Abstract Self-supporting and flexible carbon fibrous mats are promising electrode materials for wearable devices. The contact resistance between adjacent fibers is still a limit for further improvement of energy storage performance.... more
Abstract Self-supporting and flexible carbon fibrous mats are promising electrode materials for wearable devices. The contact resistance between adjacent fibers is still a limit for further improvement of energy storage performance. Herein, an activated interconnected lignin-derived carbon fibrous network (AILCFN) is fabricated by electrospinning followed by heat treatment. The unique interconnected structure between fibers in AILCFN is designed by controlling the ratio of soft Kraft lignin fractions with different thermal mobility. While the interconnected fibers are benefited for the electron transport and conductive property of the carbon networks, the high specific surface area is synergistically conduced to the direct channels for the fast ion transfer. The as-prepared AILCFN-3 exhibits an excellent specific capacitance and a high rate capability (69% from the current density from 1 to 20 mA cm−2). Further, AILCFN-3 can act as the scaffold to support the electrodeposited Ni-Co-S nanosheets. The AILCFN/Ni-Co-S composite electrode displays a high specific capacity of 1140.0 C g−1 at a current density of 10 A g−1. The assembled AILCFN/Ni-Co-S//AILCFN-3 BSH exhibits a high energy density of 30.8 Wh kg−1 with a power density of 0.8 kW kg−1 and demonstrates both excellent cyclability and flexibility, attributed to the high effective specific surface area and advantageous interconnected structure. The self-powered system assembled onto a lab coat can continuously power for the electronic watch under sunlight illumination and dark environment, demonstrating the promising potential of AILCFN in future wearable electronics. This work represents a “waste into wealth” direction of conversion strategy from biomass waste lignin to value-added energy storage materials, which conversely turns different thermal property of lignin fractions to good account, and breaks through the application limits caused by the heterogeneity.
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Electronic textile systems applied to biological signal monitoring are of great interest to the healthcare industry, given the potential to provide continuous and long-term monitoring of healthy individuals and patients. Most developments... more
Electronic textile systems applied to biological signal monitoring are of great interest to the healthcare industry, given the potential to provide continuous and long-term monitoring of healthy individuals and patients. Most developments in e-textiles have focused on novel materials and systems without systematic considerations into how the hierarchical structure of fibrous assemblies may influence performance and compatibility of the materials during use. This work examines mechanisms underlying the stability and quality of textile-based electrocardiogram (ECG) electrodes used in a smart bra. Signal quality of the biometric data obtained affects feedback and user experience and may be influenced by characteristics and properties of the material. Under stationary and movement conditions, analysis of the raw ECG signal and heart rate, with respect to textile-electrode material properties have been performed. Currently, there is no standardized procedure to compare the ECG signal between electrode materials. In this work, several methods have been applied to compare differences between silver-based textile electrodes and silver/silver-chloride gel electrodes. The comparison methods serve to complement visual observations of the ECG signal acquired, as possible quantitative means to differentiate electrode materials and their performance.
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The development of electronic textiles used for wearable devices and systems for healthcare monitoring applications has experienced rapid growth in the last decade. Knowledge and understanding of the textile structural hierarchy, as well... more
The development of electronic textiles used for wearable devices and systems for healthcare monitoring applications has experienced rapid growth in the last decade. Knowledge and understanding of the textile structural hierarchy, as well as the ability to define properties from the fiber and yarn to the fabric level are crucial to the selection of materials and design and performance of wearable systems. However, few studies have approached the selection of optimal e-textile structures with respect to material, electrical, and signal performance properties of sensors used for long-term biological signal monitoring. In this work, a review of e-textile structural properties (fiber, yarn, and fabric) for electrocardiogram (ECG) electrodes is presented, along with their relationship to performance properties including electrical, material, ECG signal quality, fabric hand (sensory perception and quality), and physiological comfort. Considerations and insights into the textile fiber and yarn morphology, electrode structure, design, and construction are outlined. In addition, relevant and upcoming standards for e-textile testing and performance evaluation are summarized. This work serves to organize requirements for ECG textile electrodes into a general reference framework from a bottom-up approach, which can better guide the material selection and design of ECG textile electrodes for wearable applications.
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Research Interests: Chemistry, Structural Biology, Self Assembly, Transmission Electron Microscopy, Medicine, and 13 moreExtracellular Matrix, Osteoarthritis, Structural, Humans, Mutation, Collagen, Triple Helix, Protein Secondary Structure Prediction, Protein Conformation, Amino Acid Substitution Rates, Recombinant Proteins, Biochemistry and cell biology, and binding sites
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To ensure structural integrity and safety, in-service health monitoring techniques are employed in many engineering areas. The safety, cost and performance issues of these health and usage monitoring techniques are particularly important... more
To ensure structural integrity and safety, in-service health monitoring techniques are employed in many engineering areas. The safety, cost and performance issues of these health and usage monitoring techniques are particularly important in the aviation industry. At present monitoring techniques are primarily based on pessimistic predictions and periodic inspections, which are costly and inefficient. Smart solutions to health and usage monitoring techniques relates to systems including sensors for damage detection combined with advanced signal processing and analysis. The sensitivity of sensors to damage and the reliability of performance as well as low cost of integration are the major requirements. Electrospun polymer nanofiber (NF) materials have attracted tremendous interest in sensor applications as their sensing surface area dramatically increases with decreasing fiber diameter. The highly tunable composition and surface functionality of the NF material facilitate its versatile sensibility to a wide range of visible and invisible environmental stimulus. In this presentation, we introduce three classes of nanocomposite fibers that have potential for highly sensitive large area sensing of various stimuli. doi: 10.12783/SHM2015/272
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Chlorhexidine is the most commonly used anti-infective drug in dentistry. To treat infected void areas, a drug-loaded material that swells to fill the void and releases the drug slowly is needed. This study investigated the encapsulation... more
Chlorhexidine is the most commonly used anti-infective drug in dentistry. To treat infected void areas, a drug-loaded material that swells to fill the void and releases the drug slowly is needed. This study investigated the encapsulation and release of chlorhexidine from cellulose acetate nanofibers for use as an antibacterial treatment for dental bacterial infections by oral bacteria Streptococcus mutans and Enterococcus faecalis. This study used a commercial electrospinning machine to finely control the manufacture of thin, flexible, chlorhexidine-loaded cellulose acetate nanofiber mats with very-small-diameter fibers (measured using SEM). Water absorption was measured gravimetrically, drug release was analyzed by absorbance at 254 nm, and antibiotic effects were measured by halo analysis in agar. Slow electrospinning at lower voltage (14 kV), short target distance (14 cm), slow traverse and rotation, and syringe injection speeds with controlled humidity and temperature allowed fo...
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Visible-light-responsive graphite-embedded titanium dioxide nanofibers (G-TiO2 NFs), prepared by electrospinning and post-treatment with rhodizonic acid (RhA), show biocidal effects against E. coli and S. aureus when excited with visible... more
Visible-light-responsive graphite-embedded titanium dioxide nanofibers (G-TiO2 NFs), prepared by electrospinning and post-treatment with rhodizonic acid (RhA), show biocidal effects against E. coli and S. aureus when excited with visible light.
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This paper introduces an analytical method for the analysis and design of a dry-jet wet spinning system. The 1-D mass conservation equation is used, and velocity distribution is assumed to derive a simple relationship among various... more
This paper introduces an analytical method for the analysis and design of a dry-jet wet spinning system. The 1-D mass conservation equation is used, and velocity distribution is assumed to derive a simple relationship among various spinning parameters. The effect of spinneret mass flow rate, solution density, spinneret structure including velocity and air-gap length, and drawing velocity on the dry-jet wet spinning was simulated using the proposed analytical model. Theoretical prediction of fiber diameter is obtained, which depends upon spinning conditions, solution properties, and spinneret structure. The theoretical results were verified by comparing experimental data with the numerical solution. It was found obviously that the theoretical prediction has comparable accuracy as that by numerical computation. The analytical model can be useful for preliminary design of a spinning process for fabrication of fibers with controllable diameter by adjusting parameters in spinning conditi...
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Electrically conductive and magnetically permeable carbon nanofiber-based composites were developed using the electrospinning with subsequent heat treatment. The composite nanofiber contains a variable composition of magnetite... more
Electrically conductive and magnetically permeable carbon nanofiber-based composites were developed using the electrospinning with subsequent heat treatment. The composite nanofiber contains a variable composition of magnetite nanoparticles with two different size regimes, ranging from superparamagnetic (10–20 nm) to ferromagnetic (20–30 nm). The composite nanofibers are then characterized using Scanning/Transmission Electron Microscopy, X-Ray Diffractometry, Raman Spectroscopy, four-point probe, and a Superconducting Quantum Interference Device. Electromagnetic Interference Shielding Effectiveness of pristine carbon nanofibers as well as electromagnetic composite nanofibers are examined in the X-band frequency region. Higher degree of graphitization, electrical conductivity, and magnetic strength are obtained for nanocomposites containing larger magnetite nanoparticles (20–30 nm). A transition from superpartamagnetic to ferromagnetic characteristics is observed during nanocomposite...
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As the distinctive properties and different applications of nanofibers, the demand of nanofibers increased sharply in recently years. Bubble electrospinning is one of the most effective and industrialized methods for nanofiber production.... more
As the distinctive properties and different applications of nanofibers, the demand of nanofibers increased sharply in recently years. Bubble electrospinning is one of the most effective and industrialized methods for nanofiber production. To optimize the set-up of bubble electrospinning and improve its mass production, the dynamic properties of un-charged and charged bubbles are studied experimentally, the growth and rupture process of a bubble are also discussed in this paper.
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2008-2009 > Academic research: refereed > Refereed conference pape
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In order to understand the dynamic response of the material/structural geometry interaction in gradient composite armor systems, tbree-dimensional finite element analysis is performed to simulate the structural behavior of the... more
In order to understand the dynamic response of the material/structural geometry interaction in gradient composite armor systems, tbree-dimensional finite element analysis is performed to simulate the structural behavior of the multi-component composite armors. Ballistic resistance is studied for a developed plain woven composite plate model, with and without ceramic facing layer, for impacting velocities ranging between 10m/s-1000m/s. Materials properties and geometry effects are explored. KEYWORDS: Gradient Design ...
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Biodegradable microcapsules as novel drug delivery systems were successfully fabricated by one-step processing using an electrospray technique.
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ABSTRACT
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The main goal of this work is to develop a fabrication process and system for silver/silver chloride (Ag/AgCl)-coated yarn, as Ag/AgCl is the preferred non-polarizing material for interfacing with the body in a clinical setting when... more
The main goal of this work is to develop a fabrication process and system for silver/silver chloride (Ag/AgCl)-coated yarn, as Ag/AgCl is the preferred non-polarizing material for interfacing with the body in a clinical setting when monitoring biological signals. A roll-to-roll electrochemical system was designed and built to deposit AgCl on Ag-coated nylon 6,6 yarn in a controllable process. In particular, the movement of the yarn, voltage limit and mixing of 0.9% sodium chloride solution were held constant while the applied current was varied. The Ag-coated nylon acted as the working electrode with two counter electrodes made of platinum. The optimal Ag/AgCl yarns were then further characterized. The roll-to-roll parameters identified include the applied current of approximately 1.82 mA/cm2 for the Ag-coated nylon yarn with a voltage limit of 2.00 V while in the electrochemical chamber. In addition, the yarn had a uniform movement of 0.08 cm/s, which meant that 7 cm of yarn was in...
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Nanosilver has been studied as a valuable material for it strong antibacterial effects. In this study, we investigated the antibacterial properties of nano silver Poly-L-Lactic acid (Ag/PLLA) composite fibrous membranes. Ag/PLLA fibrous... more
Nanosilver has been studied as a valuable material for it strong antibacterial effects. In this study, we investigated the antibacterial properties of nano silver Poly-L-Lactic acid (Ag/PLLA) composite fibrous membranes. Ag/PLLA fibrous membranes were prepared with silver nanoparticles having weight ratio of silver nanoparticles to PLLA at 5% (w/w). In vitro antibacterial tests were performed usingEscherichia coli(E. coli) andStaphylococcus aureus(Staph.) to determine the antibacterial capability of the Ag/PLLA fibrous membranes. As the results suggested, Ag/PLLA fibrous membranes showed strong antibacterial properties. Thus, Ag/PLLA fibrous membrane can be used as an antibacterial scaffold for tissue engineering.
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Rechargeable lithium ion batteries (LIB), known for its light weight, high energy density, and high voltage capacity per cell, possess a great potential in heavy duty hybrid electric vehicles, aerospace, and military applications [1].... more
Rechargeable lithium ion batteries (LIB), known for its light weight, high energy density, and high voltage capacity per cell, possess a great potential in heavy duty hybrid electric vehicles, aerospace, and military applications [1]. Graphite is used in industry as a standard anode material due to its stable charge/discharge profile and a long plateau at 0.1 V vs. Li metal. However, its maximum theoretical capacity is limited to 372 mAh/g, corresponding to LiC6 structure upon Li intercalation [2-4].
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Lignin, the second most abundant biopolymer on earth, has the potential as a low cost and renewable precursor for carbon fibers. By creating lignin carbon nanofibers for lightweight structural composites for automobiles and functional... more
Lignin, the second most abundant biopolymer on earth, has the potential as a low cost and renewable precursor for carbon fibers. By creating lignin carbon nanofibers for lightweight structural composites for automobiles and functional applications as electromagnetic shields, the value of lignin will be enhanced. Under the Lignoworks Biomaterials and Chemicals Network program, we demonstrated the feasibility of producing carbon nanofibers from softwood Kraft lignin by electrospinning and heat treatment. The morphological, mechanical, and electromagnetic properties of the lignin carbon nanofiber were characterized. Results showed 10 times increase in strength for the lignin random nanofiber mats after carbonization. Alignment of fibers further improved the mechanical strength. By doping the lignin polymer with carbon nanotubes and functional nanoparticles such as magnetite, we demonstrated the feasibility of translating the strength and electromagnetic function respectively to the lig...
The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were... more
The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the residual strength of the samples that survived millions of cycles was tested. The cross-section of the 3D braided specimens was observed after fatigue loading. It was found that the static and fatigue properties of low angle 3D braided behaved better than longitudinally reinforced 3D braided composites. For failure behavior, pure braids contain damage better and show less damage area than the braids with longitudinal yarns under fatigue loading. More cracks occurred in the 3D braided specimen with axial yarn cross-section along the longitudinal and transverse direction.
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Carbon nanofiber (CNF) made of inexpensive and bio-renewable raw materials can provide a pathway to lowering manufacturing cost of CNFs for structural composite applications. In this study, lignin nanofiber (LNF) mats were fabricated by... more
Carbon nanofiber (CNF) made of inexpensive and bio-renewable raw materials can provide a pathway to lowering manufacturing cost of CNFs for structural composite applications. In this study, lignin nanofiber (LNF) mats were fabricated by electrospinning of a blend solution of polyacrylonitrile (PAN), lignin, and 1 weight percent (wt.%) of polyethylene oxide (PEO) in N, N-dimethylformamide (DMF). The LNFs were then subjected to heat treatment processes including thermostabilization at 240 ◦ C and subsequent carbonization at 1000 ◦ C. The effects of the PAN/lignin mass ratio and the heating rate of thermostabilization on the fiber morphology, fiber diameter, and mechanical properties of the CNF mats were systematically investigated. The scanning electron microscopy (SEM) images showed that as the lignin content in the precursor decreased, the diameter of the as-spun LNFs increased. However, the diameter, surface, and structure of the CNFs did not change significantly. The diameter of C...
A new braiding mechanism capable of fabricating complex shaped two-dimensional and three-dimensional composite structures, as well as the structural geometry of this novel 3-D braid, is introduced in this paper. This new 3-D braiding... more
A new braiding mechanism capable of fabricating complex shaped two-dimensional and three-dimensional composite structures, as well as the structural geometry of this novel 3-D braid, is introduced in this paper. This new 3-D braiding process is based on a hexagonal principle and may lead to a new family of complex fiber architectures particularly for medical and a broad range of structural composite applications.
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Blending lignin as the second most abundant polymer in nature with nanostructured compounds such as dendritic polymers will not only add value to lignin, but also increase its application in various fields. In this study, softwood Kraft... more
Blending lignin as the second most abundant polymer in nature with nanostructured compounds such as dendritic polymers will not only add value to lignin, but also increase its application in various fields. In this study, softwood Kraft lignin/polyamidoamine dendritic polymer (PAMAM) blends were fabricated by solution electrospinning method to produce bead-free nanofiber mats. The mats were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), zeta potential, and thermogravimetry analysis (TGA). The chemical intermolecular interactions between lignin functional groups and abundant amino groups in PAMAM were investigated by FTIR and viscosity measurement. These interactions enhanced the mechanical and thermal characteristics of lignin/PAMAM mats, providing further potential applications at industry level.