Low-voltage Electric Fields Research Articles

Non-electroactive bacteria behave variously in AnMBR biofilm control using electric field

Electroactive bacteria are often regarded as key players responding to electric fields that are used to control biofilm development during AnMBR (anaerobic membrane bioreactor) operation. Consequently, little attention has been given to non-electroactive bacteria in the same systems because of their incapability to acquire and transfer electrons directly. However, in this study, we identified some functionally important non-electroactive bacteria from biofilm established under low-voltage (0, 0.3, 0.5 and 1 V) electric fields in AnMBRs, designated as E-AnMBRs in this study. During the whole experiment, non-electroactive bacteria, mainly belonging to Proteobacteria, Bacteroidetes, and Chloroflexi, were found in all biofilm samples taken from each E-AnMBR. Under 0.3 V and 1 V conditions, non-electroactive bacteria did not seem to contribute to the development of biofilm significantly. Whereas under 0.5 V conditions, the growth of non-electroactive bacteria contributed up to 0.61 kPa/day biofilm formation. Therefore, 0.5 V was identified as a critical voltage, leading to the most severe biofilm formation. The microbial community structure in the reactor with a 0.5 V electric field was distinctly unique, caused by the increase of non-electroactive bacterial activity and the upregulation of their metabolic pathways. Notably, functional genes involved in carbon metabolism and oxidative phosphorylation pathway were upregulated. Furthermore, the 0.5 V electric field enhanced the protein/polysaccharide ratio and increased zeta potential to 31.6 mV (p < 0.01) of the biofilm samples. This was because upregulating quorum sensing genes accelerated the coordinated gene regulations and functional activities among non-electroactive bacteria.

Low voltage electric field mediating gravity-driven membrane bioreactor in treating saline wastewater: removal improvement and membrane fouling control

Gravity-driven membrane bioreactor (GDMBR) endowed with low maintenance and energy consumption owing to its combinations between biological degradation and membrane rejection, however, has not been reported in treating the saline wastewater due to the potential biological inhibition. This study investigated the effects of salt on GDMBR performance, and introduced a novel low voltage electric field (eGDMBR) with hopes to mediate the biological activity and improve the filtration performance. The influence of different low voltage electric fields (0.25 V, 0.50 V, and 0.75 V) on the flux variations and contaminants removal of eGDMBR were investigated. The results demonstrated that integrating low voltage electric field into GDMBR would not impact the appearance of flux stabilization, but delivered a significant influence on its stabilized flux level, and 0.50 V was the optimized voltage, contributing to a substantial flux improvement of 47.10 % in eGDMBR-0.50. Moreover, with the assistance of low voltage electric fields, eGDMBR process obtained an effective removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N) and total phosphorus (TP), accounting for average removal efficiency of 54.01 %, 73.08 % and 25.74 %, respectively. Compared to the control, coupling 0.50 V voltage electric field to GDMBR was beneficial to engineer a loose, porous and heterogeneous structure of membrane biofilm and also reduce the accumulation of extracellular polymeric substance (EPS), significantly contributing to alleviating the membrane fouling. Furthermore, with the assistance of low voltage electric fields, the Proteobacteria was enriched by a relative abundance of 58.58 % in the membrane biofilm of eGDMBR-0.50, which was in favor of the degradation of COD and NH4+-N. Therefore, these findings indicated that eGDMBR conferred significant superiorities in treating the saline wastewater and mitigating membrane fouling.

4’-pentyl-4-cyanobiphenyl - 5CB

ABSTRACT Thermotropic liquid crystals have been known from 1888, but have experienced little practical application or commercial usage up until the 1970s, when they were sandwiched between conducting glass plates and an electric field was applied. Their response to the field precipitously demonstrated an opportunity for creating and changing visible images using low voltage electric fields. At a similar time, the world was about to experience the invention of integrated electrical circuits, or CHIPs as they became known. The strange connection between solid-state semi-conductor electronics and the imagery provided via semi-fluid non-conducting organic materials meant that visual communication devices became a possibility, provided that there was an associated revolution in the design of nematogens as no suitable research or commercial materials were available at that time. With the synthesis of cyanobiphenyls by chemists at the University of Hull in 1972, within two years the picture dramatically changed. This is the story of the birth 5CB.

The antibacterial mechanism of compound preservatives combined with low voltage electric fields on the preservation of steamed mussels (Mytilus edulis) stored at ice-temperature.

Mussels are a kind of economically valuable ocean bivalve shellfish. It has a short harvest period and is susceptible to contamination during storage and processing. Having proper preservation methods is critical to prevent quality deterioration. However, the effect of low voltage variable frequency electric field and compound preservative on the freshness of steamed mussels in ice-temperature storage are still unknown. We utilized the method of coefficient variation weighting to calculate the overall scores of steamed mussels stored under different preservation conditions. The protein physicochemical properties of samples, the growth curves of two dominant spoilage bacteria; Bacillus subtilis and Pseudomonas in the mussels as well as the Structural changes of the cell membranes were mensurated. The results show that compared with the preservative group and the low voltage variable frequency electric field group, the compound preservatives combined with the electric field group had the highest overall score and thus the best preservation effect. Compared with the blank group, the total sulfhydryl content and myogenic fibrin content of the combined group decreased at the slowest rate, 19.46%, and 44.92%, respectively. The hydrophobicity of the protein surface increased by only 5.67%, with the best water retention, indicating that the samples of the combined group had the least protein deterioration in the combined group. The inhibition mechanism of the combined group inhibited the growth of two dominant spoilage bacteria: Bacillus subtilis and Pseudomonas, in the mussels, destroying the integrity of the cell membrane structure and changing the cell morphology. Overall, we found that the combination of the composite preservatives and the low voltage variable frequency electric field can maintain the best quality of steamed mussels during ice-temperature storage and slow down the rate of protein deterioration during storage. This study proposed a new method of mussel preservation, which provides a new idea for the application of low voltage variable frequency electric field and compound preservative in the preservation of aquatic products.

Mormyrid fish as models for investigating sensory-motor integration: A behavioural perspective.

Animals possess senses which gather information from their environment. They can tune into important aspects of this information and decide on the most appropriate response, requiring coordination of their sensory and motor systems. This interaction is bidirectional. Animals can actively shape their perception with self-driven motion, altering sensory flow to maximise the environmental information they are able to extract. Mormyrid fish are excellent candidates for studying sensory-motor interactions, because they possess a unique sensory system (the active electric sense) and exhibit notable behaviours that seem to be associated with electrosensing. This review will take a behavioural approach to unpicking this relationship, using active electrolocation as an example where body movements and sensing capabilities are highly related and can be assessed in tandem. Active electrolocation is the process where individuals will generate and detect low-voltage electric fields to locate and recognise nearby objects. We will focus on research in the mormyrid Gnathonemus petersii (G.petersii), given the extensive study of this species, particularly its object recognition abilities. By studying object detection and recognition, we can assess the potential benefits of self-driven movements to enhance selection of biologically relevant information. Finally, these findings are highly relevant to understanding the involvement of movement in shaping the sensory experience of animals that use other sensory modalities. Understanding the overlap between sensory and motor systems will give insight into how different species have become adapted to their environments.

Manipulation of coacervate droplets with an electric field

Many biopolymers are highly charged, and as in the case of many polymer mixtures, they tend to phase separate as a natural consequence of chain connectivity and an associated relatively low entropy of polymer mixing. Recently, it has become appreciated that the phase-separated structures formed by such polyelectrolyte blends, called "complex coacervates," underlie numerous biological structures and processes essential to living systems, and there has been intense interest in understanding the unique physical features of this type of phase-separation process. In the present work, we are particularly concerned with the field responsiveness of stabilized coacervate droplets formed after the phase separation of polyelectrolyte blend solution and then exposed to deionized water, making the droplet interfacial layer acquire a viscoelastic character that strongly stabilizes it against coalescence. We show that we can precisely control the positions of individual droplets and arrays of them with relatively low-voltage electric fields (on the order of 10 V/cm) and that the imposition of an oscillatory field gives rise to chain formation with coarsening of these chains into long fibers. Such a phase-separation-like process is generally observed in electrorheological fluids of solid colloidal particles subjected to much larger field strengths. The key to these coacervates' electrorheological properties is the altered interfacial viscoelastic properties when the droplets are introduced into deionized water and the associated high polarizability of the droplets, similar to the properties of many living cells. Since many different molecular payloads can be incorporated into these stable droplets, we anticipate many applications.

Facile Preparation of Mechanical Reinforced and Biocompatible Silk Gels

Nontoxic and controllable way to fabricate silk fibroin (SF) gel with high mechanical properties is of critical important to biomaterial in tissue engineering. Electrochemically triggered electrophoretic migration and electric charge of the silk molecules both contributed to SF microspheres and electronic gel (e-gel) formation by sol-gel transition. In this study, a novel silk pH e-gel with higher mechanical property was prepared by combining low-voltage electric fields with isoelectric point (pI) adjustment. This green process was mild and friendly without chemical crosslinker. Compressive modulus of the silk pH e-gel was up to 70 MPa that was significantly higher than that of SF gelation spontaneously. Furthermore, analysis of molecule conformation of the silk pH-e-gel demonstrated that most of random coil structures transformed into α-helix and a little β-sheet structures during this process. The silk pH e-gel was loaded with rhodamine B and showed an obvious sustainable release profile. Accumulation releasing amounts was approximately 60% at day 9. Cytocompatibility of the silk pH-e-gel was evaluated by epithelial cell. The results showed that the gels could support the cell growth and proliferation in vitro. Finally, gel biodegradation was assessed by protease XIV. After biodegradation for 28 days, remaining weight of the gel was about 20.23±2.59 wt%, indicating its good biodegradability. This novel process was established successfully by combining low voltage field with pH-control, which provided an alternative material for regenerative medicine.

Sensory Hair Cells: An Introduction to Structure and Physiology.

Sensory hair cells are specialized secondary sensory cells that mediate our senses of hearing, balance, linear acceleration, and angular acceleration (head rotation). In addition, hair cells in fish and amphibians mediate sensitivity to water movement through the lateral line system, and closely related electroreceptive cells mediate sensitivity to low-voltage electric fields in the aquatic environment of many fish species and several species of amphibian. Sensory hair cells share many structural and functional features across all vertebrate groups, while at the same time they are specialized for employment in a wide variety of sensory tasks. The complexity of hair cell structure is large, and the diversity of hair cell applications in sensory systems exceeds that seen for most, if not all, sensory cell types. The intent of this review is to summarize the more significant structural features and some of the more interesting and important physiological mechanisms that have been elucidated thus far. Outside vertebrates, hair cells are only known to exist in the coronal organ of tunicates. Electrical resonance, electromotility, and their exquisite mechanical sensitivity all contribute to the attractiveness of hair cells as a research subject.

Assessing the potential for using low-frequency electric deterrent barriers to reduce lake sturgeon (Acipenser fulvescens) entrainment

Given the limited evidence on utilizing low-frequency electrical fields as deterrents to fish, we studied lake sturgeon (Acipenser fulvescens Rafinesque, 1817) behavioural responses and short-term physiological reactions to low-frequency (0.1–50 Hz) low-voltage (0.024–0.3 v) electric fields. Fish from 2 year classes were used as a means of including size considerations in the study. Individuals from both year classes exhibited differing responses to the same electric fields, with smaller, younger fish being more reactive to the electric stimulation of the fields than /older, larger fish. The smaller, younger fish also had reduced weight gain 30 days post experiment compared with fish that were a year older. Short-term physiological effects were observed in the older, larger fish in the form of elevated blood glucose levels. Our results show that individuals can acclimatize to electric fields in a relatively short time period and that larger individuals tend to be less affected by low-frequency/low-voltage electric fields than smaller fish. Testing the utility of electric deterrents in a more realistic riverine setting using pulsating electric field is, therefore, highly recommended to ensure decisions regarding the implementation of low-frequency/low-voltage electric barrier systems to reduce entrainment adequately account for possible sublethal effects on lake sturgeon.

A multi-technique phytoremediation approach to purify metals contaminated soil from e-waste recycling site

Multiple techniques for soil decontamination were combined to enhance the phytoremediation efficiency of Eucalyptus globulese and alleviate the corresponding environmental risks. The approach constituted of chelating agent using, electrokinetic remediation, plant hormone foliar application and phytoremediation was designed to remediate multi-metal contaminated soils from a notorious e-waste recycling town. The decontamination ability of E. globulese increased from 1.35, 58.47 and 119.18 mg per plant for Cd, Pb and Cu in planting controls to 7.57, 198.68 and 174.34 mg per plant in individual EDTA treatments, respectively, but simultaneously, 0.9–11.5 times more metals leached from chelator treatments relative to controls. Low (2 V) and moderate (4 V) voltage electric fields provoked the growth of the species while high voltage (10 V) had an opposite effect and metal concentrations of the plants elevated with the increment of voltage. Volumes of the leachate decreased from 1224 to 134 mL with voltage increasing from 0 to 10 V due to electroosmosis and electrolysis. Comparing with individual phytoremediation, foliar cytokinin treatments produced 56% more biomass and intercepted 2.5 times more leachate attributed to the enhanced transpiration rate. The synergistic combination of the individuals resulted in the most biomass production and metal accumulation of the species under the stress condition relative to other methods. Time required for the multi-technique approach to decontaminate Cd, Pb and Cu from soil was 2.1–10.4 times less than individual chelator addition, electric field application or plant hormone utilization. It's especially important that nearly no leachate (60 mL in total) was collected from the multi-technique system. This approach is a suitable method to remediate metal polluted site considering its decontamination efficiency and associated environmental negligible risk.

Addition of iron oxides in sediments enhances 2,3,4,5-tetrachlorobiphenyl (PCB 61) dechlorination by low-voltage electric fields

The presence of iron oxides in sediments significantly improves anaerobic dechlorination of PCB (i.e., PCB 61) in bioelectrochemical reactors.

Electric Field-Induced Disruption and Releasing Viable Content from Extracellular Vesicles.

In order to more fully elucidate the biogenesis of exosomes, a type of extracellular vesicles (EVs) and understand the role of EVs in disease processes, it is necessary to develop methods to capture EVs and induce the unloading of viable cargo. Traditionally, ultracentrifugation followed by chemical based EV lysis techniques is used to isolate these extracellular vesicles and release their internal content. Here, we describe a novel technique for capturing and releasing exosomal content through magnetic bead-based EV extraction coupled with electric field induced release and measurement (EFIRM). The usage of low-voltage electric fields allows the EV to be lysed without chemical treatment, and surface immobilized probes can allow for the rapid capture of the content of lysed EVs. EFIRM as an integrated EV lysing and analysis system offers great potential for the investigation of EVs in clinical and basic science contexts.

Reversible Assembly of Colloidal Particles Using Low Frequency Pulsed DC Electric Fields

We present the reversible assembly of colloidal nanoparticles in organic solvents using low voltage and low frequency pulsed DC electric fields. Commercially available and custom nanoparticles (diameter ~ 50-200 nm) were suspended in organic solvents at concentrations of 0.25-50 wt% and sandwiched between indium tin oxide (ITO) electrodes of spacing 25 μm-2mm. Using square waves of frequency 0.25-5 Hz, voltages 0.5-5V, and DC offset 0.25-2.5V, colloidal suspensions were actuated for switchable contrast. Upon switching off the electric field, the assembled nanoparticles are able to resuspend within seconds. Using patterned electrodes, lateral electromigration of the particles was demonstrated. Depletion of the particles to the electrode regions resulted in transparency in the non-patterned regions. The distinct contrast generated can be exploited for tunable display applications. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-679931.

Metal nanoparticle dispersion, alignment, and assembly in nematic liquid crystals for applications in switchable plasmonic color filters and E-polarizers.

Viewing angle characteristics of displays and performance of electro-optic devices are often compromised by the quality of dichroic thin-film polarizers, while dichroic optical filters usually lack tunability and cannot work beyond the visible part of optical spectrum. We demonstrate that molecular-colloidal organic-inorganic composites formed by liquid crystals and relatively dilute dispersions of orientationally ordered anisotropic gold nanoparticles, such as rods and platelets, can be used in engineering of switchable plasmonic polarizers and color filters. The use of metal nanoparticles instead of dichroic dyes allows for obtaining desired polarizing or scattering and absorption properties not only within the visible but also in the infrared parts of an optical spectrum. We explore spontaneous surface-anchoring-mediated alignment of surface-functionalized anisotropic gold nanoparticles and its control by low-voltage electric fields, elastic colloidal interactions and self-assembly, as well as the uses of these effects in defining tunable properties of the ensuing organic-inorganic nanostructured composites. Electrically tunable interaction of the composites may allow for engineering of practical electro-optic devices, such as a new breed of color filters and plasmonic polarizers.

Self-assembly and electrostriction of arrays and chains of hopfion particles in chiral liquid crystals.

Some of the most exotic condensed matter phases, such as twist grain boundary and blue phases in liquid crystals and Abrikosov phases in superconductors, contain arrays of topological defects in their ground state. Comprised of a triangular lattice of double-twist tubes of magnetization, the so-called ‘A-phase’ in chiral magnets is an example of a thermodynamically stable phase with topologically nontrivial solitonic field configurations referred to as two-dimensional skyrmions, or baby-skyrmions. Here we report that three-dimensional skyrmions in the form of double-twist tori called ‘hopfions’, or ‘torons’ when accompanied by additional self-compensating defects, self-assemble into periodic arrays and linear chains that exhibit electrostriction. In confined chiral nematic liquid crystals, this self-assembly is similar to that of liquid crystal colloids and originates from long-range elastic interactions between particle-like skyrmionic torus knots of molecular alignment field, which can be tuned from isotropic repulsive to weakly or highly anisotropic attractive by low-voltage electric fields.

Standards of care and novel approaches in the management of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor in adults. Standard therapeutic approaches provide modest improvement in the progression-free and overall survival, necessitating the investigation of novel therapies. We review the standard treatment options for GBM and evaluate the results obtained in clinical trials for promising novel approaches, including the inhibition of angiogenesis, targeted approaches against molecular pathways, immunotherapies, and local treatment with low voltage electric fields.

Electrically controlled topological defects in liquid crystals as tunable spin-orbit encoders for photons

We demonstrate experimentally that topological defects of vertically aligned nematic liquid crystal films induced by electric fields can be used as highly efficient natural optical spin-orbit encoders that do not need machining techniques. Moreover, we show that both the operating wavelength and operation mode of such natural quantum optical interfaces can be tuned in real time using low-voltage electric fields.

Using mesoporous carbon electrodes for brackish water desalination

Electrosorptive deionisation is an alternative process to remove salt ions from the brackish water. The porous carbon materials are used as electrodes. When charged in low voltage electric fields, they possess a highly charged surface that induces adsorption of salt ions on the surface. This process is reversible, so the adsorbed salt ions can be desorbed and the electrode can be reused. In the study, an ordered mesoporous carbon (OMC) electrode was developed for electrosorptive desalination. The effects of pore arrangement pattern (ordered and random) and pore size distribution (mesopores and micropores) on the desalination performance was investigated by comparing OMC and activated carbon (AC). It were revealed from X-ray diffraction and N 2 sorption measurements that AC has both micropores and mesopores, whereas ordered mesopores are dominant in OMC. Their performance as potential electrodes to remove salt was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests at a range of electrolyte concentrations and sweep rates. It is deduced that under the same electrochemical condition the specific capacitance values of OMC electrode (i.e. 133 F/g obtained from CV at a sweep rate of 1 mV/s in 0.1 M NaCl solution) are larger than those of AC electrode (107 F/g), suggesting that the former has a higher desalting capacity than the latter. Furthermore, the OMC electrode shows a better rate capacity than the AC electrode. In addition, the desalination capacities were quantified by the batch-mode experiment at low voltage of 1.2 V in 25 ppm NaCl solution (50 μs/cm conductivity). It was found that the adsorbed ion amounts of OMC and AC electrodes were 11.6 and 4.3 μmol/g, respectively. The excellent electrosorptive desalination performance of OMC electrode might be not only due to the suitable pore size (average of 3.3 nm) for the propagation of the salt ions, but also due to the ordered mesoporous structure that facilitates desorption of the salt. Based on the results, it was found that the development of an ordered mesoporous structure and the control of the number of micropores are two important strategies for optimising electrode material properties for electrosorptive deionisation.

The use of transient electric birefringence to characterize the conformation of DNA in solution, the mechanism of DNA gel electrophoresis, and the structure of agarose gels

Abstract Two small, 153 base-pair (bp) DNA restriction fragments, one of which migrates anomalously slowly during electrophoresis in polyacrylamide gels, have been characterized by transient electric birefringence (TEB). The decay of the birefringence of the anomalously slowly migrating fragment is faster than that of the normal fragment under a variety of buffer conditions, suggesting that the anomalous fragment is stably bent or curved in free solution. Reversing field experiments suggest that both the anomalous and normal DNA fragments orient in the electric field by a slow induced dipole mechanism. Birefringence relaxation times have also been measured for three DNA molecules embedded in agarose gels of various concentrations. The embedded DNA molecules become oriented in the electric field, just as in free solution. If the median pore diameter of the gel is approximately twice as large as the apparent end-to-end length of the DNA in solution, the relaxation times of the embedded DNA molecules are unaffected by the presence of the gel, indicating that the DNA retains its usual wormlike coil conformation in the gel matrix. However, as the end-to-end length of the DNA approaches the median pore diameter of the gel, the DNA molecules become stretched out and elongated in the electric field, leading to a repetitive, or end-on, mode of migration during electrophoresis. The relaxation times of the stretched DNA molecules scale as the 2.8 power of molecular weight, in reasonable agreement with reptation theories. The structure of agarose gels has also been characterized by TEB. The long, low voltage electric fields used for pulsed field gel electrophoresis (PFGE) cause extensive orientation of the agarose gel fibers. A wide range of relaxation times is observed after the field is removed, corresponding to the orientation of gel fibers up to 22 μm in length. The sign of the birefringence is variable, indicating that the gel fibers can be oriented in different directions in different parts of the gel. Surprisingly, the sign of the birefringence reverses upon field reversal, suggesting that the gel fibers change their direction of orientation in reversing electric fields. This anomalous orientation behavior is not observed for chemically crosslinked polyacrylamide gels. The apparent orientation and reorientation of agarose gel fibers in rapidly reversing electric fields may lead to ‘dynamic pores’ in the gel matrix, facilitating the migration of very large DNA molecules during PFGE.

Transient electric birefringence of agarose gels. I. Unidirectional electric fields.

The orientation of agarose gels in pulsed electric fields has been studied by the technique of transient electric birefringence. The unidirectional electric fields ranged from 2 to 20 V/cm in amplitude and 1 to 100 s in duration, values within the range typically used for pulsed field gel electrophoresis (PFGE). Agarose gels varying in concentration from 0.3 to 2.0% agarose were studied. The sign of the birefringence varied randomly from one gel to another, as described previously [J. Stellwagen & N.C. Stellwagen (1989), Nucleic Acids Research, Vol. 17, 1537-1548]. The sign and amplitude of the birefringence also varied randomly at different locations within each gel, indicating that agarose gels contain multiple subdomains that orient independently in the electric field. Three or four relaxation times of alternating sign were observed during the decay of the birefringence. The various relaxation times, which range from 1 to approximately 120 s, can be attributed to hierarchies of aggregates that orient in different directions in the applied electric field. The orienting domains range up to approximately 22 microns in size, depending on the pulsing conditions. The absolute amplitude of the birefringence of the agarose gels increased approximately as the square of the electric field strength. The measured Kerr constants are approximately 5 orders of magnitude larger than those observed when short, high-voltage pulses are applied to agarose gels. The increase in the Kerr constants in the low-voltage regime parallels the increase in the relaxation times in low-voltage electric fields. Birefringence saturation curves in both the low- and high-voltage regimes can be fitted by theoretical curves for permanent dipole orientation. The apparent permanent dipole moment increases approximately as the 1.6 power of fiber length, consistent with the presence of overlapping agarose helices in the large fiber bundles orienting in low-voltage electric fields. The optical factor is approximately independent of fiber length. Therefore, the marked increase in the Kerr constants observed in the low-voltage regime is due to the large increase in the electrical orientation factor, which is due in turn to the increased length of the fiber bundles and domains orienting in low-voltage electric fields. Since the size of the fiber bundles and domains approximates the size of the DNA molecules being separated by PFGE, the orientation of the agarose matrix in the applied electric field may facilitate the migration of large DNA molecules during PFGE.