Efficient Fabrication Process Research Articles

Slot-die coating of vinyl-PDMS composite membranes for alcohol perm-selective pervaporation

The use of pervaporation membranes has shown great potential in the extraction of bioethanol. However, a simple, continuous, and controllable alcohol perm-selective membrane manufacturing process is needed for practical applications. In this study, the slot-die coating technique was utilized to deposit low-viscosity vinyl-polydimethylsiloxane (vinyl-PDMS) and crosslinker onto a porous substrate. A defect-free separation layer could be created within just 20 min, which includes the membrane forming and drying process, due to the rapid hydrosilylation reaction between vinyl-PDMS and the crosslinker. Therefore, the efficient fabrication process is suitable for continuous roll-to-roll industrial production. Additionally, by optimizing the slot-die parameters, the thickness of the separation layer could be regulated from 0.4 to 15 μm. The obtained vinyl-PDMS composite membrane demonstrated a total flux of 2.8 kg m−2 h−1 and a separation factor of 10.3 for 5 wt% ethanol/water mixture at 60 °C.

Cost-Effective Fabrication of Polydimethylsiloxane (PDMS) Microfluidics for Point-of-Care Application

Microfluidics fabrication pertains to the construction of small-scale devices and systems that manipulate and control small volumes of fluids. This process involves precise engineering and manufacturing procedures aimed at designing and producing these devices, which find applications in healthcare, environmental monitoring, and chemical analysis. The present study showcases an inexpensive approach to fabricate microfluidics channels using PDMS biopolymer and soft lithography technique to achieve laminar fluid flow. Initially, a robust and adhesive mold was created by fabricating a master template using several layers of SU-8 5 and SU-8 2015 negative photoresists. Subsequently, PDMS microfluidics channels were replicated and sealed onto a glass substrate through plasma bonding treatment. High-power microscopy images and profilometer analyses demonstrated successful fabrication with minimal deviation from the initial designs and the fabricated devices (less than 0.07 mm, less than 0.6°). Both the SU-8 master template and PDMS replicate displayed average microchannel height values and surface roughness of 100 μm and 0.26 μm or lower, respectively. Additionally, the fluid test confirmed laminar flow without any leakage post plasma oxidation, indicating the completion of an efficient and cost-effective fabrication process.

A universal strategy towards the fabrication of ultra-high temperature ceramic matrix composites with outstanding mechanical properties and ablation resistance

Materials with both excellent mechanical properties and good ablation resistance are urgently needed for the applications of thermal protection system in extreme high temperature oxidizing environments. However, owing to the lack of efficient fabrication processes, the existing materials suffer from either insufficient mechanical properties or poor ablation resistance. Herein, we report a novel solid–liquid combination fabrication strategy that successfully achieves the efficient incorporation of ultra-high temperature ceramics into 3D continuous carbon fiber performs as well as rapid densification. The relative density of the green body approaches the cubic close packing of spherical particles. Using Cf/ZrB2–SiC as an example, the as-prepared composite exhibits outstanding mechanical properties with a flexural strength surpasses 600 MPa and an unprecedented work of fracture of 11,851 ± 838 J/m2, which is two orders of magnitude higher than that of the currently reported monolithic ultra-high temperature ceramics. Moreover, the high ZrB2 content endows the composites with excellent ablation resistance and is thus capable of maintaining long-term non-ablative conditions at 2500 °C. The strategy possesses remarkable universality and high design flexibility, providing a time-saving and cost-effective universal strategy for the on-demand design and fabrication of high-performance ceramic, carbon, metal, and polymer matrix composites.

PREPARATION AND JUSTIFICATION OF NANOFIBRES-LOADED MAFENIDE USING ELECTROSPINNING TECHNIQUE TO CONTROL RELEASE

Objective: The primary objective was to fabricate a novel drug delivery system capable of providing a controlled and prolonged release of antibiotics. Methods: The experimental design was formulated using Design-Expert® software (version 13), enabling systematic and efficient fabrication process optimization. The study involved the preparation of various nanofiber formulations with different ratios of the three polymers to assess their impact on drug release behavior. Mafenide, a widely used antibiotic, was chosen as the model drug for this investigation. The electrospinning process allowed for producing uniform and fine nanofibers with a high surface area, ensuring a large drug-loading capacity. The synthesized nanofibers were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to evaluate their morphology, chemical interactions, and thermal properties. The drug release kinetics of the antibiotic-loaded nanofibers were studied under different physiological conditions to assess their sustained release behavior. Results: The final nanofiber formula was successfully prepared using the electrospinning technique. The Fourier Transform Infrared Spectroscopy (FTIR) analysis was achieved to confirm the possibility of chemical interaction and bond formation between mafenide and the polymers. Present. The SEM picture of the optimized nanofiber formula showed the homogeneity and excellent entanglement of the electrospun nanofibers at a resolution of 5 µm. PVA/chitosan/HPMC and mafenide pure drug have been successfully fabricated with sufficient strength to resist swelling after absorbing wound exudate. The polymer network becomes more compact when chitosan and Hydroxypropyl Methyl Cellulose (HPMC) are combined with polyvinyl alcohol (PVA), enabling regulated swelling during solvent ingress. The polymer composite's three-dimensional network influenced how quickly the medication was released from the matrix. Sample 2's polymer network traps the medication, gradually releasing after controlled swelling, resulting in a sustained release profile compared to blank sample according to the cumulative release (%) study of mafenide loaded nanofiber and mafenide drug blank sample. Conclusion: This research successfully demonstrated the fabrication of sustained-release antibiotic nanofibers using electrospinning and three biocompatible polymers. The systematic optimization approach using Design-Expert® software proved effective in tailoring the drug release behavior of nanofibers. The developed drug delivery system holds great promise for pharmaceutical applications, particularly in improving antibiotic therapies and patient care.

Flexible, Reliable, and Lightweight Multiwalled Carbon Nanotube/Polytetrafluoroethylene Membranes with Dual-Nanofibrous Structure for Outstanding EMI Shielding and Multifunctional Applications.

In this study, lightweight, flexible, and environmentally robust dual-nanofibrous membranes made of carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) are fabricated using a novel shear-induced in situ fibrillation method for electromagnetic interference (EMI) shielding. The unique spiderweb-like network, constructed from fine CNTs and PTFE fibrils, integrates the inherent characteristics of these two materials to achieve high conductivity, superhydrophobicity, and extraordinary chemical resistance. The dual-nanofibrous membranes demonstrate a high EMI shielding effectiveness (SE) of 25.7-42.2dB at a thickness range of 100-520µm and the normalized surface-specific SE can reach up to 9931.1 dB·cm2·g-1, while maintaining reliability even under extremely harsh conditions. In addition, distinct electrothermal and photothermal conversion properties can be achieved easily. Under the stimulation of a modest electrical voltage (5V) and light power density (400mW·cm-2), the surface temperatures of the CNT/PTFE membranes can reach up to 135.1 and 147.8 °C, respectively. Moreover, the CNT/PTFE membranes exhibit swift, stable, and highly efficient thermal conversion capabilities, endowing them with self-heating and de-icing performance. These versatile, flexible, and breathable membranes, coupled with their efficient and facile fabrication process, showcase tremendous application potential in aerospace, the Internet of Things, and the fabrication of wearable electronic equipment for extreme environments.

Dielectrically Graded Photocurable Nanocomposite Coating for Achieving Enhanced Surface Insulation and Long-Term Stability

Surface functionally graded material (SFGM) exhibits novelty and effectiveness in mitigating the catastrophic surface flashover of solid insulation. However, existing SFGMs mainly rely on sophisticated, time-consuming fabrication procedures, and usually demonstrate an inadequate long-term stability. This study developed a convenient, scalable SFGM fabrication method utilizing ultraviolet light (UV) curable coating, which has simplified processing, high flashover voltage (FOV), and strong adhesion to epoxy matrix. The coating material is a mixture of photocurable acrylic resin and perfluoro-silane-treated BaTiO3 (BT) nanoparticles, whose component formula and UV-curing technique were optimized according to the rheological and photocuring properties. The insulation performance of UV-SFGM was studied by flashover tests in a compressed gaseous medium. Long-term stability was investigated by the tests of interfacial adhesion, thermal cycling resistance, and hydrofluoric acid (HF) erosion tests. Experimental results show that FOV of UV-SFGM increases by 21.94% in 0.3 MPa SF6, which is attributed to the effective reduction of the maximum electric field. As for the long-term stability, the UV-SFGM has strong adhesion to epoxy/Al2O3 substrate (cross-cut level 5B and 6.54 MPa pull-off strength), especially when surface roughening on the substrate is carried out. Moreover, good resistance to thermal cycling and HF erosion is observed in the photocurable coatings. In summary, the proposed UV-SFGM has an accurate and efficient fabrication process, high insulation performance, and good long-term stability, making it promising in industrial applications.

A Method for Designing Multi-Layer Sheet-Based Lightweight Funicular Structures

Multi-layer spatial structures usually take considerable external loads with a small material usage at all scales. Polyhedral graphic statics (PGS) provides a method to design multi-layer funicular polyhedral structures, and the structural forms are usually materialized as space frames. Our previous research shows that the intrinsic planarity of the polyhedral geometries can be harnessed for efficient fabrication and construction processes using flat-sheet materials. Sheet-based structures are advantageous over conventional space frame systems because sheets can provide more load paths and constrain the kinematic degrees of freedom of the nodes. Therefore, they are more capable of taking a wider variety of load cases compared to space frames. Moreover, sheet materials can be fabricated into complex shapes using CNC milling, laser cutting, water jet cutting, and CNC bending techniques. However, not all sheets are necessary as long as the load paths are preserved and the system does not have kinematic degrees of freedom. To find an efficient set of faces that satisfies the requirements, this paper first incorporates and adapts the matrix analysis method to calculate the kinematic degrees of freedom for sheet-based structures. Then, an iterative algorithm is devised to help find a reduced set of faces with zero kinematic degrees of freedom. To attest to the advantages of this method over bar-node construction, a comparative study is carried out using finite element analysis. The results show that, with the same material usage, the sheet-based system has improved performance than the framework system under a range of loading scenarios.

Physicochemically reformed tin oxide film fabricated for self-alignment of liquid crystals

This study compressed the conventional two-step process of brush coating and orientation for liquid crystal (LC) alignment layer manufacturing into a one-step process. Surface modification and LC alignment were performed by brush coating with a tin oxide solution prepared via the solgel process at different curing temperatures. The effect of the curing temperature on atomic bonds was analyzed through x-ray photoelectron spectroscopy, the physical morphology of the film surface was characterized by scanning electron microscopy and atomic force microscopy, and the LC alignment of the brush-coated tin oxide film was verified via polarized optical microscopy and pretilt angle measurements. The shear stress generated during the brush coating process formed a partial groove structure; the resulting anisotropy aligned the LC molecules homogeneously. The brush-coated film showed excellent LC orientation properties, confirming the potential of the proposed and efficient fabrication process as a new orientation technology.

Manufacturing of Peptide Microarrays Based on Catalyst-Free Click Chemistry.

Immobilization of peptides to a solid surface is frequently an important first step before they can be probed with a variety of biological samples in a heterogeneous assay format for research and clinical diagnostic purposes. Peptides can be derivatized in many ways to subsequently covalently attach them to an activated solid surface such as, for instance, epoxy-functionalized glass slides. Here, we describe a clean, efficient, and reproducible fabrication process based on catalyst-free click chemistry compatible with the construction of low- to high-density peptide microarrays.

Uniformity Control of Laser-Induced Periodic Surface Structures

Laser-induced periodic surface structures (LIPSSs) are a universal phenomenon that can be observed on a variety of materials, including metals, semiconductors, and dielectrics, upon irradiation with ultrafast laser pulses. It has found various potential applications in the fields of optics, biologics, and mechatronics due to its efficient and flexible fabrication process and subwavelength quasi-periodic property. However, LIPSSs face the challenge of uniformity control because the formation of micro-/nanostructures induced by ultrafast laser is a complex process involving multiple interacting factors, including laser energy deposition, phase change, light scattering, and instantaneous local changes of material properties and their feedback mechanisms. Recently, there has been some significant progress regarding the control of LIPSS uniformity. In this work, we review recent experimental and methodological advances on this topic from three aspects: 1) laser-induced modified-LIPSS, 2) feedback mechanism of LIPSS formation, and 3) ultrafast laser pulse shaping. This review can stimulate further investigations into the uniformity control of LIPSSs to support and accelerate the industrial applications of uniform LIPSSs.

Direct Laser Writing of Poly(furfuryl Alcohol)/Graphene Oxide Electrodes for Electrochemical Determination of Ascorbic Acid

AbstractDue to the considerable importance of preventing and treating diseases, efficient detection methods are required to monitor levels of ascorbic acid (AA) in beverages, foods, dietary supplements, and biological fluids. In this work, an efficient, easy handling, low cost, and simple fabrication process for non‐enzymatic electrochemical sensors was fabricated through the carbonization of a graphene oxide filled biomass‐derived polymer poly(furfuryl alcohol) (PFA/GO), as sustainable alternative, using a high throughput CO2 laser‐scribing process. The laser power was found to determine the physicochemical properties of the resulting graphene‐like electrodes. As an electrochemical sensor, devices presented a detection limit of 1.0 μmol cm2 L−1 with good reproducibility towards AA oxidation. For real sample measurements, recovery rates between 97 and 113 % were found in commercial vitamin‐C tablet. Analysis of AA in synthetic sweat presented good intra‐electrode reproducibility and limit of detection of 1.3 μmol cm2 L−1.

Interdigitated Organic Sensor in Multimodal Facemask's Barrier Integrity and Wearer's Respiration Monitoring.

Facemasks are used as a personal protective equipment in medical services. They became compulsory during the recent COVID-19 pandemic at large. Their barrier effectiveness during various daily activities over time has been the subject of much debate. We propose the fabrication of an organic sensor to monitor the integrity of surgical masks to ensure individuals’ health and safety during their use. Inkjet printing of an interdigitated conducting polymer-based sensor on the inner layer of the mask proved to be an efficient and direct fabrication process to rapidly reach the end user. The sensor’s integration happens without hampering the mask functionality and preserving its original air permeability. Its resistive response to humidity accumulation allows it to monitor the mask’s wetting in use, providing a quantified way to track its barrier integrity and assist in its management. Additionally, it detects the user’s respiration rate as a capacitive response to the exhaled humidity, essential in identifying breathing difficulties or a sign of an infection. Respiration evaluations during daily activities show outstanding performance in relation to unspecific motion artifacts and breathing resolution. This e-mask yields an integrated solution for home-based individual monitoring and an advanced protective equipment for healthcare professionals.

Dendrites‐Free Lithium Metal Anode Enabled by Synergistic Surface Structural Engineering

AbstractLithium (Li) metal with high specific capacity and low redox potential is widely considered as a potential anode for lithium‐ion batteries (LIBs) with high energy density. However, the catastrophic dendrites growth, “dead Li” formation, and surface passivation hinder its practical application. Herein, a selective artificial solid electrolyte interphase (SEI) layer (Li2Sx, x = 1, 2) protection strategy is adopted, where the tip sites passivation and the uniform Li nucleation in grooves are well combined, which enables reversible Li stripping/plating with high storage capacity and robust electrode framework. The grooves derived patterned array Li with selective Li2Sx artificial SEI (LS@A‐Li) exhibit over 1800 h cycling life at 1.0 mA cm–2/1.0 mAh cm–2 and over 600 h even under 5.0 mA cm–2/10.0 mAh cm–2. The application feasibility of such LS@A‐Li is also confirmed by coupling with commercial LiFePO4 and LiNi0.5Co0.2Mn0.3O2 (NCM523) in the full batteries. This work paves way for the large‐scale application of Li metal anode in lithium‐metal batteries with a facile and efficient fabrication process.

Super-efficient drilling of metals with ultrafast non diffractive laser beams

A highly efficient drilling process is found in non-transparent metallic materials enabled by the use of non-diffractive ultrafast Bessel beams. Applied for deep drilling through a 200 μm-thick steel plate, the Bessel beam demonstrates twofold higher drilling efficiency compared to a Gaussian beam of similar fluence and spot size. Notwithstanding that surface ablation occurs with the same efficiency for both beams, the drilling booster results from a self-replication and reconstruction of the beam along the axis, driven by internal reflections within the crater at quasi-grazing incidence, bypassing potential obstacles. The mechanism is the consequence of an oblique wavevectors geometry with low angular dispersion and generates a propagation length beyond the projection range allowed by the geometry of the channel. With only the main lobe being selected by the channel entrance, side-wall reflection determines the refolding of the lobe on the axis, enhancing and replicating the beam multiple times inside the channel. The process is critically assisted by the reduction of particle shielding enabled by the intrinsic self-healing of the Bessel beam. Thus the drilling process is sustained in a way which is uniquely different from that of the conventional Gaussian beam, the latter being damped within its Rayleigh range. These mechanisms are supported and quantified by Finite Difference Time Domain calculations of the beam propagation. The results show key advantages for the quest towards efficient laser drilling and fabrication processes.

Extradosed cable‐stayed Pelješac Bridge in Croatia – Fabrication of steel box girders and on‐site installation

AbstractThe new Pelješac Bridge and access road project, which links Mainland Croatia to the Pelješac Peninsula, is the most significant social infrastructure project in Croatia under construction at present. The bridge site lies in the highly active seismic region with ground acceleration ag = 0.34g and a maximum average ten‐minute wind speed above 33.7 m/s. As a result, the execution class for the steel structure was judged to be EXC4 based on the recommended matrix in standard EN 1090‐2, which defines execution classes according to consequence class, service category, and production category. The correspondingly determined quality level was class B+, which equates to quality class B under ISO 5817 with supplementary requirements for bridge decks from EN 1090‐2. This article describes the whole fabrication process in the workshop, the long‐distance transportation and the installation on the bridge site. To satisfy such high‐quality technical requirements, the heavy steel structures were fabricated using a wide variety of mechanized equipment and automatic welding techniques. This helped to ensure a more efficient fabrication process and more consistent product quality. The length of the large side span segments was designed to suit the capabilities of the floating cranes and transit barges, thereby making on‐site installation more efficient. Against the backdrop of the global Covid‐19 pandemic, the contractor CRBC overcame seemingly unsurmountable obstacles beyond their control to successfully complete this challenging assignment in two years.

Analytical analysis and experimental validation of optical power estimation in V-grooved polymer optical fibers

In this study, analytical and experimental research of V-grooved polymer optical fibers (POFs)’ optical power loss characteristics is carried out. A simple mathematical model that can determine the optical output power and loss in the V-grooved structure depending on the groove angle and depth has been developed using geometric optic approaches. This model is used to analyze the effects of groove parameters and fiber diameter on optical output power in detail. Then, a low-cost and efficient groove fabrication process is performed, and V-grooves with 45⁰ half-angle and 200 µm groove depth are created on POFs with diameters of 1 mm, 2 mm, and 3 mm to be used in the experiment. When the effect of groove numbers ranging from 5 to 25 on the optical output power is examined, the behavior obtained from the experimental results is compatible with the analytical results. Output power can be estimated with greater than 95% accuracy for V-groove POF structures, optimizing the ratio of groove depth to fiber core radius for a specific groove angle.

Dissolving Polymer Microneedles for Transdermal Delivery of Insulin.

It’s of great significance to develop insulin-loaded dissolving microneedles (MNs) which are fabricated with various methods and materials for transdermal delivery of insulin to effectively and efficiently treat diabetes. In this work, we present a kind of FITC-insulin tip-loaded dissolving MNs fabricated with the mixture of polyvinyl alcohol (PVA) and sucrose using homemade PDMS MNs mold under vacuum conditions. The uniform appearance of MN arrays contributes to controlling the drug dosage well as required. Sufficient mechanical strength for penetrating tough stratum corneum can be obtained by vacuum frozen-drying for at least 6 h after peeling MNs off the mold. About 90% of the FITC-insulin is localized in the conical MN tips and can be released into the skin within 2 min after insertion. The in vivo insulin absorption study and hypoglycemic effect in diabetic mice demonstrate that the proposed insulin-loaded MNs can efficiently deliver the insulin to the systemic circulation and exhibit a similar effect to hypodermic injection on hypoglycemic administration. Together these results suggested that the efficient MN fabrication process proposed in this work shows great potential for mass production and practical application of drug-loaded dissolving MNs in the future.

Ionomer‐coated filtration membranes as an alternative to ion‐exchange membranes for demineralization by electrodialysis

AbstractIndustrial application of ion‐exchange membranes, the key component of many electro‐membrane processes, is often hindered due to their high cost—result of complex fabrication methods and use of highly engineered precursors. As an alternative to conventional anion‐exchange membrane (AMX), this study focuses on the fabrication of cation‐coated filtration membranes (CCFM‐Type 1 and CCFM‐Type 2) by depositing a thin layer of crosslinked branched polyethyleneimine (PEI)‐based ionomer on top of the porous substrate. The use of commodity precursors (PEI) in combination with energy efficient fabrication processes ensures a low end‐cost for CCFMs. The properties and the performances of these membranes are evaluated and compared with AMX. Though ionic conductance of both CCFMs is found to be lower than AMX, similar electrochemical behavior is observed for all three membranes. In terms of performance, the highest NaCl demineralization rate is given by CCFM‐Type 2, while whey demineralization rate for all three membranes is similar. Energy consumption during both processes is increased for CCFMs probably due to noticeably higher global resistance which the ED system reaches during the process. These promising results suggest the possible application of these cost‐effective CCFMs in electrodialysis demineralization processes as an alternative to commercial AMX at an industrial level.

An affordable and tunable continuous wrinkle micropattern for cell physical guidance study

Geometrical cues in the extracellular environment are essential for cells guiding. Conventional fabrications for well-defined microstructures are usually associated with expensive and time-consuming micro-electro-mechanical systems (MEMS), including lithography and etching. Additionally, the microstructures produced on silicon wafers are not amendable after molding, hindering the applicability. Here, we developed a low-cost and efficient fabrication process to generate highly ordered microstructures for cell culture by designing and fabricating a tunable wrinkled on biocompatible polydimethylsiloxane (PDMS) surfaces based on different mechanical properties of the biomaterials. The mechanical properties, including Young's modulus, tensile strength, and thickness ratio between the stiff and soft bilayers, can be determined by the thickness of PDMS film, curing temperature, UV exposure time, applied strain rates during the fabrication, leading to various amplitudes and wavelengths of the wrinkled topography on polymeric materials. Those wrinkled surfaces with micro-pattern are further applied to hCMEC/D cell culture, an immortalized human cerebral microvascular endothelial cell line, to induce cell proliferation and provide guidance for cell arrangement and migration. Therefore, this report sheds light on cell biology and biomedical tissue engineering by delivering an affordable and tunable fabrication process for wrinkles formations on the polymeric thin film.

Porous Anion Exchange Membrane for Effective Acid Recovery by Diffusion Dialysis

Diffusion dialysis (DD) employing anion exchange membranes (AEMs) presents an attractive opportunity for acid recovery from acidic wastewater. However, challenges exist to make highly acid permeable AEMs due to their low acid dialysis coefficient (Uacid). Here, a series of porous and highly acid permeable AEMs fabricated based on chloromethyl polyethersulfone (CMPES) porous membrane substrate with crosslinking and quaternization treatments is reported. Such porous AEMs show high Uacid because of the large free volume as well as the significantly reduced ion transport resistance relative to the dense AEMs. Compared with the commercial dense DF-120 AEM, our optimal porous AEM show simultaneous 466.7% higher Uacid and 75.7% higher acid/salt separation factor (Sacid/salt) when applied to acid recovery at the same condition. Further, considering the simple and efficient fabrication process as well as the low cost, our membranes show great prospects for practical acid recovery from industrial acidic wastewater.