Electrohydrodynamic Methods Research Articles

Electrohydrodynamic methods applied for the co-encapsulation of polyphenols and vitamins in pullulan microstructures

Recently, electrospun micro/nanostructures attracted a lot of attention and have shown to have a significant potential for drug delivery. This work focuses on the application of pullulan to prepare different micro/nanostructures. When pullulan is used on the submicron-to-nanoscale dimension, it demonstrates to have some advantages for biomedical, pharmaceutical, and engineering applications. Two different biomolecules were used as models for polyphenols and vitamins encapsulation, Epigallocatechin-3-gallate (EGCG) and vitamin B12, respectively. So, the current work aims to develop pullulan microstructures containing EGCG, Vitamin B12 and the combination of both (EGCG+VitB12) using Electrohydrodynamic techniques (EHD). The encapsulation was performed for different concentrations of pullulan (10–20% w/v) containing 1% w/w of active compound, resulting in the production of micro/nanoparticles, fibers, or mixture of them. Through the evaluation of the release profiles, it was concluded that the longest releases are associated with the structures loaded with EGCG+VitB12 and with highest pullulan concentration (20% w/v). The experimental release profiles were evaluated using different kinetic models, and the results indicated that the Weibull model was the most appropriate. High encapsulation efficiencies were obtained for all samples (>82.4%). It was also concluded that co-encapsulated compounds had very similar release profiles and the main release mechanism was associated with the Fickian diffusion transport.

A novel and facile synthesis of Ag-doped TiO2 nanofiber for airborne virus/bacteria inactivation and VOC elimination under visible light

There are strong demands for high biocidal and degassing performance of fibrous air filters, and the development of photocatalytic nanofiber operating under visible-light remains a challenge. We present a novel technique for the fabrication of TiO2 nanofibers (NFs) with Ag components concentrated on the fiber surface by inducing electrohydrodynamic transportation of Ag+ during electrospinning with negative electric potential. Unique localized Ag components on the surface of TiO2 were beneficial for providing visible-light-response ability, and for offering small crystallite size, low-bandgap energy and recombination rate for fast and efficient photocatalytic reaction in air media. As consequences, optimized Ag/TiO2 NFs exhibited remarkable ability for airborne bacteria and virus inactivation, as well as notable photocatalytic activity toward acetaldehydes under visible light. Moreover, this study presents a systematic comparison of Ag/TiO2 NFs and Ag/TiO2 NPs prepared by different electric potential and electrohydrodynamic methods.

Influence of Electrohydrodynamic Flows on Intensification of the Heat- and Mass Transfer Processes. Part III. Electroconvection and Electrohydrodynamic Pumps in Cooling and Thermostating Systems

The efficiency of the electrohydrodynamic (EHD) cooling and thermostating systems of electronic and electrical devices is investigated. A design of electroconvective cooling of an X-ray generator is proposed, the effectiveness of which is confirmed on laboratory models and full-scale samples. The anode temperature was reduced by a factor of two, the duration of the emitter operation increased, the reliability of the device improved. Various methods of cooling a high-voltage transformer are presented allowing to increase the specific power, reduce the weigh, size parameters, and temperature of the coolant, augment the resource. Studies have been conducted to establish the possibility of thermostating the heat-emitting element (block) by EHD methods when both external and internal conditions change. The design of an EHD thermostat with an automatic thermal stabilization system has been developed and tested (the temperature is maintained with an accuracy of ± 0.05 °С). A frame with an EHD liquid circuit and an EHD thermostat has been designed, which allows to significantly reduce longitudinal temperature differences and its deformation. The high efficiency of EHD cooling methods is shown by an example of a block of light-emitting diodes, small elements and components of electronic equipment, the use of electrodes – wires with a perforated insulating coating when cooling flat heat-emitting surfaces; a sevenfold increase in the heat transfer coefficient is achieved.

Particulate Matter Emission Reduction from Marine Diesel Engines by Electrohydrodynamic Methods

Abstract Particulate matter (PM) and gaseous compounds (SO2, NOx, VOC) emitted by diesel engines causes serious global environmental problems and health impact. Despite numerous evidences about the harmfulness of diesel particles, the PM emission by diesel engines used by ships, cars, agricultural machines, or power generators is still unregulated, and the efficient removal of PM from diesel exhausts is still the major technological challenge. In order to comply with the International Maritime Organization regulation, the NOx emission is reduced by using selected catalytic reactor, and sulphur oxide emission has been reduced by using fuels of low sulphur content. However, both of those measures cannot be used for the reduction of PM emission produced during combustion of marine fuels. The lack of appropriate regulations results from insufficiently developed technology, which could remove those particles from exhaust gases. Conventional scrubbers currently available on the market remove only sulphur oxide with required collection efficiency, but the collection efficiency for PM2.5 is below 50%. The article discusses the technical means used for the removal of PM from marine diesel engines via applying electrohydrodynamic methods, in particular electrostatic agglomeration, as a method of nanoparticles coagulation to larger agglomerates, which could operate in two-stage electrostatic precipitation systems, and electrostatic scrubbers, which remove particles by electrically charged water droplets. The experimental results were obtained for a 2-stroke 73 kW diesel engine fuelled with marine gas oil (MGO). The agglomerator allowed increasing the collection efficiency from diesel exhausts for PM2.5 particles by about 12%, compared to electrostatic precipitator operating without agglomerator, and the total mass collection efficiency was above 74%. The collection efficiency of electrostatic scrubber was higher than 95wt.%. The advantage of using the electrostatic scrubber is that it can also reduce the SO2 emission by more than 90%, when HFO is used.

Electrohydrodynamic (EHD) Bioprinting of Polycaprolactone Scaffolds

This study is combined a 3D printing and Electrohydrodynamic (EHD) methods to fabricate a 3D PCL scaffolds for tissue engineering. Various kV values were applied to the different PCL solutions to investigate the effect of the voltage on scaffolds. The morphology of 3D-EHD printed PCL scaffolds were characterized by an Optical Microscope. 10 wt.% PCL up to 3 kV was obtained best sample to use for tissue engineering scaffolds.

Electrohydrodynamic methods for the development of pulmonary drug delivery systems

Electrospinning and electrospraying are two highly versatile and scalable electrohydrodynamic methods, which have attracted considerable attention during the last years towards the fabrication of polymer-based drug delivery systems. The latter may be obtained in the form of nano- or microfibers (via electrospinning) or as drug-loaded nano- and microparticles (via electrospraying). This review article begins with an introduction on the basic principles and the important influencing parameters governing the electrospinning/electrospraying processes, followed by an overview on their use for the development of nano/microfibers and nano/microparticles destined for use in pharmaceutical applications. Focus is given on research efforts targeting in the formulation of drug delivery systems and devices designed for pulmonary drug delivery applications thus emphasizing on the potential use of electrospinning and electrospraying in the area of inhaled medicines.

Polymeric Based Therapeutic Delivery Systems Prepared Using Electrohydrodynamic Processes.

The development of therapeutic dosage (e.g. pharmaceutical) systems is an ongoing process which, in recent times has incorporated several emerging disciplines and themes at timely intervals. While the concepts surrounding dosage forms have developed and evolved, many polymeric excipients remain as the preferred choice of materials over existing counterparts, serving functions as matrix materials, coatings and providing other specific functional properties (e.g. adhesion, controlled release and mechanical properties). There have been, however, developments in the deployment of synthetic polymeric materials (e.g. polycaprolactone, poly lactic co-glycolic acid) when compared to naturally occurring materials (e.g. lactose, gelatin). Advances in pharmaceutical process technologies have also provided novel engineering platforms to develop a host of exciting structure based materials ranging from the nanometer to the macro scales. Some of these structure enabling technologies include spray drying, super critical processing, microfluidics and even wet chemical methods. More recently electrohydrodynamic (EHDA) engineering methods have emerged as robust technologies offering potential to fabricate a plethora of generic structures (e.g. particles, fibres, bubbles and pre-determined patterns) on a broad scale range. This review focuses on key developments using various EHDA technologies for the pharmaceutical and biomaterial remits when selecting synthetic and/or naturally occurring polymers as pharmaceutical (and therapeutic) excipients. In addition, the underlying EHDA process principles are discussed along with key parameters and variables (both materials and engineering). EHDA technologies are operational at ambient conditions and recent developments have also demonstrated their viability for large scale production. These are promising technologies which have potential in established (e.g. films, dressings and microparticles) and emerging scientific themes (e.g. nanomedicines and tissue engineering).

Experimental and numerical insights into isotropic spreading and deterministic dewetting of dielectrowetted films.

Dielectrowetting effects of surface wrinkling, isotropic vs anisotropic spreading, electrode geometry, and deterministic dewetting are presented both experimentally and by 3D numerical modeling. The numerical results are generated by COMSOL in conjunction with the phase-field and electrohydrodynamic methods, including comparisons to experimental data. The dynamic behavior of the two-phase system has been accurately characterized on both the macro- and microscopic level. This work provides a deeper theoretical insight into the operating physics of dielectrowetting superspreading devices.

Quality assessment of electrohydrodynamic and microwave dehydrated banana slices

In contrast to the inherently energy-efficient electrohydrodynamic (EHD) methods, conventional drying methods are energy intensive. In the present study, comparisons were made between banana slice samples dried by high-voltage-DC powered multiple-point-to-plate electrodes and those dried by microwave (MW). For this purpose, banana slices were dried by an EHD drying system at electric field strengths of 6, 8, and 10 kV/cm and by an MW drying system at specific power levels of 9 and 18 W/g. No constant rate period was observed in the EHD; hence, the entire drying process occurred in the falling rate period, whereas the drying rates of MW-dried samples occurred at a constant rate and during the falling rate periods. Analysis of variance showed that drying method had a significant effect on drying time, rehydration ability, shrinkage, color parameters (L∗, a∗, b∗, and ΔE), and consumed energy. The mean values of specific consumed energy for EHD and MW drying methods were 0.34 and 9.66 kJ/g, respectively. In terms of drying time, EHD was not fast; however, its advantages of less energy requirement and great product quality including lower shrinkage, great rehydration ability, and better appearance make it a good choice for drying banana slices.

Pumpless dispensing of a droplet by breaking up a liquid bridge formed by electric induction

Dispensing uniform pico-to-nanoliter droplets has become one of essential components in various application fields from high-throughput bio-analysis to printing. In this study, a new method is suggested and demonstrated for dispensing a droplet on the top plate with an inverted geometry by using electric field. The process of dispensing droplets consists of two stages: (i) formation of liquid bridge by moving up the charged fluid mass using the electrostatic force between the charges on the fluid mass and the induced charges on the substrate and (ii) its break-up by the motion of the top plate. Different from conventional electrohydrodynamic methods, electric induction enables the droplets to be dispensed on various surfaces including non-conducting substrate. The use of capillarity with an inverted geometry removes the need of external pumps or elaborates control for constant flow feed. The droplet diameter has been characterized as a function of the nozzle-to-plate distance and the plate moving velocity. The robustness of the present method is shown in terms of nozzle length and applied voltage. Finally, its practical applicability is confirmed by rendering a 19 by 24 array of highly uniform droplets with only 1.8% size variation without use of any active feedback control.

Factors affecting the yield of polypyrrole colloids produced under electrohydrodynamic conditions

Several factors influencing the amount of polypyrrole colloid produced by electrohydrodynamic methods were investigated with the aim of increasing the yield of the process. The parameters investigated included solvent, pH, temperature, sonication, catholyte composition, cell design, flow rate, anode size and condition, monomer concentration and supporting electrolyte concentration. Particularly important in increasing the yield were the use of sonication, temperatures above room levels, adjustment of pH by alkaline catholyte, more efficient cell design, suitable flow rate and low monomer concentration. On the other hand, the amount of polymer deposited on the anode was not significantly reduced by any of the factors evaluated.