Polymer Microfibers Research Articles

Fusion of polymer-coated liposomes and centrifugally spun microfibers as hybrid materials to enhance sustained release.

Liposomes are employed for the delivery of molecular cargo in several classes of systems. For instance, the embedding of loaded liposomes in polymeric fibrous scaffolds has enabled the creation of hybrid materials that mimic biological membranes. Liposomes with unmodified surfaces have been predominantly integrated into fibers, which leads to instabilities due to interfacial incompatibility. In addition, electrospinning has been almost exclusively employed for fiber fabrication, which limits the potential for scale-up production. Here, we present the fabrication of hybrid biomimetic materials by fusing polymer-coated liposomes to force-spun microfibers to increase the stability of the hybrid materials and enhance the sustained release of the cargo. l-α-Phosphatidylcholine liposomes were coated with chitosan or polyethylene glycol (PEG). The nano-differential scanning calorimetry results confirm that polymer coating does not affect the phase transition temperature (T m) of the liposomes, where only the model drug, quercetin, reduced T m. Centrifugal spinning was employed to fabricate hydrophobic polycaprolactone (PCL) microfibers at various polymer concentrations and using various solvents and spinning parameters to increase the yield at the lowest fiber diameter. The highest microfiber production rate obtained occurred at a 20% (w/v) PCL concentration in 50 : 50 (v/v) chloroform and methanol solution with an average fiber diameter of 584.85 ± 26.30 nm. The non-chemical fusion of the polymer-coated liposomes and the fibrous scaffolds was promoted by immersion at T > T m, under ultrasonication. We hypothesize that the fusion is driven by hydrophobic interactions between the liposomes and the fibers, which merge the materials through the lipid bilayer. The fused hybrid material solved the burst release problem observed when adhering plain liposomes to nanofibers. Both PEG and chitosan yielded a sustained release, where the release rate with the former was faster. These results demonstrate that the fusion of polymer-coated liposomes and microfibers enables more effective blending of the loaded carriers into the polymer microfibers. Ultimately, the fused liposome/microfiber hybrids are stable matrices and enhance the sustained release of molecular cargo.

Conductive Microfibers Improve Stem Cell‐Derived Cardiac Spheroid Maturation

ABSTRACTConventional two‐dimensional (2D) cardiomyocyte differentiation protocols create cells with limited maturity, which impairs their predictive capacity and has driven interest in three‐dimensional (3D) engineered cardiac tissue models of varying maturity and scalability. Cardiac spheroids are attractive high‐throughput models that have demonstrated improved functional and transcriptional maturity over conventional 2D differentiations. However, these 3D models still tend to have limited contractile and electrical maturity compared to highly engineered cardiac tissues; hence, we incorporated a library of conductive polymer microfibers in cardiac spheroids to determine if fiber properties could accelerate maturation. Conductive microfibers improved contractility parameters of cardiac spheroids over time versus nonconductive fibers, specifically, when they were short, for example, 5 μm, and when there was moderate fiber mass per spheroid, for example, 20 μg. Spheroids with optimal conductive microfiber length and concentration developed a thicker ring‐like perimeter and a less compacted cavity, improving their contractile work compared to control cardiac spheroids. Functional improvements correlated with increased expression of contractility and calcium handling‐related cardiac proteins, as well as improved calcium handling abilities and drug response. Taken together, these data suggest that conductive microfibers can improve cardiac spheroid performance to improve cardiac disease modeling.

Polymeric Nanofibers and Microfibers: New Formats of Materials Used in Chromatography for Sample Preparation Using Solid Phase Extraction

For traditional sample preparation by solid phase extraction prior to HPLC separation, plastic or metal pre-columns filled with sorbent particles or, more recently, monolithic columns are commonly used. To a much lesser extent, fibrous sorbents are used for this purpose. This article aims at introducing the reader to the possibilities offered by fibrous sorbents in the field of analytical chemistry. Methods for the production of nanofibers and microfibers using electrospinning, meltblown, and their combination are described. These are also presented with a brief look at the history of their development. Examples of the polymers which the fibers are prepared from and their characteristics, which must be considered when selecting the polymer for extraction of the desired analytes, are also listed. Finally, some examples of extraction of substances presented in our publications are described, with a particular focus on samples that are complex in nature, such as the environmental and biological samples.

Thermal diffusivity measurement of polymer microfibers while eliminating the effect of heat radiation

The thermal transport properties of polymer fibers are important for heat dissipation in apparel, matrix of wearable devices, and so on. However, it is difficult to precisely determine the thermal properties of a single polymer fiber because of non-negligible thermal radiation due to its relatively low thermal conductivity and high surface-area-to-volume ratio. Here, we developed a system in which the apparent thermal diffusivity and size of microfibers can be measured to estimate their intrinsic thermal diffusivity. We determined the thermal diffusivities of three fibrous materials: silk, spider silk, and cellulose microfibers to be 4.2 (±0.8)×10−7, 1.8 (±0.7)×10−7, and 4.7 (±0.5)×10−7, respectively. For all fibers, the apparent thermal diffusivity strongly depended on the fiber size, indicating that eliminating the radiation effect is indispensable for determining the thermal transport properties of polymer microfibers.

3D Micropatterning With Thermochromic Polymer Microfiber

AbstractAlthough 3D micropattern has received considerable attention due to their remarkable usability, the introduction of specific functions, such as “chromism”, is still a challenge mainly due to the lack of adequate functional materials that can be introduced into 3D printing system. In this study, 3D micropatterns with temperature‐responsive properties are created by elaborately aligned thermochromic polymer microfibers using charge reversal electro‐jet writing (CREW) method with a 3D printer. A reversible color change in response to the temperature change is exhibited in the micropattern, displaying various chromic colors, such as red, blue, and black, at their own thermochromic temperatures. Multiple‐color phases can be sequentially expressed in a single structure by incorporating pigments of different colors with distinguishable color shift ranges. Various patterning methods are proposed for manufacturing diverse patterns and demonstrating applications using combinations of color. In addition to directly increasing temperature, the thermochromic process of micropatterns can be induced by heat generated from external factors using electrical energy. These 3D thermochromic micropatterns using the CREW method can be extended to various fields, including sensors, clothing, and anti‐counterfeiting.

Evaluation of Mortars Performance with Electrospun Polymeric Microfibers Addition from PET and PVB Waste

Evaluation of Mortars Performance with Electrospun Polymeric Microfibers Addition from PET and PVB Waste

Antibacterial and antiviral PA6-AgNPs microfibers for application as a filter element in facial respirators

Polymeric microfibers are very interesting materials that can be associated with other nanomaterials aiming to obtain specific properties and be used in a wide range of applications. In this study, we prepared different formulations of polyamide 6 (PA6) containing silver nanoparticles (AgNPs) and produced microfibers by solution blow spinning technique for its use as a filter element in a face respirator. The obtained samples were then characterized by field emission gun-scanning electron microscopy (FEG-SEM), energy dispersion spectroscopy (EDS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), water contact angle (WCA), thermogravimetric analysis (TGA), and respirability and antibacterial, antiviral and cytotoxicity assays. In general, the microfibers were well dispersed and the AgNPs were evenly distributed throughout the samples, reflecting a hydrophilic character and good thermal stability, with a maximum weight loss of 2.9 % attributed to the evaporation of water molecules. The sample produced with a concentration of 10 mmol/L of silver nitrate presented acceptable levels of resistance to respiration. Concerning the microbiological analyses, the results showed that samples evidenced antibacterial effect against Escherichia coli and Staphylococcus aureus, forming inhibition halos of up to 4 mm in disk diffusion assays and inhibiting bacterial growth in liquid medium assays, as well as antiviral effect against betacoronavirus MHV-3, promoting a reduction of up to 99.9 % of viral particles. Moreover, the samples presented cytotoxicity on the first and second days, whereas on the seventh day some of the extracts did not show cytotoxic activity, indicating that the cells adapted to the culture medium. Considering the data set and the simple process of obtaining the microfibers, it was possible to conclude that this material can be applied as a filter element in a face respirator as well as in a variety of products with antibacterial and antiviral purposes.

Artificial Muscles Based on Coiled Conductive Polymer Yarns

AbstractLightweight artificial muscles with large strain and large stress output have great application prospects in robotics, rehabilitation, prosthetic, and exoskeletons. Despite the excellent performance of carbon nanotube‐based artificial muscles in recent years, their widespread use is hindered by the high manufacturing costs associated with carbon nanotubes. In this paper, the study introduces a novel approach by developing artificial muscles based on pure conductive polymer coiled yarns. This achievement is facilitated by the successful fabrication of high‐strength conductive polymer microfibers. Furthermore, the study elucidates the molecular structural changes occurring during electrochemical processes that induce a substantial radial volume expansion in the microfibers. The resultant anisotropic volume change is magnified by the coiled yarn, yielding a remarkable contractile strain exceeding 11% at a high stress of 5 MPa, equivalent to lifting loads more than 4000 times their own masses, all achieved with a low input voltage of 1 V. Additionally, these conductive polymer‐based artificial muscles exhibit hydration‐induced contraction up to 33%, with swift recovery through electrical heating, leveraging their intrinsic high conductivity. This breakthrough positions high‐performance conductive polymer microfibers as a promising cost‐effective alternative to carbon nanotubes, establishing them at the forefront of lightweight artificial muscles.

Materials and Strategies to Enhance Melt Electrowriting Potential.

Melt electrowriting (MEW) is an emerging additive manufacturing (AM) technology that enables the precise deposition of continuous polymeric microfibers, allowing for the creation of high-resolution constructs. In recent years, MEW has undergone a revolution, with the introduction of active properties or additional functionalities through novel polymer processing strategies, the incorporation of functional fillers, postprocessing, or the combination with other techniques. While extensively explored in biomedical applications, MEW's potential in other fields remains untapped. Thus, this review explores MEW's characteristics from a materials science perspective, emphasizing the diverse range of materials and composites processed by this technique and their current and potential applications. Additionally, the prospects offered by postprinting processing techniques are explored, together with the synergy achieved by combining melt electrowriting with other manufacturing methods. By highlighting the untapped potentials of MEW, this review aims to inspire research groups across various fields to leverage this technology for innovative endeavors.

Facilely Fabricated Porous Polymer Microfiber Tube Toward Continuous Oil-Water Separating

Serious ocean oil spills have led to shocking ecological disasters and environmental crises over the past few decades. However, owing to their intermittent mode, the present oil/water separation and collection processes generally suffer from time-consuming, complicated and expensive steps. Therefore, it is urgent to propose a facile way to consecutively separate and collect oil from oil-water mix in a one-step way. Herein, via coextrusion molding, the porous polymer (high desity polyethylene (HDPE)) microfiber tube (PPMT) was facilely fabricated. It shows high porosity (76.2±4.1%), excellent oleophilicity (OCA of 0ž) and good hydrophobicity (WCA of 135ž), resulting in decent absorption capacity of various organic pollutants (in the range of 170–350 wt.%). More interestingly, it is able to consecutively separate and collect oil from following oil-water mix and avoids secondary operation (such as extra desorption), successfully achieving efficient one-step method for oil-water separating & collecting (with a separation efficiency of 97.4%±4.7% at the average flux of 0.28 ml/s). This work proposes a novel concept for preparing porous polymer tube composed of microfibrils via a low-cost, facile and effcient method, offering an innovative way to construct the functional structure following the idea of polymer “structuring” processing.

A Review on the Electrospinning of Polymer Nanofibers and Its Biomedical Applications

Polymeric nanofibers have emerged as a captivating medium for crafting structures with biomedical applications. Spinning methods have garnered substantial attention in the context of medical applications and neural tissue engineering, ultimately leading to the production of polymer fibers. In comparison with polymer microfibers, polymer nanofibers boasting nanometer-scale diameters offer significantly larger surface areas, facilitating enhanced surface functionalization. Consequently, polymer nanofiber mats are presently undergoing rigorous evaluation for a myriad of applications, including filters, scaffolds for tissue engineering, protective equipment, reinforcement in composite materials, and sensors. This review offers an exhaustive overview of the latest advancements in polymer nanofiber processing and characterization. Additionally, it engages in a discourse regarding research challenges, forthcoming developments in polymer nanofiber production, and diverse polymer types and its applications. Electrospinning has been used to convert a broad range of polymers into nanoparticle nanofibers, and it may be the only approach with significant potential for industrial manufacturing. The basics of these spinning techniques, highlighting the biomedical uses as well as nanostructured fibers for drug delivery, disease modeling, regenerative medicine, tissue engineering, and bio-sensing have been explored.

Simultaneous photo-induced polymerization and surface modification by microfluidic spinning to produce functionalized polymer microfibers: the effect of their surface modification on cell adhesion

A capillary-based microfluidic device is used to prepare functionalized polymer microfibers in one-step involving monomer photopolymerization in the core phase and surface modification of the fibers by thiol-acrylate reactions at the interface.

Directional actuation and phase transition-like behavior in anisotropic networks of responsive microfibers.

Two-dimensional shape-morphing networks are common in biological systems and have garnered attention due to their nontrivial physical properties that emanate from their cellular nature. Here, we present the fabrication and characterization of anisotropic shape-morphing networks composed of thermoresponsive polymeric microfibers. By strategically positioning fibers with varying responses, we construct networks that exhibit directional actuation. The individual segments within the network display either a linear extension or buckling upon swelling, depending on their radius and length, and the transition between these morphing behaviors resembles Landau's second-order phase transition. The microscale variations in morphing behaviors are translated into observable macroscopic effects, wherein regions undergoing linear expansion retain their shape upon swelling, whereas buckled regions demonstrate negative compressibility and shrink. Manipulating the macroscale morphing by adjusting the properties of the fibrous microsegments offers a means to modulate and program morphing with mesoscale precision and unlocks novel opportunities for developing programmable microscale soft robotics and actuators.

Colloidal Nanoplatelets‐Based Soft Matter Technology for Photonic Interconnected Networks: Low‐Threshold Lasing and Polygonal Self‐Coupling Microlasers

AbstractSoft matter‐based microlasers are widely regarded as excellent building blocks for realizing photonic interconnected networks in optoelectronic chips, owing to their flexibility and functional network topology. However, the potential of these devices is hindered by challenges such as poor lasing stability, high lasing threshold, and gaps in knowledge regarding cavity interconnection characteristics. In this study, the first demonstration of a high‐quality, low‐threshold nanoplatelets (NPLs)‐based polymer microfiber laser fabricated using capillary immersion techniques and its photonic interconnected networks are presented. CdSe/CdS@Cd1‐xZnxS core/buffer shell@graded‐shell NPLs with high optical gain characteristics are adopted as the gain medium. The study achieves a lasing threshold below 14.8 µJ cm−2, a single‐mode quality (Q)‐factor of ≈5500, and robust lasing stability in the fabricated NPLs‐based microfibers. Furthermore, the study pioneers the exploration of polygonal self‐coupling microlasers and the optical characteristics of their interconnected fiber network. Based on the signal generation mechanism observed in the photonic networks, an interconnected NPLs‐based fiber network structure achieving single‐mode lasing emission and laser mode modulation is successfully designed. The work contributes a novel method for realizing microlasers fabricated via soft‐matter technologies and provides a key foundation and new insights for unit design and programming for future photonic network systems.

Two wavelength band emission WGM lasers via photo-isomerization.

Wavelength switchable microcavity is indispensable component for various integrated photonic devices. However, achieving two wavelength band emission of the whispering gallery mode (WGM) laser is challenging. Here, we propose a strategy to realize two wavelength band emission WGM lasers activated by photo-isomerization based on excited-state intramolecular proton transfer (ESIPT) process in isolated/coupled polymer microfiber cavities. The WGM microcavity is built by highly polarized organic intramolecular charge-transfer (ICT) dye molecules. The two cooperative gain states of ICT dye molecules can be controlled by optimizing energy levels. Thereby, the lasing wavelength can be reversibly switched under photo-isomerization activated in the ESIPT energy-level progress. The photonic bar code can be generated by following the strategy of proposed design. This work provides a promising route to achieve switchable WGM laser in on-chip photonic integration.

Gentamicin Release Study in Uniaxial and Coaxial Polyhydroxybutyrate-Polyethylene Glycol-Gentamicin Microfibers Treated with Atmospheric Plasma.

The skin is the largest organ and one of the most important in the human body, and is constantly exposed to pathogenic microorganisms that cause infections; then, pharmacological administration is required. One of the basic medical methods for treating chronic wounds is to use topical dressings with characteristics that promote wound healing. Fiber-based dressings mimic the local dermal extracellular matrix (ECM), maintaining an ideal wound-healing climate. This work proposes electrospun PHB/PEG polymeric microfibers as dressings for administering the antibiotic gentamicin directed at skin infections. PHB-PEG/gentamicin fibers were characterized before and after plasma treatment by Raman spectroscopy, FTIR, and XRD. SEM was used to evaluate fiber morphology and yarn size. The plasma treatment improved the hydrophilicity of the PHB/PEG/gentamicin fibers. The release of gentamicin in the plasma-treated fibers was more sustained over time than in the untreated ones.

Flexible Wet-Spun PEDOT:PSS Microfibers Integrating Thermal-Sensing and Joule Heating Functions for Smart Textiles.

Multifunctional fiber materials play a key role in the field of smart textiles. Temperature sensing and active thermal management are two important functions of smart fabrics, but few studies have combined both functions in a single fiber material. In this work, we demonstrate a temperature-sensing and in situ heating functionalized conductive polymer microfiber by exploiting its high electrical conductivity and thermoelectric properties. The conductive polymer microfibers were prepared by wet-spinning the PEDOT:PSS aqueous dispersion with ionic liquid additives, which was used to enhance the electrical and mechanical properties of the final microfibers. The thermoelectric properties of these microfibers were further studied. Due to their excellent flexibility and mechanical properties, these fibers can be easily integrated into commercial fabrics for the manufacture of smart textiles through knitting. We further demonstrated a smart glove with integrated temperature-sensing and in situ heating functions, and further explored thermoelectric fiber-based temperature-sensing array fabric. These works combine the thermoelectric properties and heating function of conductive polymer fibers, providing new insights that enable further development of high-performance, multifunctional wearable smart textiles.

The high-throughput atomization of polymer solutions for fiber synthesis in a single step aided with corona ionizers

Polymer microfibers are ubiquitous structures across virtually all technological fields. Their applications include, for instance, filter media, tissue regeneration, wound healing and dressing, and reinforcement materials. The most effective methods for fabrication of fibrous micro and nanomaterials rely on electric fields to spin a liquid jet into an ultrafine thread that rapidly dries up forming a fiber. Continuous spinning and collection leads to formation of fiber mats. Here we report a robust yet simple approach for the massive production of liquid threads, which upon acquiring electrical charges in-flight are collected downstream in the form of fibers. The entire process takes place on-line in a single step. The liquid threads are produced through the fragmentation of a polymer solution bulk due to a turbulent interaction of a gas–liquid interface in the interior of an engineered device, a so-called Flow Blurring atomizer. The particularity of this approach consists precisely in such vigorous interaction, at the micrometer scale, which triggers a bubbly motion in the interior of the device, that is a “micro-mixing”. Subsequently, the threads are passed through ionized air currents, at ambient conditions, and then stretched to sub-micrometer dimensions by electric fields. Polyvinylpyrrolidone (PVP) as well as carbon nanotubes (CNTs) or graphene oxide sheets (GOSs)-containing PVP fibers, with diameters in the range 100–900 nm, were synthesized via this approach. In the cases studied herein the method was operated at liquid flow rates (i.e. production rates) of 0.2 mL/min but it could be readily increased up to a few tens of mL/min. The method requires further improvement and optimization, nevertheless it is a promising alternative for mass production of polymer fibers.

Tuning the electrochemical response of PCL-PEDOT:PSS fibers-based sensors by gas dissolution foaming

A new procedure to enhance the performance of polymer-based electrochemical sensors is proposed in this work. Polycaprolactone (PCL) electrospun fiber mats with tunable fiber morphology are functionalized with a conductive polymer (PEDOT:PSS) by a facile dip-coting process, providing them the necessary electrical conductivity to work as sensors. The modification of the fiber morphology is achieved by an enhanced gas dissolution foaming procedure, an environmentally friendly procedure that employs CO2 as blowing agent and takes advantage of recent advances that allowed extending such procedure to polymeric microfibers. Thus, the enhanced gas dissolution foaming approach was employed both before and after the coating of the fiber mats with PEDOT:PSS, producing in both cases hollow fibers with enhanced surface porosity and area, as well as increased diameter regarding the initial solid PCL fibers. The addition of PEDOT:PSS, both in solid and foamed PCL fibers, allows their use as sensors, as proved by cyclic voltammetry in a KCl solution, as well as calibrated with catechol solutions. Remarkable influence of the foaming procedure on the performance of the sensors have been found, proving by a detailed characterization that the foaming procedure applied after the PEDOT:PSS coating provides an enhanced sensoring response (i.e., increased signal, optimal linearity, decreased LOD) due to their superior surface area and optimal PEDOT:PSS distribution along the fiber mats, not only covering the external surface of the fibers but infusing into the inner regions.

Preparation of high positioning accuracy lattice patterns with polymeric microfibers derived from near‐field electrospinning

AbstractElectrospinning is a straightforward and versatile technology that has been broadly applied to the preparation of microfibers. However, the fabrication of complicated patterns with high positioning accuracy is still a challenge. The enhancement of the positioning accuracy is restricted by the bending instability of the jet and the motion stage. Here, an effective method to improve the positioning accuracy of ordered fibers by optimizing printing parameter and printing order is proposed. Highly oriented and uniformly aligned microfiber arrays composed of polyethylene oxide (PEO) fibers with a diameter of 2.8 ± 0.13 μm are deposited by adjusting the process parameters. Moreover, the accumulative return error of the printed pattern was reduced by 30.54 μm in X‐axis and 55.59 μm in Y‐axis using an optimized printing order. The lattice patterns with a high positioning accuracy of 0.98 ± 0.06 μm were obtained, which is nearly two orders of magnitude higher than that of the structure with unoptimized printing order. Results indicate that the method can significantly improve the positioning accuracy of the lattice patterns of polymeric microfibers, which has a promising prospect in the field of high‐precision micro manufacturing.