Transport by Electric Field

Returning to a horizontal support, drops collide with the lateral walls surrounding the plate. They are then reflected and resume their motion, following complex trajectories. For better control of the experiment, it is sometimes advantageous to confine a drop between two rails (non-wettable ribbons). 

In the absence of rails, a drop may attempt to traverse a prior trajectory. Such a region turns out to be hostile (less wettable), and the drop cannot always get across. The discussion of crossing events is complicated because inertia must be taken into account. 

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Related to this last process enhancement is the use of an EK barrier, or fence. The EK barrier has two different objectives depending on its use (a) to precipitate or transform heavy metals transported by electric fields or (b) to stop a hydraulic generated flow of liquid with contaminants by the application of an electric field in the opposite direction. In the first approach, zero-valent iron has mainly been used... 

The switching or memory phenomena induced by electric field application or photo irradiation have been studied on Mott insulators, charge ordered insulators, and N-I transition systems and were found to be fast phase transitions in general. For the former two systems, the phase transitions caused a pronounced change in reflectance and conductivity from insulating to metallic features. The third system also exhibited a change in conductivity and dielectric response connected with the transports of solitons and/or domain walls, dynamic dimerization, and... 

Electric fields use in soil restoration has been focused on contaminant extraction by their transport under electroosmosis and ionic migration. Contaminant extraction by electric fields is a successful technique for removal of ionic or mobile contaminants in the subsurface. However, this technique might not be effective in treatment of soils contaminated with immobile and/or trapped organics, such as dense non aqueous phase liquids (DNAPLs). For such organics, it is possible to use electric fields to stimulate in situ biodegradation under either aerobic or anaerobic conditions. It is necessary to evaluate the impact of dc electric fields on the biogeochemical interactions prior to application of the technique. It is not clear yet how dc electric fields will impact microbial adhesion and transport in the subsurface. Further, the effect of dc fields on the activity of microorganisms in a soil matrix is not yet well understood. 

Transport of the vapourized material through the reduced atmosphere from the source to a substrate. During their flight, collisions with residual gas molecules can occur depending on vacuum conditions and source to substrate distance. The volatilized coating material species can be activated or ionized by various means and the ions can be accelerated by electric fields. 

Alshawabkeh AN, Ozsu-Acar E, Gale RJ, Puppala SK. (1998). Remediation of soils contaminated with tetraethyl lead by electric fields. Transportation Research Record 1615 79-85. 

Pribyl M, Chmelikova R, Hasal P, Marek M. (2001). Modeling of hydrogel immobihzed enzyme reactors with mass-transport enhancement by electric field. Chemical Engineering Science 56 433-442. 

We have given perhaps undue attention to the mobile carrier mechanism because at one time it was assumed that the Na and K transport in excitable cell membranes occurred precisely via this mechanism. In 1965, Chandler and Meves undertook an experiment to assess the aforementioned specifics of the high-frequency conductance. A nerve fiber was placed in a solution containing no Na or K ions. This precluded direct current through the membrane. However, if there had been any mobile charged carriers in the membrane, the authors would have detected current on application of a variable field. The authors did not observe a detectable current under these conditions, from which it could be deduced that the transport systems of excitable membrane are structured as ion channels whose conductance is controlled by electric field. 

Description The special hydrod3mamics of droplet transport cause a pairwise alignment of the droplets. For this particular configuration, the smaller droplet is automatically placed in proximity to the larger droplet and is kept at this position by the wall friction-driven recirculating flow of the continuous phase. Hence, droplets are transported as droplet pairs and can be directly merged at a target position by electrical field actuation. 

Biomolecules can be manipulated efficiently by electric fields in various ways. This article gives a brief survey of the following methodologies DC electrokinetic transport (electrophoresis and electroosmosis), AC dielectrophoretic transport, and the electrically induced modulation of the biomolecule conformation. Selected examples for applications will be described as based on these mechanisms, including molecule transport and separation, the dielectrophoretic trapping of molecules, and two schemes in biosensing involving smart (switchable) bio-surfaces and nanopore-patterned membranes. 

The driving force for ion transport in a polymer phase can be either a concentration gradient (diffusive transport), an electric field (migration), or both. The resulting flux of the ionic species i, Ji, is usually described by the Nernst-Planck equation ... 

Superparamagnetism, which is very useful in drug delivery because the superparamagnetic iron oxide nanoparticles are transported to the desired site by electrical field effects remain at target site even after removal of the magnetic field (Kalia et al. 2014). 

Other aspect to which the majority of researchers do not pay attention, especially in the studies on chemical weathering of insulating materials destined to electrical cables and wires is the evaluation of altered functional characteristics by electrical field. This aspect is quite important for the security of aerial and buried electric transport networks. The channels appeared as the result of the orientation of dipoles in oxidizing polymers die to electrical field allow the further penetration of water which forms electrical trees [39,40]. The length, the density and the size extension of these defects influence deeply the durability of electrical insulator. Moreover, the continuous action of electrical field amplifies the degradation, which increases proportionally the failure of outdoor operating cabled. 

Fig. 7 Schematic of proton transport in and through Nafion membranes. Protons are generated by hydrogen oxidation on a catalyst surface. The protons move laterally in the catalyst layer (uniform potential field) until they find an opening into the hydrophilic domains of the Nafion. The protons are transported across the membrane by electric field-assisted motion. At low applied potentials, the transport across the membrane is limiting, but at high applied potentials, the proton motion is limited by diffusion in the catalyst layer to the openings of the hydrophilic domains...

Figure 11-1. A simplified model of intermolecular charge transport in electric field. Each box represents a molecule. The size of the boxes is determined by the conjugation of the molecule, and the distances between boxes are the distances between molecules in macroscopic crystalline structure. The bias electric field (E) provides a directed transportation of excitons or charge carriers generated after dissociation of exdton...

The bipolar junction transistor (BIT) consists of tliree layers doped n-p-n or p-n-p tliat constitute tire emitter, base and collector, respectively. This stmcture can be considered as two back-to-back p-n junctions. Under nonnal operation, tire emitter-base junction is forward biased to inject minority carriers into tire base region. For example, tire n type emitter injects electrons into a p type base. The electrons in tire base, now minority carriers, diffuse tlirough tire base layer. The base-collector junction is reverse biased and its electric field sweeps tire carriers diffusing tlirough tlie base into tlie collector. The BIT operates by transport of minority carriers, but botli electrons and holes contribute to tlie overall current. 

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