Average Electrical Resistance Research Articles

Experimental Investigation into the Mechanical and Piezoresistive Sensing Properties of Recycled Carbon-Fiber-Reinforced Polymer Composites for Self-Sensing Applications.

This study investigates the mechanical and piezoresistive sensing properties of recycled carbon-fiber-reinforced polymer composites (rCFRPs) for self-sensing applications, which were prepared from recycled carbon fibers (rCFs) with fiber lengths of 6, 12, 18, and 24 mm using a vacuum infusion method. Mechanical properties of the rCFRPs were examined using uniaxial tensile tests, while sensing characteristics were examined by monitoring the in situ electrical resistance under cyclic and low fatigue loads. Longer fibers (24 mm) showed the superior tensile strength (92.6 MPa) and modulus (8.4 GPa), with improvements of 962.1% and 1061.1%, respectively. Shorter fibers (6 mm) demonstrated enhanced sensing capabilities with the highest sensitivity under low fatigue testing (1000 cycles at 10 MPa), showing an average maximum electrical resistance change rate of 0.7315% and a gauge factor of 4.5876. All the composites displayed a stable electrical response under cyclic and low fatigue loadings. These results provide insights into optimizing rCF incorporation, balancing structural integrity with self-sensing capabilities and contributing to the development of sustainable multifunctional materials.

Fabrication of Through-glass Vias (TGV) based 3D microstructures in glass substrate by a lithography-free process for MEMS applications

Fabrication of Through-glass Vias (TGV) based 3D microstructures in glass substrate by a lithography-free process is presented. Through-holes having an opening size of ∼ 300–500 µm and spiral-shaped embedded redistribution lines of ∼ 290 µm width and ∼ 50 µm depth were directly created in a 400 μm thick glass substrate by the electrochemical discharge machining. A 20 nm thick conformal seed layer was deposited by electroless nickel deposition, which can be a cost-effective alternative to vacuum-based physical vapor deposition techniques. The surface morphology of the electroless layer was characterized using an atomic force microscope and field emission scanning electron microscopy. Scotch-tape test showed a good adhesion of the seed layer with the glass substrate. Copper electrodeposition was performed to increase the thickness, after which thermal annealing was carried out to release the residual stress in the film. The adhesion of electrodeposited copper significantly improved after thermal annealing at 240 °C for 30 min. Electrodeposition is performed again to increase the thickness to the desired level. The current–voltage characterizations show good connectivity, and the average electrical resistance of a 3-turn square-shaped 3D microstructures is 2.41 Ω. Other spirals and square-shaped designs are also fabricated to prove the flexible capability of this ‘lithography-free’ technique.

Electrothermal Modeling and Analysis of Polypyrrole-Coated Wearable E-Textiles.

The inhomogeneity of the resistance of conducting polypyrrole-coated nylon–Lycra and polyester (PET) fabrics and its effects on surface temperature were investigated through a systematic experimental and numerical work including the optimization of coating conditions to determine the lowest resistivity conductive fabrics and establish a correlation between the fabrication conditions and the efficiency and uniformity of Joule heating in conductive textiles. For this purpose, the effects of plasma pre-treatment and molar concentration analysis of the dopant anthraquinone sulfonic acid (AQSA), oxidant ferric chloride, and monomer pyrrole was carried out to establish the conditions to determine the sample with the lowest electrical resistance for generating heat and model the experiments using the finite element modeling (FEM). Both PET and nylon-Lycra underwent atmospheric plasma treatment to functionalize the fabric surface to improve the binding of the polymer and obtain coatings with reduced resistance. Both fabrics were compared in terms of average electrical resistance for both plasma treated and untreated samples. The plasma treatment induced deep black coatings with lower resistance. Then, heat-generating experiments were conducted on the polypyrrole (PPy) coated fabrics with the lowest resistance using a variable power supply to study the distribution and maximum value of the temperature. The joule heating model was developed to predict the heating of the conductive fabrics via finite element analysis. The model was based on the measured electrical resistance at different zones of the coated fabrics. It was shown that, when the fabric was backed with neoprene insulation, it would heat up quicker and more evenly. The average electrical resistance of the PPy-PET sample used was 190 , and a maximum temperature reading of 43 °C was recorded. The model results exhibited good agreement with thermal camera data.

A new high entropy alloy brazing filler metal design for joining skutterudite thermoelectrics to copper

A new High Entropy Alloy (HEA) in the ZnGaCu-(AuSn) system was designed to join skutterudite thermoelectrics (CoSb2.75Sn0.05Te0.20), with a diffusion barrier of Ni applied, to Cu. Such a joint could be part of a device for thermal energy recovery within automotive exhaust systems. A rapid large-scale screening calculation technique based on Python programming has been introduced to conduct the HEA selection process, resulting in a series of alloys, which have been experimentally verified. It is demonstrated that a particular ZnGaCu-(AuSn) HEA alloy can join Ni and Cu successfully; a good joint is formed, and the average electrical contact resistance of the interfaces after joining is promising at room temperature, which shows that it has the potential to improve on the existing fillers used in such applications. The alloy design methodology used here suggests a potential efficient route to design new filler metals for a wide array of applications in which existing filler metals are not suitable.

Stem electrical properties associated with water stress conditions in olive tree

The analysis of the electrophysiological activity of plants permits a real-time information of the plant status (e.g. light availability and water stress). However, even though it is clear that the role of the electrical signals in plant is crucial, especially in processes involving the propagation of rapid signals, a systematic approach for the interpretation of the electrical patterns is still missing. In this work a multi-electrodes approach has been applied to study the electrical signals in olive trees plants subjected to three different level of water stress. In particular, by using specific water irrigation regimes, a control group, a mid/mild stressed group and a high stressed group have been monitored and subsequently subjected to a long period of prolonged drought stress. Physiological parameters and electrical activity have been continuously monitored for the whole experiment to highlight any correlation between the electric signal and the water stress. Our results showed that it has been possible to differentiate the electric signals related to drought conditions of different intensity (i.e. control, mild and high). In particular we have found that the average daily relative electrical resistance change, the opposite of the electrical conductance, is directly related to the drought stress whilst the signal variance increases during the period of main water stress. Additionally, a proposed signal classification system has been successfully able to detect the absence/presence of stress and to effectively recognize daily class samples (93 % control, 76 % mild and 80 % high). The set-up could provide a useful tool for monitoring water conditions in plants and has several potential applications for sensor and automatic system in greenhouse or field able to monitor directly the plant water status.

Embelin, a Potent Molecule for Alzheimer's Disease: A Proof of Concept From Blood-Brain Barrier Permeability, Acetylcholinesterase Inhibition and Molecular Docking Studies.

Embelin is well-known in ethnomedicine and reported to have central nervous system activities. However, there is no report on blood-brain barrier (BBB) permeability of embelin. Here the BBB permeability of embelin was evaluated using in vitro primary porcine brain endothelial cell (PBEC) model of the BBB. Embelin was also evaluated for acetylcholinesterase (AChE) inhibitory activity and docking prediction for interaction with AChE and amyloid beta (Aβ) binding sites. Embelin was found to be non-toxic to the PBECs and did not disturb the PBEC barrier function. The PBECs showed restrictive tight junctions with average transendothelial electrical resistance of 365.37 ± 113.00 Ω.cm2, for monolayers used for permeability assays. Permeability assays were conducted from apical-to-basolateral direction (blood-to-brain side). Embelin showed apparent permeability (Papp) value of 35.46 ± 20.33 × 10−6 cm/s with 85.53% recovery. In vitro AChE inhibitory assay demonstrated that embelin could inhibit the enzyme. Molecular docking study showed that embelin binds well to active site of AChE with CDOCKER interaction energy of −65.75 kcal/mol which correlates with the in vitro results. Docking of embelin with Aβ peptides also revealed the promising binding with low CDOCKER interaction energy. Thus, findings from this study indicate that embelin could be a suitable molecule to be further developed as therapeutic molecule to treat neurological disorders particularly Alzheimer's disease.

Micro-Molded Glassy Carbon Electrodes for High Throughput Dielectrophoresis

3D glassy carbon electrodes employed in dielectrophoresis (DEP) devices provide the advantages of simple and affordable fabrication, functionality at low voltage and the wider electrochemical stability of carbon in comparison to traditional metal electrodes [1]. Furthermore, the use of 3D electrodes offers high throughput of separation [2]. The state-of-the-art in the fabrication of glassy carbon micro- and nano-structures revolves around patterning and subsequent pyrolysis of organic precursors. In our previous work, we developed a computational model for high throughput sorting of stem cells using DEP [3]. Electrode dimensions in the range of hundreds of microns need to be fabricated to achieve practical throughput without compromising the cells by inducing increased shear stress. However, such dimensions are beyond the traditional operating range of SU-8 photolithography, making their fabrication challenging. On the other hand, precision machining techniques are still too bulky to enable easy and inexpensive fabrication in this scale. Here we propose the combination of 3D printed structures and Polydimethylsiloxane (PDMS) molds to shape an epoxy-based carbon precursor. The work presented here focuses on the development of reproducible carbon electrodes for application in high throughput dielectrophoretic separation. A 3D printed “inverse” mold containing an array of 1200 microns diameter cylindrical posts is fabricated to suit PDMS molding, which, in turn, is used to mold the carbon posts. Commercial grade PDMS mixed in the ratio of 10:1 was used to create molds of cylindrical posts using the standard procedure. The resulting PDMS molds ensured sufficient flexibility to facilitate easy removal of hardened materials. Plant-based epoxy, chitin, cellulose and carrageenan were tested in different mixtures as carbon precursors. Powdered chitin, cellulose and carrageenan were separately mixed into the epoxy at various ratios and introduced into the PDMS mold. Upon setting, they were removed from mold and pyrolyzed at 900oC in an inert atmosphere to yield conductive carbon. Initial results showed how bio-epoxy, which consists of a 2:1 ratio of resin to hardener, fails to retain the shape of the mold through the pyrolysis process. On the other hand, chitin, cellulose and carrageenan when formed into gel and pyrolyzed retain shape, but yield fragile structures. Hence, we combined the binding capacity of bio-epoxy with the structural integrity provided by biopolymers. A 40-80% weight by weight mixture of chitin in bio-epoxy ensured adequate concentration for a trade-off between shape retention and molding ability. This range also pyrolyzed to give cylindrical glassy carbon posts with an average electrical resistance of 7 ohms across the 4mm distance between the farthest electrodes. Pyrolysis also brought about an average diametric shrinkage of 40% in the electrodes. Ongoing work involves using this molding process for SU-8 photoresist. We hypothesize that the production of carbon micro-electrodes is a forerunner to the adoption of the same process in the manufacture of other conductive carbon components in the same size range. By characterizing further complex geometric features and identifying their suitability to this process, we aim to develop a standard to manufacture a broader range of glassy carbon micro-components. REFERENCES: [1] Martinez‐Duarte, R., Renaud, P., & Madou, M. J. (2011). A novel approach to dielectrophoresis using carbon electrodes. Electrophoresis, 32(17), 2385-2392. [2] Islam, M., Natu, R., Larraga-Martinez, M. F., & Martinez-Duarte, R. (2016). Enrichment of diluted cell populations from large sample volumes using 3D carbon-electrode dielectrophoresis. Biomicrofluidics, 10(3), 033107. [3] Natu, R., & Martinez-Duarte, R. (2016). Numerical Model of Streaming DEP for Stem Cell Sorting. Micromachines, 7(12), 217. Figure 1

Investigation of the Nanoparticle Electrical Contact Lubrication in MEMS Switches

A nanoparticle has been reported as a promising lubricant to increase the durability of microelectromechanical systems (MEMS) switches, but there remains much room for development and scientific observations. In this paper, we present the fabrication and research platform for a nanoparticle lubricated MEMS switch; we measured its characteristics and investigated the mechanisms behind it. In the measurements, gold nanoparticle lubrication demonstrated an increased average adhesion force from 16.38 to 23.68 μN by 44.51% and a decreased average electrical contact resistance from 211.20 to 49.85 mQ by 76.40%. In a hot switching mode lifetime test, the gold nanoparticle lubricated MEMS switch exhibited extension of reliability from 5.13 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> to 4.75 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cycles, which corresponds to 9.26-fold increase. We attribute this remarkable enhancement to a mechanical stress release via lateral deformation of the nanoparticle and refreshment of the contact spots owing to movement of nanoparticles.

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells.

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) models based on pBECs in mono-culture (MC), MC with astrocyte-conditioned medium (ACM), and non-contact co-culture (NCC) with astrocytes of porcine or rat origin. pBECs were isolated and cultured from fragments of capillaries from the brain cortices of domestic pigs 5-6 months old. These fragments were purified by careful removal of meninges, isolation and homogenization of grey matter, filtration, enzymatic digestion, and centrifugation. To further eliminate contaminating cells, the capillary fragments were cultured with puromycin-containing medium. When 60-95% confluent, pBECs growing from the capillary fragments were passaged to permeable membrane filter inserts and established in the models. To increase barrier tightness and BBB characteristic phenotype of pBECs, the cells were treated with the following differentiation factors: membrane permeant 8-CPT-cAMP (here abbreviated cAMP), hydrocortisone, and a phosphodiesterase inhibitor, RO-20-1724 (RO). The procedure was carried out over a period of 9-11 days, and when establishing the NCC model, the astrocytes were cultured 2-8 weeks in advance. Adherence to the described procedures in the protocol has allowed the establishment of endothelial layers with highly restricted paracellular permeability, with the NCC model showing an average transendothelial electrical resistance (TEER) of 1249 ± 80 Ω cm2, and paracellular permeability (Papp) for Lucifer Yellow of 0.90 10-6 ± 0.13 10-6 cm sec-1 (mean ± SEM, n=55). Further evaluation of this pBEC phenotype showed good expression of the tight junctional proteins claudin 5, ZO-1, occludin and adherens junction protein p120 catenin. The model presented can be used for a range of studies of the BBB in health and disease and, with the highly restrictive paracellular permeability, this model is suitable for studies of transport and intracellular trafficking.

Improved Method for the Establishment of an &lt;em&gt;In Vitro&lt;/em&gt; Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) models based on pBECs in mono-culture (MC), MC with astrocyte-conditioned medium (ACM), and non-contact co-culture (NCC) with astrocytes of porcine or rat origin. pBECs were isolated and cultured from fragments of capillaries from the brain cortices of domestic pigs 5-6 months old. These fragments were purified by careful removal of meninges, isolation and homogenization of grey matter, filtration, enzymatic digestion, and centrifugation. To further eliminate contaminating cells, the capillary fragments were cultured with puromycin-containing medium. When 60-95% confluent, pBECs growing from the capillary fragments were passaged to permeable membrane filter inserts and established in the models. To increase barrier tightness and BBB characteristic phenotype of pBECs, the cells were treated with the following differentiation factors: membrane permeant 8-CPT-cAMP (here abbreviated cAMP), hydrocortisone, and a phosphodiesterase inhibitor, RO-20-1724 (RO). The procedure was carried out over a period of 9-11 days, and when establishing the NCC model, the astrocytes were cultured 2-8 weeks in advance. Adherence to the described procedures in the protocol has allowed the establishment of endothelial layers with highly restricted paracellular permeability, with the NCC model showing an average transendothelial electrical resistance (TEER) of 1249 ± 80 Ω cm2, and paracellular permeability (Papp) for Lucifer Yellow of 0.90 10-6 ± 0.13 10-6 cm sec-1 (mean ± SEM, n=55). Further evaluation of this pBEC phenotype showed good expression of the tight junctional proteins claudin 5, ZO-1, occludin and adherens junction protein p120 catenin. The model presented can be used for a range of studies of the BBB in health and disease and, with the highly restrictive paracellular permeability, this model is suitable for studies of transport and intracellular trafficking.

Mechanically Flexible Interconnects With Contact Tip for Rematable Heterogeneous System Integration

A wafer-level, batch-fabricated, mechanically flexible interconnect (MFI) with a contact tip has been developed for rematable heterogeneous system integration. The contact tip, which exhibits a truncated-cone profile, enhances the scrubbing capability while maintaining the tip lifetime by avoiding tip plastic deformation. Electrical and mechanical characterization has been conducted on various testbeds to verify the performance of the assembled chip links with MFIs. The results indicate that a single MFI has an average electrical resistance of 103.21 $\text{m}\Omega $ and up to 1 A current carrying capability, and can be successfully assembled on nonplanar surfaces with up to 45- $\mu \text{m}$ surface variation.

Mitragynine and 7-hydroxymitragynine: In vitro blood-brain barrier permeability studies

Event Abstract Back to Event Mitragynine and 7-hydroxymitragynine: In vitro blood-brain barrier permeability studies Mahathir Mohd Uzid1*, Nur Aziah Hanapi1, Sharif Mahsufi Mansor1 and Siti Rafidah Yusof1 1 Universiti Sains Malaysia, Centre for Drug Research, Malaysia Mitragynine (MG), the major alkaloid present in the leaves of M. speciosa is reported to be responsible for opioid agonistic activity and 7-hydroxymitragynine (7-OH MG) a minor derivative, possessed much more potent opioid activity compared to mitragynine and morphine. Although the central nervous system activities of MG and 7-OH MG are widely studied, research on their blood-brain barrier (BBB) permeability is still lacking. In this study, MG and 7-OH MG permeability was studied using in vitro BBB model from primary porcine brain endothelial cells (PBECs). The PBECs showed restrictive tight junction with average transendothelial electrical resistance of 470.23 ± 21.77 Ω.cm2. Permeability assays were conducted from apical-to-basal (A-B; blood-to-brain) and basal-to-apical (B-A; brain-to-blood) directions to determine MG and 7-OH MG BBB mechanisms. Sodium fluorescein was used as parallel tight junction permeability marker. To determine interaction of MG and 7-OH MG with efflux transporters, permeability assay (A-B direction) was conducted in presence of efflux transporter inhibitor verapamil (50 µM). From the results, MG showed higher A-B permeability (Papp = 35.04 × 10-6 cm/s) compared to B-A (Papp = 21.42 × 10-6 cm/s) with efflux ratio (B-A/ A-B) of 0.61, suggesting net permeability of influx into the brain. In comparison, 7-OH MG showed lower A-B (Papp = 15.31 × 10-6 cm/s) compared to B-A (Papp = 21.31 × 10-6 cm/s) permeability with efflux ratio (B-A/ A-B) of 1.39, suggesting net permeability of efflux from the brain into the blood circulation. Presence of verapamil caused significant increase in A-B permeability of 7-OH MG (Papp = 46.62 × 10-6 cm/s), which indicates interaction of 7-OH MG with efflux transporters particularly the ATP-binding cassette transporters. This study is the first to report on mechanisms of MG and 7-OH MG BBB permeability, using primary brain endothelial cell as a model. Keywords: Blood-Brain Barrier, Nervous System, opioid, in vitro, mitragynine Conference: 14th Meeting of the Asian-Pacific Society for Neurochemistry, Kuala Lumpur, Malaysia, 27 Aug - 30 Aug, 2016. Presentation Type: Poster Presentation Session Topic: 14th Meeting of the Asian-Pacific Society for Neurochemistry Citation: Mohd Uzid M, Hanapi N, Mansor S and Yusof S (2016). Mitragynine and 7-hydroxymitragynine: In vitro blood-brain barrier permeability studies. Conference Abstract: 14th Meeting of the Asian-Pacific Society for Neurochemistry. doi: 10.3389/conf.fncel.2016.36.00145 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Aug 2016; Published Online: 11 Aug 2016. * Correspondence: Mr. Mahathir Mohd Uzid, Universiti Sains Malaysia, Centre for Drug Research, Gelugor, Pulau Pinang, Malaysia, mahathirmu@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Mahathir Mohd Uzid Nur Aziah Hanapi Sharif Mahsufi Mansor Siti Rafidah Yusof Google Mahathir Mohd Uzid Nur Aziah Hanapi Sharif Mahsufi Mansor Siti Rafidah Yusof Google Scholar Mahathir Mohd Uzid Nur Aziah Hanapi Sharif Mahsufi Mansor Siti Rafidah Yusof PubMed Mahathir Mohd Uzid Nur Aziah Hanapi Sharif Mahsufi Mansor Siti Rafidah Yusof Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Nanopatterned graphene on a polymer substrate by a direct peel-off technique.

A graphene (Gr) on a polyimide (PI) polymer film (Gr-PI film), obtained by a direct peel-off technique, is proposed and investigated. Thanks to its high transparency, electrical conductivity, mechanical strength, and chemical durability, the Gr-PI film is an ideal substrate for flexible electronic and optoelectronic devices, including transistors, light-emitting diodes, and plasmonic antennas. It is obtained using a straightforward method. After spin coating and curing a PI film on Gr previously grown on Cu, one can separate the Gr-PI film from the Cu foil thanks to the difference in the adhesive energy between the Gr-Cu and Gr-PI interfaces. The resulting Gr-PI film shows an average electrical sheet resistance ranging from 520 to 860 Ω/sq and a very high optical transmission (>90%), which have allowed the demonstration of a transparent heater. The surface morphology of the Gr-PI film follows that of the Cu foil, with the latter maintaining its surface properties and allowing in this way its reuse in subsequent chemical vapor deposition growth. The method can also be applied to patterned Gr, as is demonstrated for nanosize ribbons with a width of a few tens of nanometers.

Fabrication of through-silicon vias by supercritical CO2 emulsion-enabled nickel electroplating

Compared to the 2D plane, 3D integrated circuit (IC) structure could provide larger patterning areas by stacking the multi-planar chips, in which the electrical signals can be vertically conducted via through-silicon vias (TSVs). Thus, its advantages are lowered costs and reduced packaging space, size and weight. In this study, the TSVs used for 3D integration are fabricated and characterized. Four through holes with a diameter of 70μm on a silicon wafer are first etched by inductively coupled plasma reactive ion etch (ICP) and filled by nickel electroplating in supercritical CO2 emulsion. The chip is cut for observation and examination of the cross-sectional view of the TSVs. For hermeticity testing, a helium leaking detector was performed on all TSVs before and after the heat treatment process (heating up to 350°C). The average electrical resistance across the TSVs was measured to be 0.01Ω. Then the fabricated TSVs can be applied a maximum current of 10A continuously without burnout.

Effects of Under-layers on Surface Morphology of Sputtered Co Film

The structure, electrical resistance and surface morphology of 85 nm Co films sputtered on Cr, Co, Cu Ag and Al under-layers were studied. The average thickness and electrical resistance of the Co films were significantly altered, depending on the under-layer thickness and material. The Co film on various under-layers consisted of a Co (HCP) phase in the (101) direction. The surface morphology of the Co film was strongly dependent on the surface roughness and morphology of the under-layers. The Co film showed a maximum surface roughness of 1.69 nm and a minimum roughness of 0.720 nm over a scan area of 1 μm2 on the Ag and Cr under-layers, respectively. The grain size and distribution of the Co films were affected by the grain size and distribution of the under-layer film. The average grain size of the Co films ranged from 13.3 nm on a Co under-layer to 26.2 nm on a Cu under-layer. AFM results indicated that a small grain size on the surface area of the under-layer film gave rise to a bigger grain size of the Co film, whereas a big grain size of the under-layer film produced a smaller grain size of the Co film. The under-layer thickness and material had a secondary effect on the surface morphology of Co films, because both the thickness and material were surface morphology dependent. All results confirmed that the morphology of an under-layer film plays an important role in the surface roughness of a Co film. It can be concluded that the surface roughness and morphology of a Co film can be modified by the under-layer roughness and material.

온도 감응형 전도성 소재 특성 연구

In this paper, we measured the temperature-dependent electrical resistance of five kinds of conductive yarns for temperature-sensitive textiles. Conductive yarns for temperature-sensitive textiles are multilayered and contain copper filaments. Krifi Cu-1, 2, 3, 4, and 5 are composed of 2, 3, 4, 7, and 14 strands of the copper filament, respectively. Krifi Cu-3, 4, and 5 were covered with polyethylene terephthalate (PET) fiber for insulation. It was determined that the electrical resistance of Krifi Cu-1 and 2 increased by <TEX>$40m{\Omega}$</TEX> and <TEX>$27.1m{\Omega}$</TEX>, respectively, with each <TEX>$5^{\circ}C$</TEX> increase over the temperature range of <TEX>$30-100^{\circ}C$</TEX>. In addition, it was found that the temperature-dependent electrical resistance did not increase with increasing number of copper filaments. Temperature-sensitive textiles were manufactured by patterning two conductive yarns with high increment and determining the linearity of the temperature-dependent electrical resistance. For the temperature-sensitive textile patterned with Krifi Cu-2, the average electrical resistance was <TEX>$71.4m{\Omega}$</TEX> but the electrical resistance was not linear with temperature. The temperature-sensitive textile patterned with Krifi Cu-2 showed an average electrical resistance of <TEX>$68.6m{\Omega}$</TEX> and good linearity with temperature.

Smart conductive inks

A novel conductive ink, suitable for employment in a pressure-sensitive automatic system, was prepared and characterized via scanning electron microscopy, FTIR and differential scanning calorimetry. The ink was obtained as a composite by mixing a solution of ethyl acrylate-methyl acrylate (50/50 ratio) copolymer and carbon black and graphite into a solvent standard for acrylic polymers. The ink average electrical resistance ranges from 40 ohms/cm to 150 ohms/cm.

전기 및 유체 동시접속이 가능한 멀티칩 미소전기유체통합벤치의 설계, 제작 및 성능시험

We present the design, fabrication, and characterization of a multi-chip microelectrofluidic bench, achieving both electrical and fluidic interconnections with a simple, low-loss and low-temperature electrofluidic interconnection method. We design 4-chip microelectrofluidic bench, having three electrical pads and two fluidic I/O ports. Each device chip, having three electrical interconnections and a pair of two fluidic I/O interconnections, can be assembled to the microelectofluidic bench with electrical and fluidic interconnections. In the fluidic and electrical characterization, we measure the average pressure drop of 13.6~125.4 Pa/mm with the nonlinearity of 3.1% for the flow-rates of 10~100 μl/min in the fluidic line. The pressure drop per fluidic interconnection is measured as 0.19kPa. Experimentally, there are no significant differences in pressure drops between straight channels and elbow channels. The measured average electrical resistance is 0.26Ω/mm in the electrical line. The electrical resistance per each electrical interconnection is measured as 0.64Ω. Mechanically, the maximum pressure, where the microelectrofluidic bench endures, reaches up to 115?11kPa.

Analysis of electrical characteristics for hybrid pulsed micro-tungsten inert gas welding arc

The present paper experimentally investigates and analyses in detail the electrical characteristics of the arc for the hybrid pulsed micro-tungsten inert gas process. In particular, an average voltage–current (V–I) graph plotting approach is proposed to describe the dynamic characteristics of the hybrid arcs using the filtered voltage and current of the arc. It is shown that the average voltage and electrical resistance of the heavily hybrid pulsating (HHP) arc are lower than those of the slightly hybrid pulsating (SHP) arc, particularly during the background current stage. Furthermore, the analyses reveal that the average V–I characteristic graph for the arc forms a hysteresis loop, primarily because of the thermal inertia of the arc, during a pulse period. This closed loop is larger for the SHP arc than for the HHP arc, and shrinks longitudinally with increasing frequency and width of the current pulse. These results thus demonstrate that the HHP arc has a greater thermal inertia, particularly at higher current and pulse frequency. Experimental results show also that the mean voltage of the arc and the features of the hysteresis loop vary markedly with weld penetration in addition to pulsating frequency and pattern, and thus suggest the possibility of monitoring the hybrid pulsed weld penetration via arc sensing.

Lung epithelial cell lines in coculture with human pulmonary microvascular endothelial cells: development of an alveolo-capillary barrier in vitro

We have established a coculture system of human distal lung epithelial cells and human microvascular endothelial cells in order to study the cellular interactions of epithelium and endothelium at the alveolocapillary barrier in both pathogenesis and recovery from acute lung injury. The aim was to determine conditions for the development of functional cellular junctions and the formation of a tight epithelial barrier similar to that observed in vivo. The in vitro coculture system consisted of monolayers of human lung epithelial cell lines (A549 or NCI H441) and primary human pulmonary microvascular endothelial cells (HPMEC) on opposite sides of a permeable filter membrane. A549 failed to show sufficient differentiation with respect to formation of a tight epithelial barrier with intact cell–cell junctions. Stimulated with dexamethasone, the cocultures of NCI H441 and HPMEC established contact-inhibited differentiated monolayers, with NCI H441 showing a continuous, circumferential immunostaining of the tight junctional protein, ZO-1 and the adherens junction protein, E-cadherin. The generation of a polarized epithelial cell monolayer with typical junctional structures was confirmed by transmission electron microscopy. Dexamethasone treatment resulted in average transbilayer electrical resistance (TER) values of 500 Ω cm2 after 10–12 days of cocultivation and correlated with a reduced flux of the hydrophilic permeability marker, sodium-fluorescein. In addition, basolateral distribution of the proinflammatory cytokine tumour necrosis factor-alpha caused a significant reduction of TER-values after 24 h exposure. This decrease in TER could be re-established to control level by removal of the cytokine within 24 h. Thus, the coculture system of the NCI H441 with HPMEC should be a suitable in vitro model system to examine epithelial and endothelial interactions in the pathogenesis of acute lung injury, infectious lung diseases and toxic lung injury. In addition, it could be used to improve techniques of lung drug delivery that also requires a functional barrier.