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Abstract Electrospinning is a versatile technique to fabricate non-woven fiber mats with an average fiber diameter ranging from nanometers to micrometers. Fibers produced by electrospinning have potential application in numerous fields owing to their light weight, high surface area, and high porosity. In certain applications, anisotropic properties are desired, which may also improve mechanical strength. This study comprehensively documented the feasibility of directed fiber deposition in wet-electrospinning and offers an inexpensive setup for laboratory investigation. Aligned starch fiber mats were produced and the effects of three operational parameters, i.e., rotational speed, drum location, and coagulation bath composition, were evaluated. The alignment of starch fibers was affected by the ethanol concentration in the coagulation bath and drum rotational speed. Coherent fibers could be obtained in all trials except for the one at the lowest ethanol concentration (60% v/v) and highest rotational speed (500 rpm) when the drum was below the liquid. The tensile strength was influenced by the interaction of location and ethanol concentration, and that of rotational speed and ethanol concentration. This study set a promising example of making aligned biopolymer fiber mats and investigating fiber deposition in wet-electrospinning. Aligned starch fiber mats have potential applications in areas such as tissue engineering and as wound dressings. Graphical abstract Image 104 Highlights • A benchtop setup for making aligned wet-electrospun fiber mats was developed. • Effects of operational parameters in wet-electrospinning were evaluated. • The tensile strength of fiber mat increased with fiber alignment. [ABSTRACT FROM AUTHOR]

Abstract Electrospinning has become an increasingly attractive technique to produce micro-to nano-scale fibers from bio-based polymers, including starch. Compared to their synthetic counterparts, fibers electrospun from bio-based polymers generally have inferior mechanical strength. In the present study, we aim to enhance the mechanical strength of electrospun starch-based fibers by using nanocellulose as a reinforcing filler and cationic starch as a binding agent. The potential ionic bonding between cationic starch and anionic nanocellulose, and the hydrogen bonding as well as macromolecular entanglement between the three components, are expected to improve the compatibility of polymers and the mechanical strength of their composite fibers. Rheological properties of nanocellulose, cationic starch, and their mixtures were studied to understand their conformation and interaction in DMSO dispersions. The rheological properties of the ternary systems were studied and correlated with their electrospinnability and the tensile strength of the composite fiber mats. Our results suggested that nanocellulose-cationic starch at its percolation concentration (≈2%, w/w, of starch) has the most profound influence on fiber strength, and CS:NC ratios of 1:2 and 1:1 created improved intermolecular ionic bonding for reinforcing the fiber structure. Graphical abstract Image 1 Highlights • Tensile strength of electrospun starch fiber mats increased using nanocellulose filler and cationic starch as a binding agent. • Rheological behavior of individual, binary, and ternary biopolymer blends was evaluated to guide electrospinning process. • NC CS at its percolation concentration (≈2%, w/w, of starch) had the most influence on electrospun fiber strength. [ABSTRACT FROM AUTHOR]

Electrospun starch fiber mats have many potential applications, but an improvement in their mechanical properties is required to realize them. In the present study, wet-electrospun starch fiber mats were subjected to post-drying conditioning at controlled equilibrium relative humidity and equilibration time. The weight-normalized ultimate tensile strength of starch fiber mats increased significantly with equilibration at relative humidity >0.75 after 28 days. Morphological observation and X-ray diffraction analysis excluded significant changes in fiber size or crystallinity, and thus we concluded that conglutination brought about by the plasticizing effect of water and observed microscopically was primarily responsible for this mechanical improvement. [ABSTRACT FROM AUTHOR]

Abstract: Electro-wet-spinning was used to fabricate continuous nonwoven microscale and nanoscale fibers from pullulan. We investigated the rheological properties of pullulan dispersions using DMSO:water mixtures as solvents with varying compositions. The relationship between electrospinnability and rheological properties were studied. In order to obtain well-formed pullulan fibers, the concentration of pullulan dispersion had to be 1.88–2.25 times the entanglement concentration, depending on DMSO:water ratio in the solvent. Shear viscosity was another important factor. The shear viscosities at 100 s−1 of electrospinnable pullulan dispersions fell into a range between 0.06 and 2.2 Pa s, regardless of solvent composition. Yet, there may still be other factors governing the fiber size as DMSO concentration changed. Pullulan fibers in the order of hundreds of nanometers to tens of microns were obtained. Increase in DMSO concentration in the solvent generally increased the fiber size and pore size in the electrospun pullulan fiber mat. [Copyright &y& Elsevier]

Abstract: We have demonstrated a method of fabricating starch fibers with an average diameter in the order of micrometers. In the present study, the formation of starch-guest inclusion complexes in the electrospun starch fibers was evaluated. Two methods were used to electrospin starch fibers with starch-guest inclusion complexes: a dope mixing method, where guest material was mixed into the starch dispersion prior to electrospinning, and a bath mixing method, where guest material was mixed into the coagulation bath into which starch dispersions were electrospun. Three selected guest compounds, palmitic acid, ascorbyl palmitate, and cetyl-trimethylammonium bromide, formed inclusion complexes with starch in the electrospun starch fibers. The presence of native lipids was not necessary to induce the inclusion complex formation. Encapsulation of these molecules in electrospun starch fibers may increase their stability during processing and storage, while providing controlled release properties. [Copyright &y& Elsevier]

Abstract: Many efforts to spin starch fibers are reported in the patent and research literature. All reported spinning methods are dependent upon addition of non-starch components, e.g. other polymers, plasticizers or cross-linkers. In the present study, we demonstrate a method of producing pure starch fibers by an electrospinning technique. This method involves choosing an appropriate solvent for native high amylose starch and spinning on a modified electrospinning setup. Resulting starch fibers have diameters in the order of microns. Coagulation solvent composition can affect the crystallinity of the starch fibers. Post-spinning treatments were employed to increase the crystallinity and cross-link the starch fibers. The novel starch fibers have potential in various applications, e.g. in the food, textile, and biomedical industries. [Copyright &y& Elsevier]

Abstract: The diameter of the starch fibers produced by electrospinning is a key parameter for most potential applications. In this study, a quantitative relationship between fiber diameter and certain electrospinning parameters, i.e. starch concentration, applied voltage, spinning distance and feed rate, was established by empirical modeling using a fractional factorial experimental design in a constrained region. Response surface methodology was employed to analyze the interactions of the electrospinning parameters and predict the direction to minimize and maximize the fiber diameters. [Copyright &y& Elsevier]

We have demonstrated a method of fabricating pure starchfiberswith an average diameter in the order of micrometers. In the presentstudy, correlation between the rheological properties of starch dispersionsand the electrospinnability was attempted via the extrapolation ofthe critical entanglement concentration, which is the boundary betweenthe semidilute unentangled regime and the semidilute entangled regime.Dispersions of high amylose starch containing nominally 80% amylose(Gelose 80) required 1.2–2.7 times the entanglement concentrationfor effective electrospinning. Besides starch concentration, molecularconformation, and shear viscosity were also of importance in determiningthe electrospinnability. The rheological properties and electrospinnabilityof different starches were studied. Hylon VII and Hylon V starches,containing nominally 70 and 50% amylose, respectively, required concentrationsof 1.9 and 3.7 times their entanglement concentrations for electrospinning.Only poor fibers were obtained from mung bean starch, which containsabout 35% amylose, while starches with even lower amylose contentscould not be electrospun. [ABSTRACT FROM AUTHOR]

• Starch-based nanofibers successfully electrospun from aqueous dispersions • Addition of pullulan aided in electrospinning of octenylsuccinylated (OS) starch • Electrospinnability of OS starches dictated mainly by rheological properties • Spinnability map of OS starch and pullulan established We aimed to develop a greener process for dry-electrospinning food-grade modified starch through the elimination of organic solvents. The rheological properties and electrospinnability of aqueous dispersions of commercial octenylsuccinylated (OS) starches with various molecular weight (Mw) were investigated, yet only nanofibers with beads or defects could be obtained from OS starch with the highest Mw, i.e., Purity Gum@ Ultra (PGU). Further improvement in the fiber morphology was achieved by adding pullulan (PUL) as a minor component in the spinning dope. Smooth, continuous, and bead-free nanofibers (147-250 nm) were obtained from the PGU-PUL dispersions. Shown on an electrospinnability map, the successful electrospinning of 12%, 15%, and 20% (w/v) aqueous PGU dispersions required a minimum addition of 6%, 5%, and 3% (w/v) of PUL, respectively. The addition of PUL contributed to establishing sufficient molecular entanglement for electrospinning. This study provides a promising green process to produce starch-based nanofibers for use in various applications, e.g., drug delivery, wound dressing, and tissue engineering. [ABSTRACT FROM AUTHOR]

Electrospinning is a simple, versatile method that employs an electrostatic force to produce fibers in the micro-to nanometer range using a wide variety of materials ranging from natural biopolymers to synthetics. Variations on the basic electrospinning set-up can be used to produce fibers demonstrating various morphological and functional properties advantageous for specific applications. Moreover, electrospun fibers created using naturally occurring polysaccharides have attracted much attention due to, but not limited to, their biological properties and sustainable sourcing. In this review, common variations on the basic electrospinning set-up are briefly discussed for their benefits in fiber morphology and upscaling capabilities. In depth, electrospun fibers made from polysaccharides; specifically alginate, cellulose, chitin and chitosan, starch, pullulan, hyaluronic acid, dextran, and levan; are discussed with an emphasis on the current research direction being taken for each of these materials. Moreover, current methods to increase electrospinnability for these polysaccharides are presented as well. Electrospun fibers can be specifically tailored for their function by the optimization of the electrospinning process and spinning dope. However, before the electrospinning process can be successfully upscaled on an industrial or commercial level, it is important to determine an effective method for increasing the rate of fiber production and, generally in the case of polysaccharides, increasing electrospinnability. Biopolymer fibers, specifically, demonstrate high potential in the biomedical field due to their biodegradability and compatibility properties. • Electrospinning technique is simple, versatile, and scalable. • Nanofibers successfully electrospun from various bio-based carbohydrate polymers. • Biopolymer nanofibers show many advantages for food and related applications. [ABSTRACT FROM AUTHOR]