Polymer Jet Research Articles

Numerical Analysis of the Airflow Field and Experiments of Fiber Motion for Solution Blowing.

Solution blowing is a rapidly developing technology for the rapid and large-scale preparation of nanofibers, driven by its advantages, such as wide adaptability to raw materials, simple and safe operation, and ease of scalable production. Most of the research related to solution blowing mainly focuses on the fiber spinning and forming principle, fiber structure and properties, and the development of new materials. Limited studies have focused on the airflow field and fiber motion in solution blowing. In this paper, nine nozzles for solution blowing with varying geometrical parameters were designed by adjusting the outer nozzle diameter, inner nozzle outstretched distance, and inner nozzle diameter. The centerline airflow velocity, turbulence intensity, and velocity distribution of the solution blowing were analyzed using the numerical simulation method. The results showed that the outer nozzle diameter had the greatest influence on the air velocity and turbulence intensity. The airflow velocity increased and the turbulence intensity decreased with the increase of the outer nozzle diameter. The inner nozzle outstretched distance only affected the airflow convergence point and had less effect on the airflow velocity and turbulence intensity. The captured trajectory of the polymer jet initially shows a straight or slightly curved development that eventually diverges from the airflow field. With an increasing distance, dispersed fibers exhibit instability, including loop formation, bonding, and separation. The experimental observation of fiber morphology in the solution-blowing web further verified the instability during the fiber movement.

Spiral Structured Cellulose Acetate Membrane Fabricated by One-Step Electrospinning Technique with High Water Permeation Flux

A functionally graded membrane (FGM) with a special spiral-structured cellulose acetate (CA) membrane was prepared by electrospinning under different collection distances. The membrane morphology was analyzed by scanning electron microscopy (SEM). FESEM images revealed that the high concentration shows the formation of fibers with an irregular diameter, with a large diameter distribution range. The fiber collected at a short distance of 10 cm experiences the strong electrostatic force, resulting in the short flight time for the polymer jet. This causes the bending instability of the polymer jet forming the comparatively thick fiber diameters, whereas the fiber collected at 15 cm shows the presence of a smooth, homogeneous diameter. Furthermore, the water flux of the membrane was determined using 50 mL of Amicon stirred cells. The fiber collected at different distances showed diameter variation, which is used to design a special spiral structure on the membrane by auto-moving the collector between the fixed distances of 10–20 cm. This technique will reveal a new approach for the fabrication of a special spiral structure on the nanofibrous membrane for different biomedical applications from different polymers. Meanwhile, the fabricated FGM with a special spiral-structure CA membrane demonstrates high water permeation flux.

The Role of 3D Printing Technologies in Soft Grippers.

Soft grippers are essential for precise and gentle handling of delicate, fragile, and easy-to-break objects, such as glassware, electronic components, food items, and biological samples, without causing any damage or deformation. This is especially important in industries such as healthcare, manufacturing, agriculture, food handling, and biomedical, where accuracy, safety, and preservation of the objects being handled are critical. This article reviews the use of 3D printing technologies in soft grippers, including those made of functional materials, nonfunctional materials, and those with sensors. 3D printing processes that can be used to fabricate each class of soft grippers are discussed. Available 3D printing technologies that are often used in soft grippers are primarily extrusion-based printing (fused deposition modeling and direct ink writing), jet-based printing (polymer jet), and immersion printing (stereolithography and digital light processing). The materials selected for fabricating soft grippers include thermoplastic polymers, UV-curable polymers, polymer gels, soft conductive composites, and hydrogels. It is conclude that 3D printing technologies revolutionize the way soft grippers are being fabricated, expanding their application domains and reducing the difficulties in customization, fabrication, and production.

Nanomembrane Approach Reuses Waste, Cleans Produced Water

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213946, “Nanomembranes From Polymeric Waste for Produced-Water Treatment,” by Anton Manakhov, Iaroslav Rybkin, and Fahd I. AlGhunaimi, Saudi Aramco, et al. The paper has not been peer reviewed. _ In the oil and gas sector, produced water is the most significant waste stream. Among the different materials used for water filtration, including ceramics, polymers, and carbon nanomaterials, polymeric nanofibers can be considered a unique solution that can be used as a membrane or an adsorbent. In the complete paper, the authors write that polymeric nanofibers can be prepared from polystyrene waste. Introduction The management of polystyrene trash and recycling creates a significant environmental problem. While most of this substance ends up in landfills, only a small portion of polystyrene is recycled or burned. By turning this trash into products with added value, recycling will become more appealing economically and will result in lower CO2 emissions and less chemical waste dumped on the ground. At the same time, the use of modified nanofiltration membranes for generated-water purification has been a subject of study for many researchers. The complete paper includes a review of the literature dedicated to advances in this approach. Dissolved polystyrene waste can be used as a feedstock in the electrospinning process to create nanofibrous membranes. Electrospinning is one of the more basic methods for producing nanofibers with dimensions ranging from micrometers to nanometers. Strong electrostatic forces are used to overcome the surface tension of a polymer solution or melt. These pressures produce the ejection of charged polymer jets, which dry as they approach a grounded electrode, where they are gathered as nanofibers. In this work, the nanofibrous polystyrene membranes were prepared from discarded expanded polystyrene waste. Initially, polystyrene waste was collected and dissolved in an organic solvent; then, the nanofibrous membranes were prepared by the electrospinning of nanofibers from this solution. The morphology, pore sizes, and other parameters were controlled and optimized by tuning the concentration of polystyrene, the nature of the solvent, and the spinning voltage to form uniformly sized nanofibrous membranes.

Electrospinning drafting system for polyamide 6 and polyamide 6.6 nanofiber production

Electrospinning or electrostatic spinning is a straightforward, economical and unique method to produce novel fibers with diameters in the range of 100 nm and even less. However, this process is characterized by uncontrolled and chaotic oscillation of the charged electrospinning jet, which leads to the formation of beads, beaded fibers and uneven nanofibers. This research work aims at the development of an electrospinning system to control the deposition of electrospun nanofibers of polyamide 6 (PA6) and polyamide 6.6 (PA6.6) through the use of a series of metal rings, along the charged jet path, and the addition of a secondary direct current voltage power supply connected to these metal rings, which enables greater control over the polymer jet stream. In the present work, the effects of the addition of the charged metal rings with different applied voltages and some electrospinning parameters on the morphological appearance and average size diameter of the electrospun PA6 and PA6.6 fibers are investigated. The use of the developed electrospinning system with metal rings connected to the second power supply with increasing voltages proved to be successful in obtaining thinner PA6 and PA6.6 nanofibers with a lower standard deviation and the formation of few beads.

Raman Analysis of Orientation and Crystallinity in High Tg, Low Crystallinity Electrospun Fibers.

Electrospun fibers of amorphous or low-crystallinity polymers typically exhibit a low molecular orientation that can hamper their properties and application. A key stage of the electrospinning process that could be harnessed to mitigate the loss of orientation is jet rigidification, which relates closely to the solvent evaporation rate. Here, we establish quantitative Raman methods to assess the molecular orientation and crystallinity of weakly crystalline poly(2,6-dimethyl-1,4-phenylene oxide) fibers with varying diameters. Our findings demonstrate that solvent volatility can be leveraged to modulate the orientation and crystallinity through its impact on the effective glass transition temperature (Tg,eff) of the polymer jet during the electrospinning process. Specifically, a highly volatile solvent yields a higher and more sustained orientation (median ⟨P2⟩ of 0.53 for diameters < 1.0 µm) because its fast evaporation rapidly increases Tg,eff above room temperature. This vitrification early along the jet path promotes the formation of an oriented amorphous phase and a moderate fraction of strain-induced crystals. Our data reveals that a high Tg is a crucial parameter for reaching high orientation in amorphous or low-crystallinity polymer systems.

Numerical analysis of airflow fields in new modified melt-blowing dies

Considerable research has been devoted to the optimization of die configuration to effectively reduce both fiber diameter and roping defects. While some progress has been made, the challenge of developing an improvement method for the melt-blowing die that maintains the production efficiency of the original equipment while not damaging it and without introducing unnecessary energy consumption, still persists. Herein, we report a series of new modified dies featuring gradually shrinking air slots along with an internal flow stabilizer or arc nose piece that can be obtained without damaging the original die. The simulation results indicate that the new modified die demonstrated a remarkable enhancement in various aspects. Notably, it resulted in a substantial increase of 40.61% and 11.18 K in average centerline air velocity and average air stagnation temperature, respectively, while simultaneously achieving a remarkable reduction of 49.45% in average centerline turbulence kinetic energy. In addition, our modifications yielded an impressive maximum reduction of 23.08% in fiber diameter. The simulated motion characteristics of the polymer jet demonstrated that the new modified die exhibited superior polymer jet attenuation and lower whipping amplitude. The findings of this study indicate that the new modified die, which incorporates gradually shrinking air slots along with an internal flow stabilizer or arc nose piece, shows promise for the production of melt-blown nonwovens with smaller fiber sizes and a reduced occurrence of roping defects. Future research and development will concentrate on practically implementing this technology in melt-blowing production.

One-step fabrication of soot particle-embedded fibrous membranes for solar distillation using candle burning-assisted electrospinning

Solar distillation, a promising technique for water purification and desalination, requires photothermal materials to efficiently convert solar energy into heat. In this study, a novel method is proposed wherein fresh carbonaceous (soot) particles, as a photothermal material, are embedded into electrospun fibrous membranes by burning candles (to produce soot) and electrospinning of polymer material simultaneously. The proposed method can produce several types of membranes with various particle positions (interior or exterior) in the polymer fiber. The particle positions were adjusted by changing the introduction points of particles using a polymer jet. Polymer fibers with diameters of several hundred nanometers were fabricated. Experiments revealed that the soot particle position did not influence the photothermal conversion performance of the membranes. The fabricated membrane could improve the heat localization up to 194.5% and exhibited water distillation and desalination rates as high as 1.60 and 1.55 kg m−2h−1, respectively, under 1-sun solar light irradiation. The proposed method opens a new route for the functionalization of polymer membranes.

Advancing Nanofiber Research: Assessing Nonsolvent Contributions to Structure Using Coaxial Electrospinning.

In this study, we explored the influence of molecular interactions and solvent evaporation kinetics on the formation of porous structures in electrospun nanofibers, utilizing polyacrylonitrile (PAN) and polystyrene (PS) as model polymers. The coaxial electrospinning technique was employed to control the injection of water and ethylene glycol (EG) as nonsolvents into polymer jets, demonstrating its potential as a powerful tool for manipulating phase separation processes and fabricating nanofibers with tailored properties. Our findings highlighted the critical role of intermolecular interactions between nonsolvents and polymers in governing phase separation and porous structure formation. Additionally, we observed that the size and polarity of nonsolvent molecules affected the phase separation process. Furthermore, solvent evaporation kinetics were found to significantly impact phase separation, as evidenced by less distinct porous structures when using a rapidly evaporating solvent like tetrahydrofuran (THF) instead of dimethylformamide (DMF). This work offers valuable insights into the intricate relationship between molecular interactions and solvent evaporation kinetics during electrospinning, providing guidance for researchers developing porous nanofibers with specific characteristics for various applications, including filtration, drug delivery, and tissue engineering.

On-demand heart valve manufacturing using focused rotary jet spinning

On-demand heart valve manufacturing using focused rotary jet spinning

Thermochromic Responses on Melt Electrowritten Poly(ϵ-caprolactone) Microstructures

Melt electrowriting produces complex polymeric microstructures by controlling electrified polymer jet deposition. This work explores the potential of designing poly(ϵ-caprolactone) MEW microstructures with thermochromic responses. Samples with up to 4 wt % thermochromic dye content with fibers of 20.7 ± 0.9 μm have been processed without compromising printing quality. This small amount of filler content results in the desired active response of color change at a certain temperature. A multimaterial structure combining two thermochromic dyes with different activation temperatures was also designed. Overall, the ability to include additives in the MEW process without significant disruption expands the technology applicability.

Probability of jet roping in solution blowing of multiple jets

AbstractThis study describes the development and implementation of a lab‐scale four‐needle nosepiece for solution blowing, which enabled the investigation of the roping probability of four polymer jets at different inter‐needle distances and air velocities. The roping probabilities of the four jets were compared to the corresponding roping probabilities of two jets previously established by the present group. The comparison revealed that at the relatively low air velocities (pressures), the four‐jet configuration reduces roping relative to the two‐jet case, which stems from the reduction of the end effect. However, at relatively high air velocities (pressures), turbulent pulsations in the surrounding air become more dominant than the end effect. Accordingly, the four‐jet case reveals a higher probability of roping at higher air velocities (pressures). The findings shed light on the behavior of multiple solution‐blown jets and the impact of the end effect on roping. The severity of roping in the case of four jets at diminishing inter‐needle distances and increasing air velocity was analyzed using recordings of polymer jets in flight by a high‐speed camera and scanning electron microscopy of the corresponding laydown structure.

2D and 3D Electrospinning of Nanofibrous Structures by Far-Field Jet Writing

Electrospinning offers remarkable versatility in producing superfine fibrous materials and is hence widely used in many applications such as tissue scaffolds, filters, electrolyte fuel cells, biosensors, battery electrodes, and separators. Nevertheless, it is a challenge to print pre-designed 2D/3D nanofibrous structures using electrospinning due to its inherent jet instability. Here, we report on a novel far-field jet writing technique for precisely controlling the polymer jet in nanofiber deposition, which was achieved through a combination of reducing the nozzle voltage, adjusting the electric field, and applying a set of passively focusing electrostatic lenses. By optimizing the applied voltage, the circular aperture of lenses, and the distance between the adjacent lenses, the best precision achieved using this technique was approximately 200 μm, similar to that of a conventional polymer-based 3D printer. This development makes it possible for printing 2D/3D nanofibrous structures by far-field jet writing for different applications with enhanced performance.

Physics-Informed Bayesian learning of electrohydrodynamic polymer jet printing dynamics

Calibration of highly dynamic multi-physics manufacturing processes such as electrohydrodynamics-based additive manufacturing (AM) technologies (E-jet printing) is still performed by labor-intensive trial-and-error practices. Such practices have hindered the broad adoption of these technologies, demanding a new paradigm of self-calibrating E-jet printing machines. Here we develop an end-to-end physics-informed Bayesian learning framework (GPJet) which can learn the jet process dynamics with minimum experimental cost. GPJet consists of three modules: the machine vision module, the physics-based modeling module, and the machine learning (ML) module. GPJet was tested on a virtual E-jet printing machine with in-process jet monitoring capabilities. Our results show that the Machine Vision module can extract high-fidelity jet features in real-time from video data using an automated parallelized computer vision workflow. The Machine Vision module, combined with the Physics-based modeling module, can also act as closed-loop sensory feedback to the Machine Learning module of high- and low-fidelity data. This work extends the application of intelligent AM machines to more complex working conditions while reducing cost and increasing computational efficiency.

Fiber trajectory tracking of centrifugal spinning and coupled-forces field effects on jet motion stability

High-speed centrifugal spinning holds excellent potential as a promising approach for nanofiber manufacturing due to its various raw materials, low environmental requirements, and high preparation efficiency. However, continuous jet movement and trajectory tracking on the action of gravity, centrifugal force, Coriolis force, viscous force, and air resistance remain significant challenges. Therefore, the present article has developed a polymer jet motion model based on the momentum equation, continuity equation, and constitutive equation of non-Newtonian fluid to explore the influence of spinning parameters on jet motion. Moreover, curved fiber trajectory in the centrifugal field, jet velocity distribution, and variation of air velocity around the nozzle have been simulated using the discrete phase model in terms of different angular velocities and solution concentrations. It is found that the angular velocity affects the formation of the jet trajectory. Furthermore, the solution concentration determines the attenuation of the jet velocity. Therefore, centrifugal spinning experiments have been carried out to verify the correctness of the results and theoretical analysis gained from the research. Scanning electron microscope observations show nanofibers with 6 wt% polyethylene oxide solution at 5500 rpm have better morphology and quality.

Effect of inter-needle distance on jet roping and laydown structure in solution blowing

Here, a model lab-scale solution blowing setup was developed. Experiments were carried out in a model situation of two needles at several inter-needle distances and air velocities to investigate jet roping. Polymer jets issued from two needles were employed at the inter-needle distances of L = 4.5, 4, 3.5, 3, and 2.5 mm. Polymer jet intersections and merging near the needle tip and at a distance of ∼150 mm from the needle tip and near the collector were recorded employing a high-speed camera. The laydown images captured for each inter-needle distance were analyzed using scanning electron microscopy to link the laydown morphology to roping, which stems from the polymer jet–jet intersection in flight.

Semi‐Woven Structures via Dual Nozzle Melt Electrowriting

AbstractMelt electrowriting is an additive manufacturing technique utilizing electrohydrodynamic forces to create nano‐ to micro‐scale fibrous polymer objects. It is a useful research tool but has yet to reach commercial scale‐up mainly due to the intrinsically slow nature of extruding a single polymer jet. Here the concept of dual nozzle melts electrowriting requiring no new hardware other than the nozzle is introduced. Experimental data using a dual nozzle shows the possibility of doubling throughput including the phenomenon of semi‐woven structures with fibers from one nozzle either on top or under the fiber from the other nozzle depending on programmed collector movement. The study highlights the complexity of melt electrowriting when using more than one nozzle, and provides a framework for multi‐nozzle, high‐throughput melt electrowriting.

Study on the microfiber attenuation in melt-blowing airflow field

Melt blowing (MB) is a process for producing microfiber or nanofiber using high-velocity air to attenuate the polymer jet. Compared to research on the melt-blowing airflow field analysis, the melt blown die optimization, and new materials development, little work has been done on fiber attenuation and whipping in the melt-blowing process. In this study, the airflow field distribution and turbulence fluctuation of the melt-blowing die are investigated using numerical simulation. The fiber motion process is simulated with the bead-viscoelastic element model and obtained using the high-speed camera. The underlying mechanisms leading to melt-blowing fiber attenuation have been discussed. The results show that the airflow field can be separated into three regions. The turbulent fluctuations in Regions I are related to the fiber whipping in the melt-blowing process. The fiber motion in Regions II and III are unsteady, resulting in higher fiber attenuation. Region II is the main zone of fiber attenuation where the fiber whipping increases and the drawing ratio is the largest. The fluctuation of air velocity causes fiber whipping which plays an important role in fiber attenuation. Experimental results of fiber diameter reduction and fiber motion are consistent with the simulation results.

Multiphysics modeling and experimental verification of solidification point of melt-electrospun jet

Melt electrospinning has been recognized as an attractive solvent-free process over the past few decades to alleviate the solvent-related problems generated by traditional electrospinning techniques. In melt spinning, the drawing process of molten jets occurs in the liquid phase region before the phase transformation. Besides, the insufficient chain flow in the solid phase results in the non-stretchable properties of the jet in this state. This analysis predicted the phase transition displacement in the polymer jet during the melting process using a two-dimensional non-isothermal flow model integrated with an electric field. High-speed photography was employed to collect photographs of the phase transition point of the jet to verify the simulation results. Additionally, we evaluated the diameters of fibers manufactured with various phase transition displacements induced by different applied voltages. The findings of the experiments reveal that as the applied voltage is enhanced, the freezing point of the jet becomes gradually closer to the nozzle side, and the solidification length significantly reduces, resulting in smaller fiber diameter. Moreover, the results mentioned above are consistent with the law predicted by the simulation, proving the feasibility and accuracy of the model. This work will provide potential guidance for the study of nanoscale melt fibers from the perspective of fluid phase transformation.

Self-Searching Writing of Human-Organ-Scale Three-Dimensional Topographic Scaffolds with Shape Memory by Silkworm-like Electrospun Autopilot Jet.

Bioengineered scaffolds satisfying both the physiological and anatomical considerations could potentially repair partially damaged tissues to whole organs. Although three-dimensional (3D) printing has become a popular approach in making 3D topographic scaffolds, electrospinning stands out from all other techniques for fabricating extracellular matrix mimicking fibrous scaffolds. However, its complex charge-influenced jet–field interactions and the associated random motion were hardly overcome for almost a century, thus preventing it from being a viable technique for 3D topographic scaffold construction. Herein, we constructed, for the first time, geometrically challenging 3D fibrous scaffolds using biodegradable poly(ε-caprolactone), mimicking human-organ-scale face, female breast, nipple, and vascular graft, with exceptional shape memory and free-standing features by a novel field self-searching process of autopilot polymer jet, essentially resembling the silkworm-like cocoon spinning. With a simple electrospinning setup and innovative writing strategies supported by simulation, we successfully overcame the intricate jet–field interactions while preserving high-fidelity template topographies, via excellent target recognition, with pattern features ranging from 100’s μm to 10’s cm. A 3D cell culture study ensured the anatomical compatibility of the so-made 3D scaffolds. Our approach brings the century-old electrospinning to the new list of viable 3D scaffold constructing techniques, which goes beyond applications in tissue engineering.