Colloidal Fibers Research Articles

The Effect of Aqueous Extract of Fenugreek Plant on the Pancreas in Rabbits Induced with Diabetes and the Histological Changes Occurring in Them

The study aimed to induce alloxan-induced diabetes in local white rabbits, study its effect on the pancreas, treat them with aqueous extract of fenugreek at a concentration of 200 mg/kg orally, and observe the histological changes. To complete the study 20 white rabbits were taken and divided into three groups; 1st group is the control group and this group was dosed with distilled water. 2nd group was treated with Alloxan and was injected intraperitoneally at a dose of 175 mg/kg. 3rd group is the group that was treated with the aqueous extract of fenugreek at a concentration of 200 mg/kg for 30 days. After the end of the injection and dosing period after 30 days, the animals were killed and the pancreas was removed to perform histological techniques on them. its the group treated with alloxan was observed that the pancreas was composed of exocrine glandular lobules with enlarged secretory cells within the pancreatic acinus, with the presence of pale nuclei lacking pigment. Also, blood congestion of the blood vessels was found between the lobules of the gland and the pancreatic gland showed hyperplasia of its glandular epithelial cells with nuclei devoid of pigment due to the loss of the basal pigment in them. Blood congestion of the blood vessels appeared in the gland between the lobules, and dense colloidal fibers appeared in them and contained fibroblasts and phagocytic cells and the group treated with the aqueous extract of the fenugreek plant :The pancreatic parenchyma contained normal exocrine glandular secretion units, where the cytoplasm and nuclei of these cells were located in the form of regular axes, septations between the lobules of the pancreas surrounded by thick-walled arteries containing blood. and the islets of Lankerhans appeared between the yeast-secreting lobules of the pancreas. They contained endocrine cells of alpha and beta cells surrounded by blood sinusoids. The interstitial tissue between the lobules is composed of loose connective tissue containing colloidal fibers the pancreatic tissue contained the serous secretory vasculature of yeasts, which were uniform in shape, and between them were found blood vessels excessive with blood, where blood was found in a decomposed form in them, with the presence of small channels inside the lobules that transport yeasts.

Characterizing Phase Transitions of Microfibrillated Cellulose Induced by Anionic and Cationic Surfactants.

Rheological modifiers are used to tune rheology or induce phase transitions of products. Microfibrillated cellulose (MFC), a renewable material, has the potential to be used for rheological modification. However, the lack of studies on the evolution in rheological properties and structure during its phase transitions has prevented MFC from being added to consumer, fabric, and home care products. In this work, we characterize surface-oxidized MFC (OMFC), a negatively charged colloidal rod suspension. We measure the rheological properties and structure of OMFC during sol-gel phase transitions induced by either anionic or cationic surfactant using multiple particle tracking microrheology (MPT). MPT tracks the Brownian motion of fluorescent probe particles embedded in a sample, which is related to the sample's rheological properties. Using MPT, we measure that OMFC gelation evolution is dependent on the charge of the surfactant that induces the phase transition. OMFC gelation is gradual in anionic surfactant. In cationic surfactant, gelation is rapid followed by length scale-dependent colloidal fiber rearrangement. Initial OMFC concentration is directly related to how tightly associated the network is at the phase transition, with an increase in concentration resulting in a more tightly associated network with smaller pores. Bulk rheology measures that OMFC forms a stiffer structure but yields at lower strains in cationic surfactant than in anionic surfactant. This study characterizes the role of surfactant in inducing phase transitions, which can be used as a guide for designing future products.

Solvent-Induced Programable Wettability/Transparency Transition of Electrospun Colloidal Fibers with Embedded Polymer Nanospheres for Oil Adsorption and Plastic Remediation

Solvent-Induced Programable Wettability/Transparency Transition of Electrospun Colloidal Fibers with Embedded Polymer Nanospheres for Oil Adsorption and Plastic Remediation

Mechanistic understanding regarding the functionality of microcrystalline cellulose and powdered cellulose as pelletization aids in wet-extrusion/spheronization

Powdered cellulose (PC) and microcrystalline cellulose (MCC) show considerable different behavior during wet-extrusion and spheronization. While MCC is an appropriate pelletization aid, PC is not suitable. The differences were explained by either the “molecular-sponge” or the “crystallite-gel” hypothesis. To elucidate the differences in functionality, the effect of several polar solvents on liquid–solid interaction with PC and MCC was investigated. In addition, PC was homogenized via high pressure homogenization to reduce particle size without affecting the degree of polymerization. Mixer torque rheometry (MTR), laser diffraction and texture analysis were used to characterize the behavior of PC and MCC in wet pastes, suspensions and pellets. PC and MCC interacted differently with solvents like dimethyl sulfoxide, dimethylformamide and several glycols during MTR experiments. While PC mainly swells in appropriate solvents, MCC showed a particle size reduction, partly into colloidal dimensions. Solvents that induced liberation of colloidal fibers, also enabled a wet-extrusion/spheronization process. The quantity of colloidal cellulose only had minor effect on the resulting pellet quality. Also, the properties of the used solvent had only minor impact on the pellet size, shape and mechanical stability. PC contained small amounts of colloidal fibers after high pressure homogenization. With this pre-treated PC, wet-extrusion/spheronization process was also possible although the pellet quality is inferior to MCC pellets. Colloidal cellulose fibers have a major impact on the behavior of wet mass and on the feasibility for pellet production via wet-extrusion/spheronization. These insights provide new evidence for the “crystallite-gel” model.

Colloidal fibers and rings by cooperative assembly

Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins. While there are numerous computer studies, there are few experimental realizations due to a lack of means to produce such colloids with a well-controlled variable Janus balance. Here, we report a simple scalable method to precisely vary the Janus balance over a wide range and selectively functionalize one patch with DNA. We observe, via experiment and simulation, the dynamic formation of diverse superstructures: colloidal micelles, chains, or bilayers, depending on the Janus balance. Flexible dimer chains form through cooperative polymerization while trimer chains form by a two-stage process, first by cooperative polymerization into disordered aggregates followed by condensation into more ordered stiff trimer chains. Introducing substrate binding through depletion catalyzes dimer chains to form nonequilibrium rings that otherwise do not form.

Direct-writing Structure Color Patterns on the Electrospun Colloidal Fibers toward Wearable Materials

This study presents a direct-writing structure color patterns on electrospun colloidal fibers by inkjet printing. The colloidal fiber was obtained by electrospinning the aqueous mixture of colloidal particles of poly(styrene-methyl methacrylate-acrylic acid) and poly(vinyl alcohol). The pattern was obtained by directly inkjet printing water onto the electrospun colloidal fiber. The pattern formation was attributed to the morphological transition of the colloidal fiber from the fiber aggregation to latex aggregation and the corresponding color change due to the dissolution of poly(vinyl alcohol) by water. Interestingly, a clear and clean image was successfully obtained on the ethanol-treated colloidal fibers film in comparison to a confused and blur image onto the freshly-made film. It is because the treatment process can compact the fiber structure and lower the spreading/wetting behavior of ink on the fiber structure, contributing to the formation of high-quality pattern. Various letters or quick response code were flexibly designed and printed on to colloidal fibers. Furthermore, the pattern can be easily transferred onto flexible substrate, i.e., a flexible printed bracelet. This work will be of great significance for the development of novel wearable functional materials/devices based on electrospun colloidal fibers.

Colloidal fibers as structurant for worm-like micellar solutions

We investigate the rheological properties of a simplified version of a liquid detergent composed of an aqueous solution of the linear alkylbenzene sulphonate (LAS) surfactant, in which a small amount of fibers made of hydrogenated castor oil (HCO) is dispersed. At the concentration typically used in detergents, LAS is in a worm-like micellar phase exhibiting a Maxwellian behavior. The presence of HCO fibers provides elastic properties, such that the system behaves as a simple Zener body, mechanically characterized by a parallel connection of a spring and a Maxwell element. Despite this apparent independence of the contributions of the fibers and the surfactant medium to the mechanical characteristics of the system, we find that the low frequency modulus increases with increasing LAS concentration. This indicates that LAS induces attractive interactions among the HCO fibers, resulting in the formation of a stress-bearing structure that withstands shear at HCO concentrations, where the HCO fibers in the absence of attractive interactions would not sufficiently overlap to provide stress-bearing properties to the system.

Impact of shear on the structure and rheological properties of a hydrogenated castor oil colloidal gel during dynamic phase transitions

Rheological modifiers are subject to processing steps, including mixing and dilution, that can have permanent structural effects. This work investigates rheological changes of a fibrous colloid, hydrogenated castor oil (HCO), when sheared during sample preparation. HCO is a polydisperse system that undergoes phase transitions in response to osmotic pressure gradients. Two HCO materials are characterized during phase transitions, a nonsheared 4 wt. % gel and a presheared 0.125 wt. % solution. Material properties are measured using multiple particle tracking (MPT) microrheology, μ2rheology, the combination of microfluidics and MPT, and bulk rheology. MPT quantitatively determines the critical relaxation exponent, n, which is constant for a material. MPT determines n is dependent on the starting HCO material, indicating that preshear has changed the structure. μ2rheology identifies consistent equilibrium states during consecutive phase transitions. Bulk rheology determines that the nonsheared gel does not completely degrade into a sol, indicated by no G′ and G″ crossover. The presheared material has a crossover indicating a sol-gel transition. The phases of HCO are identified by comparison of rheological data to previous work by Wilkins et al. [Langmuir 25, 8951–8959 (2009)], who determined the structure of a similar colloidal fiber system using confocal microscopy. The equilibrium moduli at the completion of both experiments are similar and indicate that the scaffold is in a transitional phase. These three techniques give consistent measurements of the rheological properties, and indicate the structure of the scaffold by comparison to previous works. During degradation, nonsheared HCO gels change from entangled networks to a transitional state with fiber entanglement. During gelation, presheared HCO solutions transition from bundles in solution to an associated network of bundles with few entanglements. These measurements confirm that shear history can permanently change rheological properties, affecting the scaffolds applications.Rheological modifiers are subject to processing steps, including mixing and dilution, that can have permanent structural effects. This work investigates rheological changes of a fibrous colloid, hydrogenated castor oil (HCO), when sheared during sample preparation. HCO is a polydisperse system that undergoes phase transitions in response to osmotic pressure gradients. Two HCO materials are characterized during phase transitions, a nonsheared 4 wt. % gel and a presheared 0.125 wt. % solution. Material properties are measured using multiple particle tracking (MPT) microrheology, μ2rheology, the combination of microfluidics and MPT, and bulk rheology. MPT quantitatively determines the critical relaxation exponent, n, which is constant for a material. MPT determines n is dependent on the starting HCO material, indicating that preshear has changed the structure. μ2rheology identifies consistent equilibrium states during consecutive phase transitions. Bulk rheology determines that the nonsheared gel does not co...

The rising motion of spheres in structured fluids with yield stress

The rising of spherical bodies in structured fluids with yield stress is studied. The system is a suspension of hydrogenated castor oil colloidal fibers in a surfactant micellar solution. The fiber network confers to the fluid a viscoelastic behavior, with a well-defined yield stress, which increases with increasing fiber concentration. Various fluids with different fiber contents are prepared and rheologically characterized. A home-made time-lapse photography setup is used to monitor the time evolution position of the spherical particles, and the rising motion of both hollow spheres and air bubbles, in the diameter range 65–550 μm, is measured. The experiments last as long as several weeks, corresponding to significantly low measured velocities. Finite element simulations are performed to support the experimental data, assuming both interfacial slip and no slip conditions. The fluid dynamic phenomenon is studied and discussed in terms of dimensionless numbers, such as yield ratio, Bingham number, and Stokes drag coefficient. The results are novel for the system (suspending medium and hollow spheres) and for the covered Bingham number range, which is extended over three orders of magnitude in comparison with already available literature results. Our values provide quantitative data of the mechanical properties (i.e., yield stress value) at very low shear rates, in a prohibitive range for a traditional rheometer, and agree with the macroscopic rheological response. Moreover, the important role of the power law index n of the Herschel-Bulkley model, used to fit the data, has been highlighted. Our results, based on a Bingham-like fluid, are compared with the experimental data already available with Carbopol, treated as a Herschel Bulkley fluid with n = 0.5. The results could have important implications in the fabric and personal care detergency, a technological area where many fluids have composition and show rheological properties similar to those considered in the current work.

Surface freezing and surface coverage as key factors for spontaneous formation of colloidal fibers in vacuum drying of colloidal suspensions.

In this study, we investigated vacuum drying of droplets of colloidal suspension. Because of the loss of the latent heat of vaporization, the drying droplet was cooled and then formed ice. Colloidal fibers consisting of packed particles spontaneously formed when the droplet froze from the gas-liquid interface. Conversely, we observed formation of sponge-like porous structures of particles when the whole droplet almost simultaneously froze. However, the freezing mode was not the only factor for formation of colloidal fibers. We found that the surface coverage of particles on the gas-liquid interface was also important. Owing to drying, some particles accumulated at the interface before freezing. When the surface coverage was higher than a threshold value, formation of fibers was severely restricted even in the surface freezing mode. Our results clearly show the important roles of surface freezing and the surface coverage of particles on the gas-liquid interface in formation of colloidal fibers.

Structural Coloration of Colloidal Fiber by Photonic Band Gap and Resonant Mie Scattering.

Because structural color is fadeless and dye-free, structurally colored materials have attracted great attention in a wide variety of research fields. In this work, we report the use of a novel structural coloration strategy applied to the fabrication of colorful colloidal fibers. The nanostructured fibers with tunable structural colors were massively produced by colloidal electrospinning. Experimental results and theoretical modeling reveal that the homogeneous and noniridescent structural colors of the electrospun fibers are caused by two phenomena: reflection due to the band gap of photonic structure and Mie scattering of the colloidal spheres. Our unprecedented findings show promise in paving way for the development of revolutionary dye-free technology for the coloration of various fibers.

Fabrication of Structurally-Colored Fibers with Axial Core–Shell Structure via Electrophoretic Deposition and Their Optical Properties

Structurally colored fibers were fabricated using different-sized polystyrene (PS) nanospheres via electrophoretic deposition on conductive carbon fiber surfaces. The reflective spectra corresponding to different colors were taken by microzone and angle-resolved spectrometers from a single colloidal fiber. As confirmed by structural analysis, the outer layer of the core-shell colloidal fibers consisted of face-centered cubic (f.c.c.) domains without long-range order. It is revealed that the absence of long-range order in the colloidal assembly caused isotropic reflection in radial and longitudinal directions on the colloidal fibers. Furthermore, due to the incorporation of random defects during growth process, the experimental spectra are blue-shifted and broad compared to reflective spectra calculations based on the curved f.c.c. structure. This technique is speculated to have potential application in structural coloration and radiation-proof fabrics.

Structural Evolution of Electrospun Composite Fibers from the Blend of Polyvinyl Alcohol and Polymer Nanoparticles

Electrospinning provides a versatile method for generating fibrous materials from a large variety of substances, including polymers, composites, proteins, and nano/microcolloids. In particular, the incorporation of nano/microparticles with polymeric materials is beneficial to many of electrospun fibers with multiple functionalities. This report evaluates the spinnability of a polymer solution containing polymer nanoparticles obtained through electrospinning. Tunable structures of electrospun composite fibers were obtained from a blended solution of polyvinyl alcohol (PVA) and polystyrene nanospheres (PSNs). The in-fiber arrangements of polymer nanoparticle fibers, influenced by the PVA:PSN weight ratio, and the viscosity of the blended solution and the size of PSNs were systemically studied. Once PVA was determined to dominate the solution, the diameter of the electrospun PVA fibers was comparable to the diameters of the colloidal particles, which confined the nanospheres into string-on-bead and necklace-like structures. When PSNs occupied a large portion of the solution, PVA wrapped the PSNs, forming a blackberry-like aggregate and a uniform colloidal fiber. The results from the colloid electrospinning serve as references in the creation of novel composite fibers involving various polymer nanoparticles via electrospinning. The obtained composite fibers of the polymers and colloids are expected to have potential application in various areas.

Palm Date Fibers: Analysis and Enzymatic Hydrolysis

Waste palm dates were subjected to analysis for composition and enzymatic hydrolysis of their flesh fibers. The fruit contained 32% glucose and 30% fructose, while the water-insoluble fibers of its flesh consisted of 49.9% lignin and 20.9% polysaccharides. Water-insoluble fibers were settled to 55% of its initial volume in 12 h. The presence of skin and flesh colloidal fibers results in high viscosity and clogging problems during industrial processes. The settling velocity of the fibers was improved by enzymatic hydrolysis. Hydrolysis resulted in 84.3% conversion of the cellulosic part of the fibers as well as reducing the settling time to 10 minutes and the final settled volume to 4% of the initial volume. It implies easier separation of the fibers and facilitates fermentation processes in the corresponding industries. Two kinds of high- and low-lignin fibers were identified from the water-insoluble fibers. The high-lignin fibers (75% lignin) settled easily, while the low-lignin fibers (41.4% lignin) formed a slurry suspension which settled very slowly. The hydrophilicity of these low-lignin fibers is the major challenge of the industrial processes.

Colloidal Crystal Wires

Colloidal crystals have been extensively applied in many areas of science and technology. They can be used as amodel of crystal order and phase transition processes of atoms and molecules. As the size of colloidal particles, of customary use, are in the micrometer and sub-micrometer regimes, they produce strong diffraction effects in the optical region. This effect has been, and is still being, extensively applied to several fields of research such as photonic crystals and sensors. Diffraction effects are dependent on the type of crystal order, that is, on the point group symmetry by which colloids are ordered. Hard-sphere colloidal particles order in closedpacked assemblies with preference for the face-centered cubic (fcc) symmetry. However, the crystallization process of colloidal suspensions in confined geometries is very different from that in bulk systems. So far, most of the work in this area has focused on colloidal crystal thin films, which corresponds to one-dimensional confinement, where different types of close-packed and non-closed-packed facets appear. In the case of two-dimensional confinement, colloidal crystal wires (CCW) are obtained. The important parameter to be considered here is the ratio between the confinement size and particle diameter, which we call the confinement ratio D. There are two limiting cases depending on the value. When D! 1, particles arrange themselves in a wide range of close-packed structures depending of the geometric shape of the template. For example, squarelike colloidal fibers were obtained with lithographically prepared open channels templates, as well as with square-shaped optical fibers. Also, a colloidal crystal capillary column has recently been reported. New colloidal crystal arrangements appear when the patterned substrates have a lateral dimension similar to the particle size, that is, when D 1. Then, non-close-packed structures are favored and, in some cases, helical ordering is induced. But, most of all above cases do not show a pure 2D confinement, because they concern particle ordering into open patterned templates. Spheres distribute themselves in wirelike manner as has been modelled by Ericksson and Picket et al., through a hard-sphere packingmodel, and then shown for samples with beads in the millimeter range. These authors have demonstrated that, depending on the factor, particles pack themselves in a manifold variety of pattern configurations. Owing to their potential applications, colloidal crystals fibres have raised great interest. Also, they can be used as a model for the formation of chiral molecules as liquid crystals or DNA. Following these seminal works, some groups have reported experimental results on the arrangement of spherical particles into cylindrical pores in a broad length scale ranging from 100 micrometers up to the nanometer range. Recently, another approach that concerns the infiltration of particles into porous membranes made of alumina or silicon has been reported. Free-standing CCW were obtained. Although in most cases random packing geometries were observed, some fibers show helical twist, a fingerprint of chirality. However, to the best of our knowledge, no systematic experimental study of the influence of the parameter on the particle order has been published. Herein, we report on the infiltration of polystyrene (PS) spheres inside the pores of a siliconmembrane with a similar procedure to that employed by Wiley et al. We have performed a careful study of the particle arrangement for values between 1 and 3. As we have employed chargestabilized colloidal particles, the hard sphere model can not account for the experimental results. However, it will be used as a guide to understand particle arrangements. Figure 1 shows a scheme of the method to produce CCWs (see Experimental for more details). Sulphate-stabilized PS spheres were infiltrated into the silicon membrane. To cover the parameter values described above, a combination of PS spheres with different diameters (1, 1.2, and 1.5mm) and high-quality porous silicon membranes with a pore diameter between 2 and 4mm were used. The silicon membrane was manufactured by means of an electrochemical etching procedure. Such a C O M M U N IC A IO N

Character and stability of colloidal substances in a mechanical pulp suspension

Dispersed colloidal substances present in aqueous suspensions of unbleached thermomechanical pulp were studied by transmission electron microscopy and by flocculation experiments. The colloidal substances were primarily lipophilic extractive droplets and colloidal fiber fragments. When larger colloidal fiber fragments were removed by ultracentrifugation the stability of the lipophilic droplets against flocculation and sedimentation with cationic polyelectrolytes was enhanced.

Electron microscopic study on the laryngeal polyp (author's transl)

Various reports have been published on the causative factors of polyp of the vocal cords. In the present study, laryngeal polyps were examined by optical and electron microscopy, with special respect on the allergic reactions which are regarded a one of its possible causative factors.For electron microscopic examination, materials were stained with PAM.or Ruthenium Red, which are usually employed to demonstrate mucopolysaccharides.This study was conducted on the 124 patients with laryngeeal polyp who visited our clinic during the five year period from April, 1970 to March, 1975.All of their polyps were removed by laryngo-micro surgeny NLA.The results were as follows.1) Clinical ExaminationThe polyps were most frequently found in the anterior and middle one-third of the vocal cords (about 50 %).It can be said that this is due to the distribution of blood vessels, specifi- city of vascular structure, and the torsional movement of the vocal cords muscules.2) Electron Microscopic Observations Electron microscopic examination revealed the degeneration and dilatation of intercellular space of mucosal epithelium and intracellular edema.In the mucosal matrix, dilatation of micro- vasculature, hemangioma-like degeneration, and perivascular infiltrations of histiocytes or other mononuclear cells were noted.Moreover, marked microfiber and fibrostic substances were observed.In many cases, an increase in the acidic mucopolysaccharides and PAM-stain positive colloidal fiber in the matrix were noted, as well as an increase of the capillary permeability. Although various reports have been published, on the causative factors of the polyp of the vocal cords, it can be said that the disease may be caused by various factors rather than by a single factor.In this study, detailed electron microscopic observation was made on the shaft like structure which is specific for the peripheral blood vessels in the vocal cords and found that immunolo- gical factors are important in the pathogenesis of this disease.The local abnormalities and the specificity of blood vessels of the vocal cords are also important factors.