarrays structure, and the localized electric field enhancement property introduced by nanotips to enhance the refractive index sensitivity. In order to optimize the spectral characteristic, the modulation of electric field distribution and spectral characteristic by the structural parameters of gold nanoarrays is investigated through three-dimensional (3D) finite element simulation. Results show that in the refractive index range of 1.3332–1.3432 refractive index unit (RIU), the average sensitivity of the NLF-SPR sensor can reach up to 10108 nm/RIU, and the highest sensitivity can reach up to 14692.46 nm/RIU. The average sensitivity and the highest sensitivity are 1.87 times and 2.56 times higher, respectively, than those of the side-polished fiber SPR sensor with a monolayer gold film. Furthermore, the experimental results demonstrate that the near-field leakage enhancement introduced by gold nanoarrays improves the performance of the fiber SPR sensor, resulting in a 49.3 % increment in sensitivity. The experimental results are in agreement with the trend of the simulation results. Even better performance improvements have been achieved compared to existing methods and a more flexible approach to performance tuning is provided. With the maturity and development of various nanoarray processing techniques such as focused ion beam, electron beam lithography, and nanoimprint lithography, the proposed NLF-SPR sensor has the potential to be fabricated on a large scale and is expected to be widely employed in biomedical, clinical applications, and other fields.

Study on the effect of heat treatment on the structure, mechanical and electrical properties of alumina fiber insulation

In this paper, the heat treatment of alumina fiber was studied. The infiltration agent on the fiber surface was removed after heat treatment at 450 °C for 6 h. TG-DSC, scanning electron microscope, x-ray diffraction, Fourier infrared spectrometer, energy dispersive spectrometer, and patterning were used to analyze the thermal weight loss, fiber surface morphology, crystal structure, and composition of alumina fibers. The results show that the aluminum oxide fiber has excellent temperature resistance and does not undergo crystal phase transformation during thermal weight loss. After heat treatment, the fiber surface infiltration agent ablates and dissolves from the fiber surface, and the internal crystal structure of the fiber remains stable. The tensile testing machine was utilized to test the breaking strength of alumina fiber. The fiber still maintained high strength after heat treatment, and the retention rate of breaking strength was greater than 74%. ZC-90G high insulation resistance measuring instrument and WDY-Ⅱ automatic voltage tester were utilized to analyze the insulation resistivity and breakdown strength of alumina fiber before and after heat treatment. The results show that heat treatment can effectively improve the insulation performance and breakdown strength of alumina fiber.

Ultrasensitive optical fiber SPR sensor enhanced by Au-NPs-film modified with functionalized CQDs for label-free detecting cobalt (II) ion

BackgroundCobalt, an essential trace element, is vital for maintaining human nervous system function, aiding in DNA synthesis, and contributing to red blood cell production. It is helpful for disease diagnosis and treatment plan evaluation by precisely monitoring its concentration changes in the human body. Despite extensive efforts made, due to its ultra-low concentration, the current limit of detection (LOD) as reported is still inadequate and cannot be satisfied with the precise clinical applications. Therefore, it is crucial to develop novel label-free sensors with high sensitivity and excellent selectivity for detecting trace amounts of Co2+. ResultsHere, an ultrasensitive optical fiber SPR sensor was designed and fabricated for label-free detection of Co2+ with ultra-low concentration. It is achieved by modifying the carboxyl-functionalized CQDs on the AuNPs/Au film-coated hetero-core fiber, which can specifically capture the Co2+, leading to changes in the fiber's surface refractive index (RI) and subsequent SPR wavelength shifts in the transmission spectrum. Both the Au film and AuNPs on the fiber are modified with CQDs, leveraging their large surface area to enhance the number of active sites and probes. The sensor exhibits an ultra-high sensitivity of approximately 6.67 × 1019 nm/M, and the LOD is obtained as low as 5.36 × 10−20 M which is several orders of magnitude lower compared to other conventional methods. It is also experimentally demonstrated that the sensor possesses excellent specificity, stability, and repeatability, which may be adapted for detecting real clinical samples. SignificanceThe CQDs-functionalized optical fiber SPR sensor exhibits substantial potential for precisely detecting Co2+ of trace amounts, which is especially vital for scarce clinical samples. Additionally, the sensing platform with sample sensor fabrication and measurement configuration introduces a novel, highly sensitive approach to biochemical analysis, particularly adapting for applications involving the detection of trace targets, which could also be employed to detect various biochemical targets by facile modification of CQDs with specific groups or biomolecules.

Construction of Hierarchical Black TiO2/Carbon Fiber: Enhanced Photocatalytic Activity Based on Schottky Heterojunctions.

Photocatalytic antimicrobials, as emerging advanced oxidative antimicrobial materials, have the advantages of low price and long-lasting antimicrobial properties. Nevertheless, with catalysts increasingly trending toward nanoscale dimensions, the environmental challenge of catalyst recycling becomes more pronounced. In this paper, we propose utilizing one-dimensional carbon fiber as a substrate, employing the nucleating agent method to induce Titanium dioxide (TiO2) growth on the fiber surface. Furthermore, the material's band gap underwent modification through hydrogen calcination, thus resulting in the attainment of hierarchical black TiO2/carbon fiber composites with visible light-driven capabilities. The characterization of the materials was conducted via scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results revealed that when the black hydrogenated TiO2 was composited with carbon fiber, the Schottky heterojunction was formed, and thus effectively improved the photocatalytic effect of the composites. Notably, the degradation rate of methylene blue achieved 96.25% within 150 min when utilizing black TiO2/carbon fiber composites, while the inactivation rate of Escherichia coli (E. coli) reached 97.58% within 0.5 h and attained complete inactivation within 60 min.

Saturable absorption properties of mixed lead-tin halide perovskites and their application in near-infrared ultrafast lasers

Mixed lead–tin halide perovskites, as highly sensitive materials in the near-infrared region, hold significant potential for optoelectronic device applications. Here, mixed lead–tin halide perovskite saturable absorbers (SAs) have been developed by coupling with the side-polished surfaces of the single-mode fibers and excellent saturable absorption effects of the mixed lead–tin halide perovskite SAs have been demonstrated in the near-infrared region. By constructing the in-gap site assisted carrier transfer mode, the saturation absorption process of the mixed lead–tin halide perovskite SAs can be well explained, in which defects as in-gap sites can help the photon-generated carriers transfer into the conduction band and promote the Pauli-blocking-induced absorption bleaching in the SA. Moreover, ytterbium-doped fiber lasers based on perovskite SAs have been fabricated, and mode-locked operations at 1040 nm are achieved using the mixed lead–tin halide perovskite SA, generating ultra-short pulses with a pulse width of 683 fs, 3 dB bandwidth of 4.88 nm, signal-to-noise ratio exceeding 49.74 dB, and a repetition rate of 3.74 MHz. Our findings demonstrate that the mixed lead–tin halide perovskite SAs have excellent optical modulation capability and promising applications in the field of ultrafast photonics.

Surface properties of activated carbon fibers obtained from polyacrylonitrile and methyl acrylate: Experimental and simulation studies for lead and acid blue 25 dye adsorption from water

Activated carbon fibers were prepared using a methyl acrylate/polyacrylonitrile (MA/PAN) system and H3PO4 activation. These fibers were assessed to adsorb AB25 and Pb2+ from aqueous solutions, and DFT calculations were carried out to determine the main surface interactions that caused the removal of both pollutants. The results showed that AB25 and Pb2+ adsorption on these activated carbon fibers was endothermic, with maximum experimental adsorption capacities of 0.012 − 0.023 and 0.248 − 0.306 mmol/g at 20 – 40 °C. Pb2+ adsorption properties of these fibers outperformed those of other carbonaceous materials utilized in the depollution of metallic cations, whereas their removal effectiveness was less competitive to separate AB25 dye molecules. A double-site monolayer model was applied to correlate the experimental Pb2+ isotherms, while AB25 adsorption on activated carbon fibers was simulated using a one-site multilayer model. Oxygenated acidic (i.e., carboxylic and phenolic) and phosphate-carbon functional groups were the main binding sites to adsorb these pollutants. The adsorption energies of the tested systems, the identification of the most feasible binding positions of the tested adsorbates on the activated carbon fiber surface, and the role of hydrogen bonding in the corresponding adsorption mechanisms were discussed using DFT calculations. These results contribute to the valorization and application of engineered materials such as activated carbon fibers for water depollution.

A Study on the Surface Oxidation Pretreatment and Nickel Plating Mechanism of Carbon Fiber

This study explores the effects of various temperatures on the surface modification of carbon fibers, as well as the effect of differing voltages and currents on the morphology, deposition rate, and thickness of the Ni plating layers. Post-treatment characterization of the samples was conducted utilizing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods, thus facilitating a discussion on the mechanism of Ni plating. The findings demonstrate that at a temperature of 500 °C, the carbon fiber surface exhibits the highest concentration of functional groups, including hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O), resulting in the most efficacious modification. Specifically, exceeding 500 °C leads to significant carbon fiber mass loss, compromising the reinforcement effect. Under a stable voltage of 7.5 V, the Ni-plated layer on the carbon fibers appear smooth, fine, uniform, and complete. Conversely, at a voltage of 15 V, the instantaneous high voltage induces the continuous growth of Ni2+ ions along a singular deposition point, forming a spherical Ni-plated layer. In addition, a current of 0.6 A yields a comparatively uniform and dense carbon fiber coating. Nickel-plated layers on a carbon fiber surface with different morphologies have certain innovative significance for the structural design of composite reinforcements.

Recent advances to engineer tough basalt fiber reinforced composites: A review

AbstractBasalt fibers, known as “green materials without pollution in the 21st century”, have gained widespread attention due to its good mechanical properties. Basalt fiber‐based composites have applications in various fields such as construction, transportation, energy, and protection. However, as an inorganic fiber material, basalt fiber is hard and brittle and prone to catastrophic failure, reducing the safety of the material. Therefore, it is important to strengthen the toughness of basalt fiber‐based composites. This paper reviews the contributions made by researchers in recent years to enhance the toughness of basalt fiber reinforced composites. It mainly focuses on four aspects: physical and chemical modification of fibers surface, mixed application of multiple fibers, different textile and 3D printing technology, and design of biomimetic structures. Through these methods, the toughness of basalt fiber‐reinforced composite materials was increased by 10%–90%. In today's advocacy for green industrial development, the research and application of basalt fibers are very important for advancing the process of green development. These contributions can promote the application of basalt fiber in engineering fields.Highlights Basalt fiber is a green material without pollution. Basalt fiber reinforced composites is the key material for engineering field. Strengthening interfacial adhesion can significantly improve the toughness of composites. Basalt fibers can serve as an alternative to glass fibers in composite materials. The hybridization of basalt fibers with soft fibers can effectively enhance the toughness of composites.

Functionalising kapok fibre with lignin to enhance the structural and thermal performance of vacuum insulation panels

Kapok fibre has the advantage of low density, low porosity and low thermal conductivity, which make it an excellent substitute for fumed silica and environmentally-unfriendly synthetic polymers as core material of vacuum insulation panels (VIP). However, kapok fibre is hydrophobic, consequently, kapok fibre core materials made by conventional wet forming with weakly-bound fibres and large voids that shorten their service life. Lignin is a natural and sustainable material that has good hydrophilicity and small particle size to form nano-porous networks. Therefore, we herein present the incorporation of lignin in kapok fibre to generate a composite core material with hierarchical porous structure. Lignin functionalises the kapok fibre surface to make it hydrophilic and dispersible in water. Simultaneously, lignin enhances the mechanical properties and service life of core material by transforming its internal microstructure. The effective thermal conductivity of prepared VIP is below 6.00 mW/(m∙K), and after 28 days of accelerated ageing test without desiccant or getter, the effective thermal conductivity increases less than 5.00 mW/(m∙K). Interestingly, the addition of lignin also reduces radiative heat transfer in the VIP. So, lignin addition enables high-performance VIP to be produced. Moreover, as a natural material, kapok fibre is low-cost, environmentally-friendly, sustainable, and energy-efficient.

Characterization and mechanism analysis of interfacial shear strength between individual aramid fiber and epoxy by oxygen plasma treatment at elevated temperatures: Experiment and simulation

The weak adhesion between aramid fibers Ⅲ and the resin matrix, due to its smooth surface and high inertness of the fibers. This property restricts the mechanical properties of the composites in high temperatures environments. This work describes the treatment of aramid fibers Ⅲ with oxygen plasma to introduce reactive oxygen-containing functional groups onto fiber surface. The analysis focused on the impact of interfacial friction and interfacial wettability on the transfer of load across composites at various temperatures. According to the X-ray photoelectron spectroscopy (XPS) analysis, the fiber surface showed an increase in the number of active groups after plasma treatment. In addition, two new oxygen-containing functional groups -C-O- and -O-CO appeared. The use of Scanning Electron Microscopy (SEM) and atomic Force Microscopy (AFM) showed that the plasma treatment has an etching effect on the fiber surface and increases the roughness of the fiber surface. Furthermore, after plasma treatment, the fibers adhered to the resin matrix through hydrogen bonding and π-π bonding. The utilization of this technique led to a significant enhancement in the interfacial properties of monofilament composites across various temperature ranges. The IFSS of plasma-treated aramid fiber Ⅲ/EP exhibited increases of 38 % at the test temperature of 25℃. Surprisingly, the IFSS of plasma-treated aramid fiber III/EP exhibited a significant increase of 52 % at the test temperature of 120℃. In this paper, COMSOL software was utilized to simulate the IFSS before and after plasma treatment at different temperatures. Mechanistically explains the effect of temperature on the interfacial mechanical properties of composites.

Preparation of surfactant‐assisted polycaprolactone/κ‐carrageenan nanofibres

AbstractThe objective of this work was to fabricate nanofibres composed of polycaprolactone (PCL) and κ‐carrageenan (kC) by employing an anionic surfactant, sodium bis(2‐ethylhexyl) sulfosuccinate (AOT). This study examined the role of the surfactant in PCL/kC/AOT (hybrid) nanofibre preparation using SEM, AFM, Fourier transform infrared spectroscopy, XRD and DSC. The wettability and water uptake percentage of the nanofibres were investigated. An antimicrobial study was conducted against bacterial strains using a colony‐counting assay, and changes in bacterial morphology were monitored using TEM. The results demonstrated that the hybrid nanofibres had a uniform and smooth structure, which might be attributed to the improved compatibility between polymers in the presence of the surfactant. The incorporation of AOT in the matrix resulted in a reduction in the mean fibre diameter and surface roughness. The hybrid nanofibres increased water absorbency is evidence of their high hydrophilicity, which can be explained by the simultaneous impact of kC and AOT. The hybrid nanofibres exhibited effective activity against Staphylococcus aureus and Escherichia coli. © 2024 Society of Chemical Industry.

Effect of incubation conditions of cellulase hydrolysis on mechanical pulp fibre morphology

The mechanical pulp industry is diversifying through the manufacture of high-value paper products, such as microfibrillated cellulose. However, the development of fibre quality is still energy-intensive. Enzymatic hydrolysis is hypothesized to promote fibre cutting, greater fibrillation, and reduce refining energy costs. Despite potential benefits, there is little understanding of the mechanisms behind fibre development during enzymatic hydrolysis of mechanical pulp. This work investigates how incubation pH and temperature during enzymatic hydrolysis impact the refining of mechanical pulp short fibres. Incubation with endoglucanase at pH 5 and 60 °C increased fibre cutting by approximately 20 %. Fibrillation was negatively affected at this condition, resulting in increased slim fines formation with refining. Incubation at pH 8 and 80 °C promoted >15 % reduction in fibre length, despite such conditions being associated with low enzyme activity. The pH variation modified the sedimentation height of the fibres and the conductivity of suspensions, indicating a change in fibre surface charge. Fibre morphology changes were induced by enzyme hydrolysis conducted at conditions representative of the full range of pH and temperature observed in mechanical pulp mills.

Fabrication of SNAP structures by wire heating.

Surface Nanoscale Axial Photonics (SNAP) is a promising technological platform for creating novel optical devices such as compact high-Q tunable delay lines, signal processors, and optical comb generators. For this purpose, the development of simple and reliable methods for the accurate introduction of a nanometer-scale variation of the optical fiber surface is desirable. Here, we present an easy-to-implement technique for the introduction of nanoscale variations of the effective optical fiber radius by annealing with a heated metal wire. Using the proposed method, we introduce modifications of the fiber effective radius with accuracy better than 0.1 nm without post-processing, making the proposed approach the simplest alternative to the previously developed SNAP fabrication techniques.