TY - JOUR TI - Importance of Dipole Orientation in Electrostatic Aerosol Filtration AU - Kumar, A. AU - Gautam, S. AU - Atri, S. AU - Tafreshi, H. V. AU - Pourdeyhimi, B. T2 - LANGMUIR AB - Electrostatic charge is a major part of modern-day aerosol filtration media (e.g., N95 respirators and surgical facemasks) that has remained poorly understood due to its complicated physics. As such, charging a fibrous material has relied on empiricism in dire need of a mathematical foundation to further advance product design and optimization. In this concern, we have conducted a series of numerical simulations to improve our understanding of how an electrostatically charged fiber captures airborne particles and to quantify how the fiber’s dipole orientation impacts its capture efficiency. Special attention was paid to the role of Coulomb and dielectrophoretic forces in the capture of particles of different charge polarities (e.g., particles having a Boltzmann charge distribution). Simulation results were compared with the predictions of the popular empirical correlations from the literature and discussed in detail. Predictions of the empirical correlations better agreed with the simulation results obtained for fibers with a dipole perpendicular to the flow direction rather than for fibers with a dipole parallel to the flow. This indicates that such empirical correlations are more suitable for filters charged via contact electrification (friction charging), where the dipoles are mostly perpendicular to the flow direction, and less suitable for corona-charged media, where the fiber dipoles are generally parallel to the flow direction. DA - 2023/11/29/ PY - 2023/11/29/ DO - 10.1021/acs.langmuir.3c02016 VL - 39 IS - 49 SP - 17653-17663 SN - 1520-5827 ER - TY - JOUR TI - Algorithm to determine local basis weight of random fibrous networks with X-ray microtomography and SEM images AU - Hewavidana, Yasasween AU - Balci, Mehmet AU - Gleadall, Andrew AU - Pourdeyhimi, Behnam AU - Silberschmidt, Vadim AU - Demirci, Emrah T2 - TEXTILE RESEARCH JOURNAL AB - Analysis of the basis weight for random fibrous networks is important to understand their microstructure, properties and performance. Two-dimensional microscopical images show in-plane fibers without giving any information on their distribution in three dimensions. This research introduces a fully parametric algorithm for computing the local basis weight of random fibrous networks using three-dimensional images because out-of-plane fiber orientation is important, especially for high-density or thick networks. Voxel models of real nonwoven webs were generated by an X-ray micro-computed tomography system. The developed algorithm could accurately estimate a local basis weight value for random fibrous networks produced with various manufacturing parameters. Numerical results computed with the developed method were compared with those obtained with a physical weight measurement technique. The algorithm was tested and validated for various nonwoven fabrics with different densities. It was observed that the developed method can be used to examine and/or compare the basis weight of a wide range of random fibrous networks. In addition, it can be used to predict the basis weight for fabrics, especially in a new product development process. DA - 2023/12/23/ PY - 2023/12/23/ DO - 10.1177/00405175231214491 VL - 12 SP - SN - 1746-7748 KW - Basis weight KW - fibrous structure KW - nonwovens KW - parametric algorithm KW - X-ray micro-CT ER - TY - JOUR TI - Freestanding Carbon Nanofibers Derived from Biopolymer (Kraft Lignin) as Ultra-Microporous Electrodes for Supercapacitors AU - Dias, Yasmin J. AU - Silva, Vinicius D. AU - Pourdeyhimi, Behnam AU - Medeiros, Eliton S. AU - Yarin, Alexander L. AU - Kumagai, Seiji T2 - BATTERIES-BASEL AB - Lignin-derived carbon nanofibers (LCNFs) formed via the solution blowing of a biopolymer are developed here as a promising replacement for polyacrylonitrile (PAN)-derived carbon nanofibers (PCNFs) formed via electrospinning for such applications as supercapacitor (SC) electrodes. Accordingly, it is demonstrated here that a biopolymer (kraft lignin, which is, essentially, a waste material) can substitute a petroleum-derived polymer (PAN). Moreover, this can be achieved using a much faster and safer fiber-forming method. The present work employs the solution blowing of lignin-derived nonwovens and their carbonization to form electrode materials. These materials are characterized and explored as the electrodes in supercapacitor prototypes. Given the porosity importance of carbon fibers in SC applications, N2 gas adsorption tests were performed for characterization. LCNFs revealed the specific surface area (SSA) and capacitance values as high as 1726 m2/g and 11.95 F/g, which are about one-half of those for PCNFs, 3624 m2/g and 25.5 F/g, respectively. The capacitance values of LCNFs are comparable with those reported in the literature, but the SSA observed here is much higher. Moreover, no further post-carbonization activation steps were performed here in comparison with those materials reported in the literature. It was also found here that fiber pre-oxidation in air prior to carbonization and the addition of zinc chloride affect the SSA and capacitance values of both LCNFs and PCNFs. The electrochemical tests of the SCs prototypes were used to evaluate their capacitance at different charging rates, voltage windows, and the number of cycles. The capacitance of PCNFs decreased by about 47% during fast charging, while the capacitance of LCNFs improved during fast charging, bringing them to the level of only 21% below that of PCNFs. These changes were correlated with the packing density of the electrodes. It should be emphasized that LCNFs revealed a much higher mass yield, which was 4–5 times higher than that of PCNFs. LCNFs also possess a higher packing density, a lower price, and cause a significantly lower environmental impact than PCNFs. The best cell supercapacitor delivered a maximum specific energy of 1.77 Wh/kg and a maximum specific power of 156 kW/kg, surpassing conventional electrochemical supercapacitors. Remarkably, it retained 95.2% of its initial capacitance after 10,000 GCD cycles at a current density of 0.25 A/g, indicating robust stability. Accordingly, kraft lignin, a bio-waste material, holds great promise as a raw material for supercapacitor electrodes. DA - 2023/12// PY - 2023/12// DO - 10.3390/batteries9120566 VL - 9 IS - 12 SP - SN - 2313-0105 KW - kraft lignin KW - carbon nanofibers KW - ultra-microporous carbons KW - BET KW - supercapacitors KW - electrodes ER - TY - JOUR TI - Patterning of a High Surface Area Liquid Metal-Carbon Composite Film Using Laser Processing AU - Frey, Ethan J. AU - Im, Sooik AU - Bachmann, Adam L. AU - Genzer, Jan AU - Dickey, Michael D. T2 - ADVANCED FUNCTIONAL MATERIALS AB - Abstract Liquid metal is a compelling material for making soft and stretchable devices due to its high electrical conductivity and extreme stretchability. One way to pattern liquid metal is to nebulize it into small droplets, spray it onto a surface as a film, and then use a laser to “sinter” it into circuit patterns. Here, it is shown that including poly(amic acid) in the spray‐deposited film has multiple benefits: it (1) allows the unsintered regions to be removed easily, (2) lowers the power required for sintering, (3) converts to carbon upon exposure to create a carbon‐metal composite, and (4) increases the surface area of the film by 2632% compared to bulk EGaIn. The conductive liquid metal‐carbon circuits can also be transferred to a soft substrate to produce stretchable conductors. The circuits slightly increase in conductivity up to ≈30% strain and then decrease such that by 100% strain, the resistance is only ≈1.02 times its initial resistance. Lastly, the film is highly reactive with water molecules in the air, increasing in resistance over time in humid conditions. The high reactivity and surface area of the film indicate potential applications in batteries, catalysts, and capacitors. Meanwhile, the facile patterning indicates potential applications in soft circuits. DA - 2023/9/22/ PY - 2023/9/22/ DO - 10.1002/adfm.202308574 SP - SN - 1616-3028 KW - eutectic gallium-indium KW - high surface area electrodes KW - laser sintering KW - laser-induced carbonization KW - liquid metal particles KW - poly(amic acid) KW - strain-invariant resistance ER - TY - JOUR TI - Enhanced Triboelectric Charge Stability by Air-Stable Radicals AU - Im, Sooik AU - Frey, Ethan AU - Lacks, Daniel J. AU - Genzer, Jan AU - Dickey, Michael D. T2 - ADVANCED SCIENCE AB - This paper demonstrates that air-stable radicals enhance the stability of triboelectric charge on surfaces. While charge on surfaces is often undesirable (e.g., static discharge), improved charge retention can benefit specific applications such as air filtration. Here, it is shown that self-assembled monolayers (SAMs) containing air-stable radicals, 2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO), hold the charge longer than those without TEMPO. Charging and retention are monitored by Kelvin Probe Force Microscopy (KPFM) as a function of time. Without the radicals on the surface, charge retention increases with the water contact angle (hydrophobicity), consistent with the understanding that surface water molecules can accelerate charge dissipation. Yet, the most prolonged charge retention is observed in surfaces treated with TEMPO, which are more hydrophilic than untreated control surfaces. The charge retention decreases with reducing radical density by etching the TEMPO-silane with tetrabutylammonium fluoride (TBAF) or scavenging the radicals with ascorbic acid. These results suggest a pathway toward increasing the lifetime of triboelectric charges, which may enhance air filtration, improve tribocharging for patterning charges on surfaces, or boost triboelectric energy harvesting. DA - 2023/9/7/ PY - 2023/9/7/ DO - 10.1002/advs.202304459 SP - SN - 2198-3844 KW - air-stable radicals KW - charge retention KW - kelvin probe force microscopy (KPFM) KW - self-assembled monolayer (SAM) KW - triboelectric charge ER - TY - JOUR TI - Tuning Interfacial Adhesion in Polyester/Polyamide Systems AU - Machikiti, Zvikomborero AU - Pourdeyhimi, Behnam AU - Genzer, Jan AU - Efimenko, Kirill T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - Polymer–polymer adhesion is critical in polymer processing and application areas where lamination, welding, composites, blending, and coextrusion are involved. Polyethylene terephthalate/polyamide (PET/PA) pairs are widely used to produce bicomponent fibers. The strong adhesion due to the formation of chemical bonds in the interfacial region limits post-production fiber processing. The adhesion strength in the PET/PA systems showed that PET/PA66 had the highest adhesion energy, followed by PET/PA6, PET/PA11, and PET/PA12 for all processing conditions. We developed a method that enables adhesion control by introducing a poly(octadecene-alt-maleic anhydride) (POMA) alternating copolymer by either direct interfacial modification or addition into the PET phase. Upon POMA introduction to the system, the reduction in interfacial adhesion strength between PET and polyamides is observed. We established the relationship between adhesion strengths in PET/polyamide systems, processing conditions, and concentration of the POMA modifier. DA - 2023/7/31/ PY - 2023/7/31/ DO - 10.1021/acs.iecr.3c01517 VL - 7 SP - SN - 1520-5045 ER - TY - JOUR TI - Macroscale simulation of particle loading in electrostatically charged filters AU - Gautam, S. AU - Saleh, A. M. AU - Tafreshi, H. V. AU - Radney, J. G. AU - Pourdeyhimi, B. T2 - JOURNAL OF AEROSOL SCIENCE AB - Existing studies have shown that particle collection efficiency of a charged filter tends to decrease with particle loading to a certain extent, then increase with further loading. This contrasts with pressure drop which monotonically increases with particle loading. This trend in particle collection efficiency is due to a variety of factors including, but not limited to, neutralization and aerodynamic shielding of the fibers' electrostatic field. The current paper presents a semi-empirical macroscale simulation method to predict the instantaneous pressure drop and particle collection efficiency of an electrostatically charged filter during the early stages of particle loading. The simulations were performed by using ANSYS software enhanced with a series of in-house subroutines. The simulation results are compared with experimental data (for calibration and validation) obtained from testing a bipolarly-charged (55 μC m−2) polypropylene filter exposed to different levels of nanoparticle loadings. The filter media was loaded (both experimentally and computationally) with polydisperse NaCl nanoparticles (count median diameter of 75 nm) having charge values of ±1e. The loaded media were then tested (experimentally and computationally) with NaCl nanoparticles spanning 10 nm–500 nm in electrical mobility diameter (from TSI 3160 filter tester) having a Fuchs charge distribution. In addition, a high-porosity conditional factor was developed for the Kozeny-Carman permeability equation to expand its application to the case of nanoparticle deposits, where the dendrites’ porosity is very high, and aerodynamic slip is expected to occur. DA - 2023/9// PY - 2023/9// DO - 10.1016/j.jaerosci.2023.106212 VL - 173 SP - SN - 1879-1964 ER - TY - JOUR TI - Carbon molecular-sieve membranes developed from a Troger's base polymer and possessing superior gas-separation performance AU - Dai, Zhongde AU - Guo, Hongfang AU - Deng, Jing AU - Deng, Liyuan AU - Yan, Jiaqi AU - Spontak, Richard J. T2 - JOURNAL OF MEMBRANE SCIENCE AB - Carbon molecular-sieve membranes possess tremendous practical advantages over unary polymer membranes by providing high gas-separation performance levels, coupled with excellent mechanical and chemical stability. Improving their overall effectiveness greatly expands the competitiveness of this class of membranes. In the present study, carbon membranes are fabricated from a Tröger’s base polymer as the precursor. By optimizing the carbonization conditions, the gas-separation performance of the resultant membranes are significantly enhanced. Under optimized conditions, a H2 permeability of up to 1135 Barrer is achieved, with a corresponding H2/CH4 selectivity of 1170 and a CO2/CH4 selectivity of 238. While increasing the operating temperature slightly reduces the selectivity, it still remains in the high-separation region. Overall, the measured separation performance levels for H2-related separations, i.e., H2/CH4, H2/N2 and H2/CO2, all substantially exceed the Robeson upper bound. Moreover, the CO2/CH4 separation efficacy also lies above the 2019 upper bound, indicating that the carbon membranes developed in the present work are versatile and promising for many different gas-separation applications. DA - 2023/8/15/ PY - 2023/8/15/ DO - 10.1016/j.memsci.2023.121731 VL - 680 SP - SN - 1873-3123 ER - TY - JOUR TI - Advances in high-throughput, high-capacity nonwoven membranes for chromatography in downstream processing: A review AU - Lavoie, Joseph AU - Fan, Jinxin AU - Pourdeyhimi, Behnam AU - Boi, Cristiana AU - Carbonell, Ruben G. T2 - BIOTECHNOLOGY AND BIOENGINEERING AB - Nonwoven membranes are highly engineered fibrous materials that can be manufactured on a large scale from a wide range of different polymers, and their surfaces can be modified using a large variety of different chemistries and ligands. The fiber diameters, surface areas, pore sizes, total porosities, and thicknesses of the nonwoven mats can be carefully controlled, providing many opportunities for creative approaches for the development of novel membranes with unique properties to meet the needs of the future of downstream processing. Fibrous membranes are already finding use in ultrafiltration, microfiltration, depth filtration, and, more recently, in membrane chromatography for product capture and impurity removal. This article summarizes the various methods of manufacturing nonwoven fabrics, and the many methods available for the modification of the fiber surfaces. It also reviews recent studies focused on the use of nonwoven fabric devices in membrane chromatography and provides some perspectives on the challenges that need to be overcome to increase binding capacities, decrease residence times, and reduce pressure drops so that eventually they can replace resin column chromatography in downstream process operations. DA - 2023/5/31/ PY - 2023/5/31/ DO - 10.1002/bit.28457 VL - 5 SP - SN - 1097-0290 KW - downstream purification KW - fibrous systems KW - membrane adsorbers KW - membrane chromatography KW - nonwovens KW - product capture and polishing ER - TY - JOUR TI - Probability of jet roping in solution blowing of multiple jets AU - Balakrishnan, Vinod Kumar AU - Pourdeyhimi, Behnam AU - Yarin, Alexander L. T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract This 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. DA - 2023/5/12/ PY - 2023/5/12/ DO - 10.1002/app.54086 VL - 5 SP - SN - 1097-4628 UR - https://doi.org/10.1002/app.54086 KW - applied polymer science KW - fiber entanglements KW - jet roping KW - jet-jet interactions KW - nonwovens KW - solution-blowing ER - TY - JOUR TI - Macroscale modeling of electrostatically charged facemasks AU - Jamali, M. AU - Atri, S. AU - Gautam, S. AU - Saleh, A. M. AU - Tafreshi, H. V. AU - Pourdeyhimi, B. T2 - AEROSOL SCIENCE AND TECHNOLOGY AB - In this study, the instantaneous collection efficiency and pressure drop of an N95 facemask is numerically simulated in a setting similar (but not identical) to that used by NIOSH to certify N95 respirators. More specifically, a CPU-friendly macroscale model is developed, for the first time, to simulate the performance of an electrostatically-charged facemask when the mask is clean and when it is loaded with neutral or neutralized nanoparticles. The simulations were performed using ANSYS software enhanced with in-house subroutines, and they were calibrated using the experimental data reported in the literature for the initial efficiency of N95 masks. In addition, a correction factor was developed for the Kozeny-Carman permeability equation to expand its application to the case of nanoparticle-deposits, where the dendrites porosity is very high and the aerodynamic slip is expected to occur. DA - 2023/4/19/ PY - 2023/4/19/ DO - 10.1080/02786826.2023.2203188 VL - 4 SP - SN - 1521-7388 KW - Se-Jin Yook ER - TY - JOUR TI - Liquid Metal Coated Textiles with Autonomous Electrical Healing and Antibacterial Properties AU - Yang, Jiayi AU - Nithyanandam, Praneshnandan AU - Kanetkar, Shreyas AU - Kwon, Ki Yoon AU - Ma, Jinwoo AU - Im, Sooik AU - Oh, Ji-Hyun AU - Shamsi, Mohammad AU - Wilkins, Mike AU - Daniele, Michael AU - Kim, Tae-il AU - Nguyen, Huu Ngoc AU - Truong, Vi Khanh AU - Dickey, Michael D. T2 - ADVANCED MATERIALS TECHNOLOGIES AB - Abstract Conductive textiles are promising for human–machine interfaces and wearable electronics. A simple way to create conductive textiles by coating fabric with liquid metal (LM) particles is reported. The coating process involves dip‐coating the fabric into a suspension of LM particles at room temperature. Despite being coated uniformly after drying, the textiles remain electrically insulating due to the native oxide that forms on the LM particles. Yet, they can be rendered conductive by compressing the textile to rupture the oxide and thereby percolate the particles. Thus, compressing the textile with a patterned mold can pattern conductive circuits on the textile. The electrical conductivity of these circuits increases by coating more particles on the textile. Notably, the conductive patterns autonomously heal when cut by forming new conductive paths along the edge of the cut. The textiles prove to be useful as circuit interconnects, Joule heaters, and flexible electrodes to measure ECG signals. Further, the LM‐coated textiles provide antimicrobial protection against Pseudomonas aeruginosa and Staphylococcus aureus . Such simple coatings provide a route to convert otherwise insulating textiles into electrical circuits with the ability to autonomously heal and provide antimicrobial properties. DA - 2023/4/2/ PY - 2023/4/2/ DO - 10.1002/admt.202202183 SP - SN - 2365-709X KW - gallium KW - mechanical sintering KW - breathable e-textile KW - healing KW - wearable electronics KW - antibacteria ER - TY - JOUR TI - Assessing Crimp of Fibres in Random Networks with 3D Imaging AU - Hewavidana, Yasasween AU - Balci, Mehmet N. N. AU - Gleadall, Andrew AU - Pourdeyhimi, Behnam AU - Silberschmidt, Vadim V. V. AU - Demirci, Emrah T2 - POLYMERS AB - The analysis of fibrous structures using micro-computer tomography (µCT) is becoming more important as it provides an opportunity to characterise the mechanical properties and performance of materials. This study is the first attempt to provide computations of fibre crimp for various random fibrous networks (RFNs) based on µCT data. A parametric algorithm was developed to compute fibre crimp in fibres in a virtual domain. It was successfully tested for six different X-ray µCT models of nonwoven fabrics. Computations showed that nonwoven fabrics with crimped fibres exhibited higher crimp levels than those with non-crimped fibres, as expected. However, with the increased fabric density of the non-crimped nonwovens, fibres tended to be more crimped. Additionally, the projected fibre crimp was computed for all three major 2D planes, and the obtained results were statistically analysed. Initially, the algorithm was tested for a small-size, nonwoven model containing only four fibres. The fraction of nearly straight fibres was computed for both crimped and non-crimped fabrics. The mean value of the fibre crimp demonstrated that fibre segments between intersections were almost straight. However, it was observed that there were no perfectly straight fibres in the analysed RFNs. This study is applicable to approach employing a finite-element analysis (FEA) and computational fluid dynamics (CFD) to model/analyse RFNs. DA - 2023/2// PY - 2023/2// DO - 10.3390/polym15041050 VL - 15 IS - 4 SP - SN - 2073-4360 KW - crimped fibre KW - fibre crimp KW - non-crimped fibre KW - nonwovens KW - parametric algorithm KW - random fibrous network KW - X-ray micro-CT ER - TY - JOUR TI - Process–Structure–Property relationship of roping in meltblown nonwovens AU - Roberts, Erin AU - Ghosh, Sujit AU - Pourdeyhimi, Behnam T2 - The Journal of The Textile Institute AB - For applications such as face masks and medical gowns, defects can pose a threat to the reliability of protective materials. Roping, the entanglement of two or more fibers in a nonwoven, can cause a decrease in pore size uniformity, filtration efficiency, and barrier properties in meltblown nonwovens. In this work, a novel measurement methodology for roping was developed utilizing SEM images, ImageJ software, and statistical analysis with R. The study analyzed 16 different meltblown nonwovens with two different die tips with a 1550 MFR polypropylene, utilizing a full factorial design with 4 factors at 2 levels. A model was developed for the mitigation of roping, and it was determined that the interactions of capillary density with air flow and air flow with die-to-collector distance (DCD) had the greatest impact on the formation of roping in meltblown nonwovens. The fundamental learnings of the effects of the process parameters on roping formation could be applied to industrial applications such as face masks to tailor the balance between filtration efficiency and air permeability. The linear model could be directly applied to applications such as HEPA (High Efficiency Particulate Air) and ULPA (Ultra Low Particulate Air) filters, for operating room and clean room filters, in which nonuniformity and loss of surface area critical to performance, and thus the mitigation of roping would be beneficial. DA - 2023/2/1/ PY - 2023/2/1/ DO - 10.1080/00405000.2022.2029277 UR - https://doi.org/10.1080/00405000.2022.2029277 KW - Nonwovens KW - roping KW - fiber bundles KW - meltblown media KW - defects ER -