Application Of Electric Current Research Articles

Effects of direct current on the wetting behavior and interfacial morphology between molten Sn and Cu substrate

Abstract The effect of applying a direct electric current on the wetting behavior of molten Sn on Cu substrates at a nominal temperature of 510 K was investigated using a sessile drop method. The final stable contact angles were 37 ± 5° without employing a direct current (DC) while they decreased from 29 ± 3° to 16 ± 2° when the current increased from 2.5 A to 7.5 A. The current polarity does not have a noticeable effect on the wetting behavior but on interfacial morphology. Cross-sectional microstructure observations revealed that applying a current promoted the dissolution of the Cu substrate in molten Sn and the effect was enhanced with increasing current intensity. An unusual morphology with Cu 3 Sn being the principal phase and Cu 6 Sn 5 being the secondary phase was observed under a relatively large current intensity, particularly for the case of electrons flowing from the Cu substrate to the molten Sn side. Joule heat-induced Marangoni convection in the liquid droplet and electromigration are likely to play significant roles in determining the wettability and interfacial microstructure under the application of a direct electric current.

IS 39. Enhanced visuo-spatial and language learning with tDCS

Efficacy and effectiveness of training in conditions like chronic post-stroke aphasia or neglect, or neurodegenerative disorders like mild cognitive impairment (MCI) and Alzheimer's disease, remain moderate only. Thus, novel strategies to enhance training success and overall behavioural outcome are urgently needed. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation tool that is now being widely used in neuroscientific and clinical research in humans, modulating cortical excitability by application of weak electrical currents in the form of direct current brain polarization. In a series of studies, we assessed the use of tDCS to enhance learning in the language and the visuo-spatial domain in healthy individuals (de Vries et al., 2010; Floel et al., 2008, 2011; Meinzer et al., 2012), patients in the chronic phase after stroke (Floel et al., 2011), and patients with neurodegenerative disorders (in prep). Moreover, we evaluated the mechanisms underlying the effects using both resting state and task-related functional magnetic resonance imaging (Meinzer et al., 2012). The results of these studies indicate that tDCS may effectively enhance linguistic and visuo-spatial functions in healthy individuals and patients. Mechanisms underlying this effect may include increased connectivity of stimulated brain areas with additional major hubs of the respective functional network and more efficient processing in critical task-relevant areas.

Restoration of fatigue damage in stainless steel by high-density electric current

To investigate the effect of high-density electric current on healing of the fatigue damage, the recovery of residual plastic strain was quantitatively evaluated with the digital image correlation method. The microhardness was measured within the plastic zone at the root of notch. Furthermore, the dislocation structures before and after the application of electric current were investigated by transmission electron microscopy to further understand the mechanics of the healing effect. It was concluded that the fatigue damage was healed by a decrease in dislocation density. As a result, fatigue crack initiation was delayed by the healing of fatigue damage.

In vivo assessment of human brain oscillations during application of transcranial electric currents

Brain oscillations reflect pattern formation of cell assemblies’ activity, which is often disturbed in neurological and psychiatric diseases like depression, schizophrenia and stroke. In the neurobiological analysis and treatment of these conditions, transcranial electric currents applied to the brain proved beneficial. However, the direct effects of these currents on brain oscillations have remained an enigma because of the inability to record them simultaneously. Here we report a novel strategy that resolves this problem. We describe accurate reconstructed localization of dipolar sources and changes of brain oscillatory activity associated with motor actions in primary cortical brain regions undergoing transcranial electric stimulation. This new method allows for the first time direct measurement of the effects of non-invasive electrical brain stimulation on brain oscillatory activity and behavior.

Surface Atom Motion to Move Iron Nanocrystals through Constrictions in Carbon Nanotubes under the Action of an Electric Current

Under the application of electrical currents, metal nanocrystals inside carbon nanotubes can be bodily transported. We examine experimentally and theoretically how an iron nanocrystal can pass through a constriction in the carbon nanotube with a smaller cross-sectional area than the nanocrystal itself. Remarkably, through in situ transmission electron imaging and diffraction, we find that, while passing through a constriction, the nanocrystal remains largely solid and crystalline and the carbon nanotube is unaffected. We account for this behavior by a pattern of iron atom motion and rearrangement on the surface of the nanocrystal. The nanocrystal motion can be described with a model whose parameters are nearly independent of the nanocrystal length, area, temperature, and electromigration force magnitude. We predict that metal nanocrystals can move through complex geometries and constrictions, with implications for both nanomechanics and tunable synthesis of metal nanoparticles.

Passive electric potential CT method using piezoelectric film for identification of defects

The present authors proposed the electric potential computed tomography (CT) method for identifying defects in electric-conductive bodies from electric potential distributions observed on their surfaces under electric current application. When the piezoelectric material is pasted on a cracked body subjected to mechanical load, the electric potential distribution can be obtained due to the direct piezoelectric effect without applying the electric current. The passive electric potential CT method proposed by the present authors uses this distribution. This paper describes the fundamentals of the passive electric potential CT method, inverse analysis schemes and its applications for identification of a through-thickness crack, a surface crack, plural cracks and delamination in a layered composite material. The usefulness of the method is demonstrated.

High-Frequency TRNS Reduces BOLD Activity during Visuomotor Learning

Transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS) consist in the application of electrical current of small intensity through the scalp, able to modulate perceptual and motor learning, probably by changing brain excitability. We investigated the effects of these transcranial electrical stimulation techniques in the early and later stages of visuomotor learning, as well as associated brain activity changes using functional magnetic resonance imaging (fMRI). We applied anodal and cathodal tDCS, low-frequency and high-frequency tRNS (lf-tRNS, 0.1–100 Hz; hf-tRNS 101–640 Hz, respectively) and sham stimulation over the primary motor cortex (M1) during the first 10 minutes of a visuomotor learning paradigm and measured performance changes for 20 minutes after stimulation ceased. Functional imaging scans were acquired throughout the whole experiment. Cathodal tDCS and hf-tRNS showed a tendency to improve and lf-tRNS to hinder early learning during stimulation, an effect that remained for 20 minutes after cessation of stimulation in the late learning phase. Motor learning-related activity decreased in several regions as reported previously, however, there was no significant modulation of brain activity by tDCS. In opposition to this, hf-tRNS was associated with reduced motor task-related-activity bilaterally in the frontal cortex and precuneous, probably due to interaction with ongoing neuronal oscillations. This result highlights the potential of lf-tRNS and hf-tRNS to differentially modulate visuomotor learning and advances our knowledge on neuroplasticity induction approaches combined with functional imaging methods.

Effect of High-Density Electric Current on the Microstructure and Fatigue Crack Initiation of Stainless Steel

To investigate the effect of high-density electric current on the delay of fatigue crack initiation, the dislocation structures before and after the application of electric current were investigated by transmission electron microscopy. Dislocation density was quantitatively characterized before and after the application of electric current to further understand the mechanics of the healing effect. Atomic force microscope results showed that the slips disappeared locally and the slip height decreased on the surface of the specimens. Furthermore, the delaying effect of the crack initiation due to the application of electric current was evaluated by the fatigue crack-initiation model in which the accumulation of the dislocation density was considered. [doi:10.2320/matertrans.M2013198]

Neuromuscular electrostimulation techniques: historical aspects and current possibilities in treatment of pain and muscle waisting

Application of electricity for pain treatment dates back to thousands of years BC. The Ancient Egyptians and later the Greeks and Romans recognized that electrical fishes are capable of generating electric shocks for relief of pain. In the 18th and 19th centuries these natural producers of electricity were replaced by man-made electrical devices. This happened in following phases. The first was the application of static electrical currents (called Franklinism), which was produced by a friction generator. Christian Kratzenstein was the first to apply it medically, followed shortly by Benjamin Franklin. The second phase was Galvanism. This method applied a direct electrical current to the skin by chemical means, applied a direct and pulsed electrical current to the skin. In the third phase the electrical current was induced intermittently and in alternate directions (called Faradism). The fourth stage was the use of high frequency currents (called d'Arsonvalisation). The 19th century was the "golden age" of electrotherapy. It was used for countless dental, neurological, psychiatric and gynecological disturbances. However, at beginning of the 20th century electrotherapy fell from grace. It was dismissed as lacking a scientific basis and being used also by quacks and charlatans for unserious aims. Furthermore, the development of effective analgesic drugs decreased the interest in electricity. In the second half of the 20th century electrotherapy underwent a revival. Based on animal experiments and clinical investigations, its neurophysiological mechanisms were elucidated in more details. The pain relieving action of electricity was explained in particular by two main mechanisms: first, segmental inhibition of pain signals to the brain in the dorsal horn of the spinal cord and second, activation of the descending inhibitory pathway with enhanced release of endogenous opioids and other neurochemical compounds (serotonin, noradrenaline, gamma aminobutyric acid (GABA), acetylcholine and adenosine). The modern electrotherapy of neuromusculo- skeletal pain is based in particular on the following types: transcutaneous electrical nerve stimulation (TENS), percutaneous electrical nerve stimulation (PENS or electro-acupuncture) and spinal cord stimulation (SCS). In mild to moderate pain, TENS and PENS are effective methods, whereas SCS is very useful for therapy of refractory neuropathic or ischemic pain. In 2005, high tone external muscle stimulation (HTEMS) was introduced. In diabetic peripheral neuropathy, its analgesic action was more pronounced than TENS application. HTEMS appeared also to have value in the therapy of symptomatic peripheral neuropathy in end-stage renal disease (ESRD). Besides its pain-relieving effect, electrical stimulation is of major importance for prevention or treatment of muscle dysfunction and sarcopenia. In controlled clinical studies electrical myostimulation (EMS) has been shown to be effective against the sarcopenia of patients with chronic congestive heart disease, diabetes, chronic obstructive pulmonary disease and ESRD.

Sliding wear behavior of copper alloy impregnated C/C composites under an electrical current

The wear behavior of copper-impregnated carbon fiber reinforced carbon composites (C/C composites) was investigated using a block-on-ring type wear tester during application of a DC electrical current. Three types of C/C composite contact strip materials were tested. The wear test was carried out at a constant sliding speed of 55.6m/s with a normal load of 59N, and applied electrical currents ranging from 100 to 500A. The arc-discharging rate, which is defined as the ratio of arc-discharging time to total sliding time, ranged from 0% to 35%. We also investigated the thermal and oxidation properties of the C/C composites with the laser flash method and TG-DTA. The results of the wear experiments indicate that the wear of copper-impregnated C/C composite contact strips was proportional to the arc discharge energy, which can be calculated from measurements of contact voltage and electrical current. The C/C composite contact strips with high strength carbon fiber were more likely to wear under high arc discharge energy conditions. The C/C composites made of higher strength carbon fiber have lower thermal conductivities and were more likely to be pyrolyzed or degraded by oxidation than the C/C composite with lower strength carbon fiber. These differences are thought to contribute to the difference in the wear behavior.

In situ measurement of corrosion of type 316L stainless steel in 553 K pure water via the electrical resistance of a thin wire

A system for the in situ monitoring of corrosion depth via electrical resistance measurements was applied to study the corrosion rate of type 316L stainless steel at 553 K in pure water. Corrosion depth was measured using a 50 μm diameter wire probe mounted axially in the tube. Measurements were in good agreement with literature data for both the hydrogen water chemistry (HWC) condition and the normal water chemistry (NWC) condition. Oxide film analyses by scanning electron microscopy and laser Raman spectroscopy on the wire probe and the tube showed no effects from shape of the test specimens or the application of electric current. Corrosion kinetics was evaluated by fitting equations to the measurements. Data for the HWC condition could be fitted by a two-step logarithmic–parabolic law. A single-step logarithmic law fitted data for the NWC condition. Changes in corrosion rate by the water chemistry changes were readily detected with the technique. Corrosion depth change could be observed for the water chemistry change from the NWC condition to the HWC condition with electrochemical corrosion potential (ECP) of −0.56 V vs. standard hydrogen electrode, which is lower than the ECP that the phase of iron oxide changes from α-Fe2O3 to Fe3O4.

Improvement of biological total phosphorus release and uptake by low electrical current application in lab-scale bio-electrochemical reactors

The overall process enhancement by different electrical current application on the biological phosphorus release and uptake have been investigated. Five reactors were constructed for three experiments and activated sludge was used as inoculums. In Exp.1 by comparing the control and the bio-electrochemical reactors, it was found that the overall phosphorus removal efficiency could be enhanced at lower electrical current applications of 5mA and 10mA, but were restrained at higher than 20mA, although 20mA could be a sensitive turning point. Moreover, the electrochemical effects of the cathodic and the anodic reactions on the phosphorus release and uptake, respectively, have been further evaluated separately under an electrical current application of 10mA in Exp.2 and Exp.3, respectively. As observed, both of the biological release and uptake were improved by the cathodic reactions in the cathode reactor, but not by the anodic reactions in the anode reactor, and thus indicated that the cathodic reactions play an important role in the improvement of the biological phosphorus release and uptake.

The efficiency of electrocoagulation in treating wastewater from a dairy industry, Part I: Iron electrodes

Iron electrodes were used for electrocoagulation (EC) treatment of wastewater from a dairy plant. Electrolysis time, pH, current density and distance between electrodes were considered to assess the removal efficiency of chemical oxygen demand (COD), total solids (TS) and their fractions and turbidity. Samples were collected from the effluent of a dairy plant using a sampling methodology proportional to the flow. The treatments were applied according to design factorial of half fraction with two levels of treatments and three repetitions at the central point. The optimization of parameters for treating dairy industry effluent by electrocoagulation using iron electrodes showed that electric current application for 15 minutes, an initial sample pH close to neutral (pH 7.0) and a current density of 50 A . m−2 resulted in a significant reduction in COD by 58 %; removal of turbidity, suspended solids and volatile suspended solids by 95 %; and a final treated effluent pH of approximately 9.5. Negative consequences of the type of electrode used were the emergence of an undesirable color and an increase in the proportion of dissolved solids in the treated effluent.

Microstructural characterization of electrically failed conductive traces printed from Ag nanoparticle inks

Conductive traces printed from nanoparticle loaded silver inks failed due to the application of excessive electrical current. A non-homogeneous microstructure was observed in the vicinity of the failed region consisting of sintered particles, grains and melted particles indicating a significant amount of heat was transferred to the conductive trace, in some cases, resulting in substrate damage. A simple physical model describing the failure mechanisms is proposed.

Immediate Reduction in Sweat Secretion With Electric Current Application in Primary Palmar Hyperhidrosis

Immediate Reduction in Sweat Secretion With Electric Current Application in Primary Palmar Hyperhidrosis

Morphological and Physiological Changes Detected in Skin After Iontophoresis. An In‐vivo Model

Iontophoresis is an important issue in pharmaceutical sciences, reflected by the intense research devoted to this matter. Most of the papers published about this particular technique of delivering compounds across the skin concentrate on methodological aspects, especially those concerned with specific substances used, rather than on the intimate mechanisms involved, so the authors developed an experimental in-vivo model to approach and identify the cutaneous transduction of electrical current application to skin. Using non-invasive techniques to assess the most important functional skin variables, such as trans-epidermal water loss, skin capacitance, pH and local microflow, significant changes were clearly identified after electrical current application to the skin surface. Moreover, ultrastructural analysis on the same skin areas revealed significant features such as the transient enlargement of intercellular spaces. The data obtained with this experimental model may contribute to the understanding of the mechanisms involved in iontophoresis and thus, contribute to a better knowledge of skin permeability modulation with directly applied electrical current.

β‘ Phase Precipitation in a Cold Rolled Cu-Zn Alloy under Electric Current Pulses

β' phase precipitation in a cold rolled Cu-Zn alloy under high density electric current pulses was studied in the present work. The results showed that the precipitation of β' phase was controlled by the angle between the current direction and rolling direction. When the angle was 45º, the application of electric current could refine α phase without β' phase precipitation, while at 0º or 90º, β' phase precipitated from α phase boundaries and distributed along the rolled direction. It was proposed that the precipitation of β' phase during the application of high density electric current was determined by the electron wind force and anisotropic electrical resistivity of the grain boundaries.

Direct delivery of MIF morpholinos into the zebrafish otocyst by injection and electroporation affects inner ear development.

In recent years, electroporation has become a popular technique for in vivo transfection of DNA, RNA, and morpholinos into various tissues, including the eye, brain, and somites of zebrafish. The advantage of electroporation over other methods of genetic manipulation is that specific tissues can be targeted, both spatially and temporally, for the introduction of macromolecules by the application of electrical current. Here we describe the use of electroporation for transfecting mif and mif-like morpholinos into the tissues of the developing inner ear of the zebrafish. In past studies, mif morpholino injected into embryos at the 1- to 8-cell stage resulted in widespread morphological changes in the nervous system and eye, as well as the ear. By targeting the tissues of the inner ear at later stages in development, we can determine the primary effects of MIF in the developing inner ear, as opposed to secondary effects that may result from the influence of other tissues. By using phalloidin and acetylated tubulin staining to study the morphology of neurons, neuronal processes, and hair cells associated with the posterior macula, we were able to assess the efficacy of electroporation as a method for targeted transfection in the zebrafish inner ear. The otic vesicles of 24hpf embryos were injected with morpholinos and electroporated and were then compared to embryos that had received no treatment or had been only injected or electroporated. Embryos that were injected and electroporated showed a decrease in hair cell numbers, decreased innervation by the statoacoustic ganglion (SAG) and fewer SAG neurons compared with control groups. Our results showed that direct delivery of morpholinos into otocysts at later stages avoids the non-specific nervous system and neural crest effects of morpholinos delivered at the 1-8 cell stage. It also allows examination of effects that are directed to the inner ear and not secondary effects on the ear from primary effects on the brain, neural crest or periotic mesenchyme.

Direct Delivery of MIF Morpholinos Into the Zebrafish Otocyst by Injection and Electroporation Affects Inner Ear Development

In recent years, electroporation has become a popular technique for in vivo transfection of DNA, RNA, and morpholinos into various tissues, including the eye, brain, and somites of zebrafish. The advantage of electroporation over other methods of genetic manipulation is that specific tissues can be targeted, both spatially and temporally, for the introduction of macromolecules by the application of electrical current. Here we describe the use of electroporation for transfecting mif and mif-like morpholinos into the tissues of the developing inner ear of the zebrafish. In past studies, mif morpholino injected into embryos at the 1- to 8-cell stage resulted in widespread morphological changes in the nervous system and eye, as well as the ear. By targeting the tissues of the inner ear at later stages in development, we can determine the primary effects of MIF in the developing inner ear, as opposed to secondary effects that may result from the influence of other tissues. By using phalloidin and acetylated tubulin staining to study the morphology of neurons, neuronal processes, and hair cells associated with the posterior macula, we were able to assess the efficacy of electroporation as a method for targeted transfection in the zebrafish inner ear. The otic vesicles of 24hpf embryos were injected with morpholinos and electroporated and were then compared to embryos that had received no treatment or had been only injected or electroporated. Embryos that were injected and electroporated showed a decrease in hair cell numbers, decreased innervation by the statoacoustic ganglion (SAG) and fewer SAG neurons compared with control groups. Our results showed that direct delivery of morpholinos into otocysts at later stages avoids the non-specific nervous system and neural crest effects of morpholinos delivered at the 1-8 cell stage. It also allows examination of effects that are directed to the inner ear and not secondary effects on the ear from primary effects on the brain, neural crest or periotic mesenchyme.

Digital Fabrication of “Smart” Structures and Mechanisms - Creative Applications in Art and Design

This paper describes the design and fabrication of novel “soft” structures and mechanisms employing “smart” shapechanging materials. These structures and mechanisms incorporate shape memory alloy (SMA) micro-actuators, enabling them to exhibit lifelike movement when stimulated by the application of electric current. Fabricated by 3D printing in a soft elastomer material, their design includes internal channels into which the SMA actuators are easily mounted. Other design features allow flexibility of movement and facilitate cooling of the SMA actuators.A tentacle-like active structure is described, which incorporates an antagonistic pair of SMA micro-actuators, allowing it to exhibit two-way motion. Results are presented for the speed and range of motion of the tentacle-like structure.The paper goes on to describe a creative arts application for smart active structures and mechanisms which exploits the technologies under investigation: an interactive puppet which exhibits lifelike, expressive movement. This research in digital fabrication and smart materials has implications for the fields of interactive and robotic art and design, soft robotics and physical computing.