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Numerical simulations of thermoelectrohydrodynamic convection in a dielectric liquid inside a finite-length cylindrical annulus with a fixed temperature difference have been performed with increasing high-frequency electric tension under microgravity conditions. The electric field, coupled with the permittivity gradient, generates a dielectrophoretic buoyancy force whose non-conservative part can induce thermoelectric convection in the liquid. The liquid remains in a conductive state below a critical value of the applied electric voltage. At a critical value, a supercritical bifurcation occurs from the conductive state to a convective state made of stationary helicoidal vortices. A further increase of electric voltage leads to oscillatory helicoidal vortices and then to wavy patterns before spoke patterns dominate the convective flow. The dielectrophoretic force is shown to enhance the heat transfer from the hot to cold walls due to induced convective flows. Particularly, these results demonstrate that the dielectrophoretic buoyancy force holds promise to replace the gravitational force to induce efficient heat transfer in microgravity conditions, and they contribute to a better fundamental understanding of heat transfer in microgravity. [ABSTRACT FROM AUTHOR]

In this paper, a novel flexible piezoelectric thick-film generator is proposed to address the challenges caused by flexible deformation and high piezoelectricity. This improves the output charge of the generator, which breaks the limitation imposed by the rigid and brittle nature of traditional piezoelectric bulks on elastic strain and piezoelectric performance. Additionally, the low piezoelectric coefficient of piezoelectric polymer-based piezoelectric generators is also resolved. Given the high thickness precision of electrohydrodynamic jet printing technology, the facile production of 10-μm thick film components is achieved through a process of printing and layer-by-layer accumulation on a flexible substrate, which ensures the flexible deformation and piezoelectric characteristics of the functional film. To ensure that AC is converted into stable DC output, a bipolar charge collection circuit is developed. The printed thick film produces an excellent performance in surface uniformity and smoothness. Notably, the piezoelectric constant d 33 is measured to be approximately 80 pC/N, which is five times higher than the d 33 value of flexible PVDF films. Additionally, the strength of adhesion between the printed thick film and the flexible substrate is remarkably high, reaching up to 20 N, which is an order of magnitude higher than the magnetron sputtering method. In a single cycle, the forward charge output reaches an impressively high level of 260 nC, which is approximately thirteen times the charge transfer capability of PVDF flexible generator. Furthermore, a bipolar charge collection circuit is applied to convert AC into DC effectively. This increases the output voltage from 2 V to 4 V. The illumination of commercial electronic screens and 39 LED lights demonstrates the applicability of micron-scale jet-printed thick films in micro-energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper, we consider two-dimensional periodic capillary-gravity waves traveling under the influence of a vertical electric field. The full system is a nonlinear, two-layered, free boundary problem. The interface dynamics are derived by coupling Euler equations for the velocity field of the fluid with voltage potential equations governing the electric field. We first introduce the naive flattening technique to transform the free boundary problem into a fixed boundary problem. We then prove the existence of small-amplitude electrohydrodynamic waves with constant vorticity using local bifurcation theory. Moreover, we show that these electrohydrodynamic waves are formally stable in the linearized sense. Furthermore, we obtain a secondary bifurcation curve that emerges from the primary branch, consisting of ripple solutions on the interface. As far as we know, such solutions in electrohydrodynamics are established for the first time. It is worth noting that the electric field E 0 plays a key role in controlling the shapes and types of waves on the interface. [ABSTRACT FROM AUTHOR]

A thin liquid film spread over the inner surface of a rapidly rotating vial creates an aerodynamic cushion on which one or multiple droplets of various liquids can levitate stably for days or even weeks. These levitating droplets can serve as wall‐less (“airware”) chemical reactors that can be merged without touching—by remote impulses—to initiate reactions or sequences of reactions at scales down to hundreds of nanomoles. Moreover, under external electric fields, the droplets can act as the world's smallest chemical printers, shedding regular trains of pL or even fL microdrops. In one modality, the levitating droplets operate as completely wireless aliquoting/titrating systems delivering pg quantities of reagents into the liquid in the rotating vial; in another modality, they print microdroplet arrays onto target surfaces. The “airware”, levitated reactors are inexpensive to set up, remarkably stable to external disturbances and, for printing applications, require operating voltages much lower than in electrospray, electrowetting, or ink jet systems. [ABSTRACT FROM AUTHOR]

The present article deals with the theoretical development of the electrophoresis of core-shell structured soft particles in which the inner rigid core is decorated with a fluid and ion-permeable polymeric shell layer. Note that such a particle resembles several biocolloids (e.g., bacteria, virus, humic acid), functionalized nanoparticles, and environmental entities, to name a few. For such a structured particle, the conventional ζ -potential concept loses its meaning, and an extensive theory is required to analyze the electrohydrodynamics of the particle considering the penetration of ionized liquid across the shell layer. Note that the dielectric permittivity of the shell layer is often lower than that of the bulk aqueous medium, which induces the ion partitioning effect. Besides, in several practical situations, the hydrodynamic slipping may occur along the slipping plane. In addition, the slipping plane may not always be located along the surface of the inner core due to grafting of a polymeric shell layer along its surface, and thus, it may be assumed to be located somewhere within the surface polymeric layer. The slipping plane separates two regions with different Brinkman parameters. The region outside the slipping plane the Brinkmann screening length takes a finite value, which allows fluid flow across this region. In the region inside the slipping plane, the Brinkman parameter may practically be equal to infinity, but electrolyte ions still can penetrate this region. Considering all the physical aspects indicated above, we have proposed a simple model to study the electrophoresis of soft particles within the flat-plate regime. Based on the weak charge limit, we adopt the Debye-Hückel linearization to simplify the governing equations, and the explicit form of electrophoretic mobility is derived. Several closed-form analytic expressions are further deduced from the general mobility expressions valid under various limiting situations. We have illustrated our findings graphically to highlight the impact of pertinent parameters on the electrophoretic mobility of such a particle. In addition, we have further provided an estimate of the parametric range in which the particle may attain a zero mobility. Overall, the analytical results presented in this study will be helpful to the experimentalists to analyze their findings. [ABSTRACT FROM AUTHOR]

The present study numerically investigates the dynamics of bubble ascent under the influence of a horizontally applied electric field. We have developed an in-house electrohydrodynamics solver integrated with the open-source solver interFoam. This solver underwent meticulous validation against existing literature and was then employed for conducting simulations. Our investigation reveals the impact of the electric capillary number (C a E) on the occurrence of wobbling. Higher (C a E) values induce wobbling in various steady-state bubble shapes, including ellipsoidal, ellipsoidal cap, dimpled ellipsoidal, and bi-oblate. For the selected conductivity (R) and permittivity ratios(S), (C a E) exhibits negligible influence on bubble rising velocity. However, its effect on deformation is significant for ellipsoidal and ellipsoidal cap shapes while marginal for other configurations. (C a E) minimally affects the shape alteration of the bubble until the onset of wobbling. The overall influence of Bond number (Bo) and Reynolds number (Re) on the dynamics of bubble ascent in the presence of an electric field mirrors their impact in its absence, with one notable exception—the occurrence of wobbling. Wobbling is observed at lower Bo and Re values compared to their counterparts in the absence of an electric field. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrohydrodynamic (EHD) conduction pumping can be applied in many macroscopic devices accompanied by a high electric field intensity (106 V/m). Microscale flow generation has become increasingly important with the widespread development of thermal management devices, which are currently used to cool high heat flux sources with small surface areas and are found in a variety of electronic, controlled heat transfer, and aerospace scenarios. Additionally, the magnitude of the applied voltage can be significantly reduced in micropumping, resulting in power savings and a reliable method for flow generation. In this study, we examine the dynamic characteristics of a conduction micropump embedded within a rectangular microchannel, showing the effects of Coulombic driving forces, different channel heights, polymer elasticity, and viscosity ratios. The results show that electric power consumption can vary by two orders of magnitude for increasing channel height. As the polymer concentration increases, the maximum velocity decreases significantly and can reach 50% of that of the unadded polymer with a plunger-like distribution. The flow rate depends linearly on the polymer concentration, but exhibits non-monotonic curve with the polymer elasticity. It means that the flow rate performance of the micro-pump can be kept controllable by tuning the viscosity ratio, providing some suggestions for some regulated flow applications. [ABSTRACT FROM AUTHOR]

In the presence of stream periodicity, the electrohydrodynamic instability of three bounded liquid films with two interfaces is examined. It is considered that liquids have distinct physical characteristics and are immiscible. Under the influence of an electric horizontal field, these fluids travel through porous material. Applying the linear theory to the equations of motion and the associated boundary conditions led to two coupled Mathieu type equations with complex periodic coefficients. Approximate solutions were achieved by employing the multiple time scales technique, where the stability performance in resonance cases or not was discussed. An essential feature of this method is that transition curves are obtained analytically. It was discovered that all of the points inside these curves are unstable, whereas the regions outside of them promote the system's stability. A detailed analysis is conducted to determine how the different physical variables of the problem affect the interface stability. In the case of uniform speed, it is observed that the electric field stimulates the stability of the wave motion, while the porosity of the upper layer plays a dual role. In the presence of periodic speeds, it was observed that the speed of the top film works to destabilize the waves, while the dielectric constant gives brightness to the stability of the waves. It is also mentioned that the electric field has an important and effective role in stabilizing the fluid layers. [ABSTRACT FROM AUTHOR]

In this study of a compound droplet subjected to alternating current (AC) and direct current (DC) superposed (AC/DC) electric fields, both core and shell deformations oscillate, albeit with reduced amplitude compared to solely alternating current electric fields. As surface tension relaxes, periodic cyclic deformation ensues, with mean deformation amplifying alongside electric field amplitude. Concurrently, normal and tangential Maxwell stresses escalate with amplitude, thus augmenting interfacial surface velocities. Manipulating the offset ratio of alternating and direct current superposed electric field modulates mean deformations. Across low frequencies, stable deformation remains constant, yet a delayed onset characterizes higher frequencies. The presence of a core affects the electrohydrodynamics of the compound droplet and shell deformation, thereby mitigating phase differences between cyclic deformations. Contrasting alternating current (AC)—only fields, alternating current and direct current superposed (AC/DC) electric field scenarios exhibit heightened surface charge densities and prompter stable deformation onset. Furthermore, the direct current component magnifies mean deformations while harmonizing phase disparities between core and shell deformations. This study illuminates the intricate interplay between alternating current and direct current fields on compound droplet behavior, offering profound insight with broad implications for applications necessitating precise deformations under electric fields. [ABSTRACT FROM AUTHOR]

This article presents a sharp immersed method for simulating electrohydrodynamic (EHD) flows that involve charge evaporation. This well‐known multi‐scale, multi‐physics problem is widely used in various fields, including industry and medicine. The method adopts a fully sharp model, where surface tension and Maxwell stress are treated as surface forces and free charges are concentrated on the zero thickness liquid‐vacuum interface. Incorporating charge evaporation imposes strict restrictions on the time‐step, as the rate of evaporation sharply increases with surface evolution. To overcome this challenge, an iterative algorithm that couples the electric field and surface charge density is proposed to obtain accurate results, even with significantly large time‐steps. To mitigate the numerical residuals near the interface, which may introduce parasitic flows and cause numerical instability, an immersed interface method‐based iterative projection method for the Navier–Stokes equations is proposed, in which a traction boundary condition involving multiple surface forces is imposed on the sharp interface. Numerical experiments were carried out, and the results show that the method is splitting‐error‐free and stable. The sharp immersed method is applied to simulate the electric‐induced deformation of an ionic liquid drop with charge evaporation. The results indicate that charge evaporation can suppress the sharp development of Taylor cones at the ends of the drops. These findings have significant implications for the design and optimization of EHD systems in various applications. [ABSTRACT FROM AUTHOR]

This work introduces a novel direct current electroosmosis (DCEO) micromixer designed for rapid and efficient fluid mixing. This micromixer demonstrates excellent capability, achieving approximately 98.5% mixing efficiency within a one-second timespan and 99.8% efficiency within two seconds, all within a simple channel of only 1000 µm in length. A distinctive feature of this micromixer is its ability to generate robust and stable helical vortices by applying a controlled DC electric field. Unlike complex, intricate microfluidic designs, this work proposes a simple yet effective approach to fluid mixing, making it a versatile tool suitable for various applications. In addition, through simple modifications to the driving signal configuration and channel geometry, the mixing efficiency can be further enhanced to 99.3% in one second. [ABSTRACT FROM AUTHOR]

Abstract This article is an attempt at examining the axi-symmetric and asymmetric streaming flows described by the CSF framework. A liquid that has microfibers implanted in it, like a fiber-reinforced composite substance, is so-called CSF. It is a system that consists of an endless vertical cylindrical interface that separates the two CSF structure. The CSFs are increasingly growing significant in modern manufacturing and technology, necessitating greater research into these fluids. An axial EF acts over the cylindrical contact in addition to the influence of CSF. The VPT is employed for the sake of convenience to minimize mathematical complexity. Combining the elementary linear equations of motion and the proper linear related BCs is the major procedure of the linear technique. A collection of physically dimensionless numbers is produced using a non-dimensional process. Subsequently, the requirements for hypothetical linear stability are developed. With the aid of the Gaster's theorem, the MS is applied in computing the dispersion relationships. After carefully examining a variety of effects on the stability investigation of the system at issue, it has been shown that the system is more unstable when a porous material is present than it would be without one. The resulting axisymmetric disturbance situation is more unstable. The linear techniques are depicted throughout a number of graphs.

In fabricating functional layers, including thin-film transistors and conductive electrodes, using roll-to-roll (R2R) processing on polymer-based PET film, the instability of the slot-die coating meniscus under a high-speed web impedes functional layer formation with the desired thickness and width. The thickness profiles of the functional layers significantly impact the performance of the final products. In this study, we introduce an electrohydrodynamic (EHD)-based voltage application module to a slot-die coater to ensure the uniformity of the cross-machine direction (CMD) thickness profile within the functional layer and enable a stable, high-speed R2R process. The module can effectively control the spreadability of the meniscus by utilizing variations in the surface tension of the ink. The effectiveness of the EHD module was experimentally verified by applying a high voltage to a slot-die coater while keeping other process variables constant. As the applied voltage increases, the CMD thickness deviation reduces by 64.5%, and the production rate significantly increases (up to 300%), owing to the formation of a stable coated layer. The introduction of the EHD-based application module to the slot-die coater effectively controlled the spreadability of the meniscus, producing large-area functional layers. [ABSTRACT FROM AUTHOR]

Potato has been one of the most favorite foods with the largest production and consumption in China. However, the potato tuber with high water content can easily germinate difficult to store, leading to a serious waste of resources. Drying can be used to effectively reduce the moisture content of potatoes, and then extend the storage period for the added value. The main drying methods are hot air drying, microwave vacuum drying, freeze drying, and infrared radiation drying at present. There is also some negative impact on the color, shrinkage, and nutrient content of dried products. The existing drying has one or more defects, such as equipment, energy consumption and quality. It is necessary to explore new drying technology. Electrohydrodynamic (EHD) drying without heat can be suitable for heat-sensitive food and biological products, due to the energy saving, low cost of equipment manufacturing, simple operation, rapid control of airflow speed, and sterilization. There was also excellent retention of the color, nutrient composition and shape of the material. However, it is still lacking on systematic studies on the drying and physicochemical characteristics of potatoes using EHD drying. In this study, the potatoes were dried by electrohydrodynamic drying. A systematic measurement was then carried out of the moisture content, drying rate, Rehydration ratio and effective moisture diffusion coefficient of potatoes under different drying voltages. The effects of electrohydrodynamic drying on the molecular structure, chemical composition and water transport of potatoes were also investigated by infrared spectroscopy and low-field nuclear magnetic resonance. Corona discharge was generated by a highvoltage electric field during drying. The voltage and current waveforms were plotted to obtain the outstanding filamentary discharge in half of the cycle. The higher the voltage in a single cycle was, the higher the discharge frequency and current amplitude were. The uneven discharge promoted the discharge, and then inhibited the discharge around, indicating positive feedback. High-voltage electric field discharge produced N+, N2+, O2-, and OHions. A large number of neutral particles were mixed to blow away from the needle electrode, and then form the ionic wind. As such, the ionic wind was also attributed to the main mechanism of electrohydrodynamic drying. A falling-rate period was then found when the electrohydrodynamic drying was acted mainly on the surface of the potatoes. The drying rate increased with the increase of voltage, whereas, the increment gradually decreased. Electrohydrodynamic drying significantly increased the effective moisture diffusion coefficient and Rehydration ratio of potatoes. The highest average drying rate, effective moisture diffusion coefficient and rehydration ratio were 0.922 8 g/(g·h), 2.265 3×10-10 m 2 /s, and 4.78 at 30 kV voltage. There were generally similar positions of characteristic peaks in the infrared spectra under different drying voltages. The characteristic peak intensity at 22 kV was the largest. Potato protein was dominated by β-sheet structure. The β-sheet structure shared an increasing trend with the increase in voltage. Thus, electrohydrodynamics led to the transformation of the protein's secondary structure from the order to the disorder. The internal structure of the potato was destroyed to reduce the binding force of less mobile water, particularly for the improved fluidity of free water. The migration and removal of three kinds of water were promoted in the potato, resulting in a decrease in water content. Infrared spectroscopy analysis showed that there was no significant change in the functional groups after drying. The finding can also provide the experimental and theoretical reference for electrohydrodynamic drying in potato processing. [ABSTRACT FROM AUTHOR]

This article is an attempt at examining the axi-symmetric and asymmetric streaming flows described by the CSF framework. A liquid that has microfibers implanted in it, like a fiber-reinforced composite substance, is so-called CSF. It is a system that consists of an endless vertical cylindrical interface that separates the two CSF structure. The CSFs are increasingly growing significant in modern manufacturing and technology, necessitating greater research into these fluids. An axial EF acts over the cylindrical contact in addition to the influence of CSF. The VPT is employed for the sake of convenience to minimize mathematical complexity. Combining the elementary linear equations of motion and the proper linear related BCs is the major procedure of the linear technique. A collection of physically dimensionless numbers is produced using a non-dimensional process. Subsequently, the requirements for hypothetical linear stability are developed. With the aid of the Gaster's theorem, the MS is applied in computing the dispersion relationships. After carefully examining a variety of effects on the stability investigation of the system at issue, it has been shown that the system is more unstable when a porous material is present than it would be without one. The resulting axisymmetric disturbance situation is more unstable. The linear techniques are depicted throughout a number of graphs. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of the melting of dielectric material in a rectangular cavity under the effect of electrohydrodynamics (EHD). First, phase-change modeling is implemented to simulate the melting performance of paraffin wax without EHD under constant temperature boundary conditions until a steady-state condition is achieved. Next, the whole set of coupled EHD equations is introduced to the model, with the Coulomb force using a Heaviside function for charge injection being the only electrical body force considered. Finally, the numerical model is implemented using the finite element method to solve for the electric field, flow field, temperature field, and charge transport. The numerical results show that, under the effect of EHD, melting continues due to the generation of electroconvection cells in the liquid phase-change material and the flow field manifests as two symmetric rotational cells generated between every two successive electrodes. The flow field causes the redistribution of the temperature field in the liquid bulk, which enhances the heat transfer. Melting continues until a steady-state condition is almost reestablished after about one hour. The enhancement factor, defined as the ratio of the EHD melt thickness to the steady-state melt thickness without EHD, is 2.33 at 6 kV applied voltage. [ABSTRACT FROM AUTHOR]

As summarized by Papageorgiou [Annu. Rev. Fluid Mech., 51 (2019), pp. 155-187], a strong normal electric field can cause instability of the interface in a hydrodynamic system. In the present work, singularities arising in electrocapillary-gravity waves on a dielectric fluid of finite depth due to an electric field imposed in the direction perpendicular to the undisturbed free surface are investigated. In shallow water, for a small-amplitude periodic disturbance in the linearly unstable regime, the outcome of the system evolution is that the gas-liquid interface touches the solid bottom boundary, causing a rupture. A quasi-linear hyperbolic model is derived for the long-wave limit and used to study the formation of the touch-down singularity. The theoretical predictions are compared with the fully nonlinear computations by a time-dependent conformal mapping for the electrified Euler equations, showing good agreement. On the other hand, a nonlinear dispersive model system is derived for the deep-water scenario, which predicts the blowup singularity (i.e., the wave amplitude tends to infinity in a finite time). However, when the fluid thickness is significantly large, one can numerically show the self-intersection nonphysical wave structure or 2/3 power cusp singularity in the full Euler equations. [ABSTRACT FROM AUTHOR]

Motivated by the use of magnetohydrodynamic devices in fluid dynamic flow control research, the current work experimentally studied the actuation mechanism and the resulting aerodynamic interactions of magnetically driven low-current arc-plasma discharges. The investigation was conducted in the context of boundary-layer interactions in low-speed crossflow conditions through the use of coaxial and v-shaped geometries. Time-averaged velocity field measurements showed that the toroidal region of vorticity induced by the coaxial geometry in quiescent air resulted in the formation of a horseshoe vortex in crossflow. Similarly, the v-shaped actuator resulted in the formation of streamwise vortices. The resulting boundary layers had s-shaped streamwise velocity profiles as measured in the wall-normal direction characteristic for the flow downstream of a conventional vortex generator pair, due to the three-dimensional mixing induced by coherent vortex structures. A simplified model based on intermolecular momentum transfer through collisions is proposed to explain the fundamental discharge-air interactions and the induced flowfields. These results inform the applications of various magnetically driven discharges in the field of aerodynamic flow control. [ABSTRACT FROM AUTHOR]

In this work, we present a two-phase electro-magneto-fluid dynamics (EMFD) model that merges electromagnetics and fluid dynamics. The model is suitable for use in computational fluid dynamics (CFD) software and was incorporated into OpenFOAM® after deriving appropriate equations that bypassed certain limitations of the software. Currently, there is lack of even single-phase EMFD models that can be incorporated into CFD software; however, simpler models from electrohydrodynamics (EHD) and magnetohydrodynamics (MHD) are being implemented although they have certain approximations that can limit their applicability. We conclude that the derived EMFD model is applicable, and show its quality by implementing it and analyzing the results. We use cases with a droplet and the electrospinning process for verification. The drop deformations obtained were closer to analytical predictions than in the literature for two EHD models, but some oscillations were observed. We compared one simulation to the prediction of an analytical equation from MHD, and good agreement was shown. Finally, we simulate the electrospinning process, and the results were very close to the analytical predictions. We conclude that the implementation can be used for both EHD and MHD cases. [ABSTRACT FROM AUTHOR]

The possibility of estimating the ionization parameters of high-temperature gas mixtures formed as a result of combustion processes is considered on the basis of the current–voltage characteristics measured using electrodes that generate an external electric field in the media under consideration. [ABSTRACT FROM AUTHOR]

Formation of highly viscous droplets and liquid bridges under the influence of electric fields is widely used in material preparation, food processing, inkjet printing and 3D (three-dimensional) printing. To investigate the formation of droplets and liquid bridges, a visual experimental platform is designed and constructed. A non-uniform electric field is constructed using a metal capillary and a copper pole plate. By varying the voltage, capillary diameter and liquid volume flow rate, the formation of silicone oil droplets and liquid bridges is investigated. The influence of electric forces to the coiling effect of viscous fluids is researched, which has not been thoroughly investigated in previous research. The results verify that at low volume flow rates and small pipe diameters, the silicone oil formation pattern is in the droplet state. As the voltage increases, the droplet formation period decreases. When the voltage is gradually increased at higher volume flow rates, the silicone oil changes from the initial liquid bridge to the droplet. This experimental phenomenon demonstrates that the electric field can alter the instability of the jet. In the case of small volume flow rates and large pipe diameter, the droplet formation state changes from droplet mode to multi-strand jet mode after the voltage is increased to a certain level. At large pipe diameters and large volume flows rates, the liquid bridge mode with a rope coiling effect occurs due to the highly viscous nature of the silicone oil, but the rope coiling effect disappears after a certain voltage is applied. [ABSTRACT FROM AUTHOR]

Copyright of Structural Integrity & Life / Integritet i vek Konstrukcija is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hydrogel microparticles (HMPs) stand out as promising entities in the realm of bone tissue regeneration, primarily due to their versatile capabilities in delivering cells and bioactive molecules/drugs. Their significance is underscored by distinct attributes such as injectability, biodegradability, high porosity, and mechanical tunability. These characteristics play a pivotal role in fostering vasculature formation, facilitating mineral deposition, and contributing to the overall regeneration of bone tissue. Fabricated through diverse techniques (batch emulsion, microfluidics, lithography, and electrohydrodynamic spraying), HMPs exhibit multifunctionality, serving as vehicles for drug and cell delivery, providing structural scaffolding, and functioning as bioinks for advanced 3D-printing applications. Distinguishing themselves from other scaffolds like bulk hydrogels, cryogels, foams, meshes, and fibers, HMPs provide a higher surface-area-to-volume ratio, promoting improved interactions with the surrounding tissues and facilitating the efficient delivery of cells and bioactive molecules. Notably, their minimally invasive injectability and modular properties, offering various designs and configurations, contribute to their attractiveness for biomedical applications. This comprehensive review aims to delve into the progressive advancements in HMPs, specifically for bone regeneration. The exploration encompasses synthesis and functionalization techniques, providing an understanding of their diverse applications, as documented in the existing literature. The overarching goal is to shed light on the advantages and potential of HMPs within the field of engineering bone tissue. [ABSTRACT FROM AUTHOR]

Melt electrowriting (MEW) is a young and promising additive manufacturing technology for producing high‐precision scaffolds. In this study, we develop an intuitive visualization system enabling users to measure MEW jet diameters along the spinline without programming knowledge. The digital measurement adopts the same theory as our reported manual measurement. The maximum error between the digitally and manually measured data is smaller than 9%, suggesting that the open‐source system developed here is reliable in measuring jet diameters. [ABSTRACT FROM AUTHOR]

The nonlinear instability of a planar interface between two overlapping Rivlin-Ericksen viscoelastic liquids, in the occurrence of fine dust and vertical electric fields throughout permeable media, and the influence of surface tension is studied. The prototype structure is assumed to be a two-dimensional groundwork for the sake of simplicity. The growing approval of several disciplines of practical physics and technology serves as motivation for analyzing this problem. Using viscous potential theory, the mathematical procedure is condensed. To properly control electro convection in liquid crystals, which is widely used in various displays technologies, it was crucial to have a thorough comprehension of stability. Gaining understanding of the behavior of viscoelastic fluids at interfaces was crucial in polymer manufacturing industries. Employing the linear equations of movement with the suitable nonlinear bounder circumstances forms the basis of the considered nonlinear technique. A nonlinear partial differential equation that evaluates the interface movement is the objective of the process. Since linear stability has frequently been investigated, the present situation will be constructed only in the nonlinear sense, where a number of dimensionless physical numerals are achieved. The non-perturbative methodology is used to accomplish the nonlinear standards. The main idea behind the novel performance is to convert an ordinary nonlinear ordinary differential equation into a linear one. The new technique differs from the conventional perturbation methods in that it may be used to exactly and correctly analyze the behavior of the strong nonlinear aspects of the interface displacement. This innovative method is established by using He's frequency formula. Using the nonlinear distinguishing equation, the special situation of the real and the complex coefficients is accomplished. It was observed that the instability zone expands as the electric field, porosity of porous medium, and density ratio of two fluids rise. The stability configuration is enhanced by the viscoelasticity parameter, Bond number, and ratio of kinematic viscoelasticity.

Ionic wind, produced by electrohydrodynamic (EHD) processes, holds promise for efficient airflow generation using minimal power. However, practical applications have been limited by relatively low flow rates. This study introduces a novel prototype device designed to amplify ionic wind-generated flow rates by leveraging the Coanda effect. This scalable device features a unique needle electrode configuration, optimized geometry, and operating parameters to enhance flow rates and reduce electrical energy consumption. The experimental investigation encompasses two ground electrode configurations as collectors to evaluate velocity profiles within an extended wind channel setup. The analysis revealed that the rod collector arrangement slightly outperformed the plate collector regarding airflow rate and efficiency. Notably, a flow rate of up to 7.5 m3 h-1 was attained with an energy input of less than 2 W at 30 kV and a flow rate of 5 m3 h-1 within the optimal voltage range of 15–20 kV, requiring around 0.5 W. The findings indicate that a decrease in the number of needle emitters has a relatively negligible impact on the airflow rate, suggesting an opportunity to design more efficient devices with fewer needles. To complement the experimental results, a computational fluid dynamics (CFD)--based digital mirror was utilized to obtain deeper insights into the flow field patterns. The use of the CFD model confirmed that our device can increase flow rates by a factor of around three. The findings of this research have far-reaching implications for developing next-generation ionic wind generators, particularly in sustainable fluid flow engineering. By confirming the effectiveness of amplified ionic wind-based airflow, we provide a clear path for this technology to contribute to cleaner production practices across various industries. Ionic wind amplifiers show potential in applications requiring precise airflow control, such as data centers, cleanrooms, sterilization, or drying processes, where removing excess heat or maintaining specific conditions is essential.

A focused, brief review on the issue of needleless electrohydrodynamic (EHD) methods for making submicron fibers and particles is presented. Advantages over conventional EHD methods, especially on the issue of production scale, are discussed. An overview of key, entry-point patent, and journal literature are offered to assist the materials processing engineer in the equipment design selection. [ABSTRACT FROM AUTHOR]

This study investigates the effects of electrohydrodynamic (EHD) drying technology on the drying kinetics, microstructure, quality, and nutritional components of carrots, along with conducting experiments on EHD drying under different voltage gradients. The experimental results showed that EHD drying technology could significantly increase the drying rate and the effective moisture diffusion coefficient. Within a certain range, the drying rate was directly proportional to the voltage. When the range was exceeded, the increase in voltage had a minimal effect on the drying rate. In terms of quality, the EHD drying group's color, shrinkage rate, and rehydration performance were superior to the control group, and different voltages had no significant effect on the shrinkage rate and rehydration performance. The retention of carotenoids in the EHD drying group was 1.58 to 2 times that of the control group. EHD drying had a negative impact on the total phenolic content and vitamin A content of dried carrot slices. Based on the results of infrared spectroscopy and scanning electron microscopy (SEM), the dehydrated carrot slices showed wrinkling due to water loss, with numerous pores, a generally intact structure, and retained functional groups. EHD drying had a significant impact on the secondary structure of proteins, where an increase in voltage led to an increase in disordered structure, with a smaller proportion of disordered structure in the lower voltage group compared to the control group, and a similar proportion of disordered structure between the higher voltage group and the control group. Results from low-field nuclear magnetic resonance (NMR) showed that EHD drying could retain more bound water compared to the control group, with the best retention of cellular bound water at a voltage of 26 kV and the best retention of cellular immobilized water at a voltage of 38 kV, indicating the superiority of EHD drying in preserving cellular structure. This study provided a theoretical basis and experimental foundation for the application of electrohydrodynamic drying technology to carrot drying, and promoted the practical application of EHD drying technology. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) printing is a micro–nano printing technology based on the principles of electric field and fluid dynamics. It is characterized by high resolution, high precision, and high speed, applied to various materials, including metals, ceramics, and organic materials. Compared with traditional printing technologies, EHD printing offers advantages such as low manufacturing cost, simple process, and direct fabrication, making it highly promising in the field of micro–nano manufacturing. Polyethylene oxide (PEO) is a highly water‐soluble polymer that has been widely used in various fields due to its low toxicity and ease of processing. In this study, a finite element simulation model was developed using simulation software to simulate and analyze the mechanisms of focused jetting and deposition of PEO solution under an electric field. Based on the principles of electrohydrodynamics, a self‐built EHD printing system was used to investigate the influence of different solution mass fractions and printing parameters on fiber formation, and the optimal process window of EHD printing PEO solution was obtained. Ultimately, ordered deposition of fiber lines ranging from 1.761 to 6.093 μm was achieved. The simulation results were consistent with the experimental results, validating the effectiveness of the established model in guiding jetting outcomes. Highlights: Independently building a low‐cost electrohydrodynamic (EHD) printing system.Finite element simulation of EHD printing process.Mechanism analysis of PEO solution jetting and deposition.Optimal process window for PEO solution EHD printing.Influence of key process parameters on fiber forming width. [ABSTRACT FROM AUTHOR]

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There is growing interest in the use of micro-sized hydrogels, including bioactive signals, as efficient platforms for tissue regeneration because they are able to mimic cell niche structure and selected functionalities. Herein, it is proposed to optimize bioactive composite microgels via electrohydrodynamic atomization (EHDA) to regenerate the dentin–pulp complex. The addition of disodium phosphate (Na2HPO4) salts as mineral precursors triggered an in situ reaction with divalent ions in solution, thus promoting the encapsulation of different amounts of apatite-like phases. Morphological analysis via image analysis of optical images confirmed a narrow distribution of perfectly rounded particles, with an average diameter ranging from 223 ± 18 μm to 502 ± 64 μm as a function of mineral content and process parameters used. FTIR, TEM, and EDAX analyses confirmed the formation of calcium phosphates with a characteristic Ca/P ratio close to 1.67 and a needle-like crystal shape. In vitro studies—using dental pulp stem cells (DPSCs) in crown sections of natural teeth slices—showed an increase in cell viability until 14 days, recording a decay of proliferation at 21 days, independent on the mineral amount, suggesting that differentiation is started, as confirmed by the increase of ALP activity at 14 days. In this view, mineralized microgels could be successfully used to support in vitro osteogenesis, working as an interesting model to study dental tissue regeneration. [ABSTRACT FROM AUTHOR]

This comprehensive review paper focuses on the intricate physics of microfluidics and their application in micromixing techniques. Various methods for enhancing mixing in microchannels are explored, with a keen emphasis on the underlying fluid dynamics principles. Geometrical micromixers employ complex channel designs to induce fluid–fluid interface distortions, yielding efficient mixing while retaining manufacturing simplicity. These methods synergize effectively with external techniques, showcasing promising potential. Electrohydrodynamics harnesses electrokinetic phenomena like electroosmosis, electrophoresis, and electrothermal effects. These methods offer dynamic control over mixing parameters via applied voltage, frequency, and electrode positioning, although power consumption and heating can be drawbacks. Acoustofluidics leverages acoustic waves to drive microstreaming, offering localized yet far-reaching effects. Magnetohydrodynamics, though limited in applicability to certain fluids, showcases potential by utilizing magnetic fields to propel mixing. Selecting an approach hinges on trade-offs among complexity, efficiency, and compatibility with fluid properties. Understanding the physics of fluid behavior and rationalizing these techniques aids in tailoring the most suitable micromixing solution. In a rapidly advancing field, this paper provides a consolidated understanding of these techniques, facilitating the informed choice of approach for specific microfluidic mixing needs. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) processes are promising techniques for manufacturing nanoscopic products with different shapes (such as thin films, nanofibers, 2D/3D nanostructures, and nanoparticles) and materials at a low cost using simple equipment. A key challenge in their adoption by nonexperts is the requirement of enormous time and resources in identifying the optimum design/process parameters for the underlying material and EHD system. Machine learning (ML) has made exciting advancements in predictive modeling of different processes, provided it is trained on high‐quality datasets at appropriate volumes. This article extends the suitability of such ML‐enabled approaches to a new technological domain of EHD spraying and drop‐on‐demand printing. Different ML models like ridge regression, random forest regression, support vector regression, gradient boosting regression, and multilayer perceptron are trained and their performance using evaluation metrics like RMSE and R2_score is examined. Tree‐based algorithms like gradient boosting regression are found to be the most suitable technique for modeling EHD processes. The trained ML models show substantially higher accuracy (average error < 5%) in replicating these nonlinear processes as compared to previously reported scaling laws (average error ≈ 42%) and are well suited for predictive modeling/analysis of the underlying EHD system and process. [ABSTRACT FROM AUTHOR]

This work introduces a novel direct current electroosmosis (DCEO) micromixer designed for rapid and efficient fluid mixing. This micromixer demonstrates excellent capability, achieving approximately 98.5% mixing efficiency within a one-second timespan and 99.8% efficiency within two seconds, all within a simple channel of only 1000 µm in length. A distinctive feature of this micromixer is its ability to generate robust and stable helical vortices by applying a controlled DC electric field. Unlike complex, intricate microfluidic designs, this work proposes a simple yet effective approach to fluid mixing, making it a versatile tool suitable for various applications. In addition, through simple modifications to the driving signal configuration and channel geometry, the mixing efficiency can be further enhanced to 99.3% in one second.

The drying characteristics, rehydration capacity, color, infrared spectra and volatile components of iron stick yam slices were investigated under different alternating current (AC) voltages (13, 17, 21 kV), hot air drying (HAD) (60 °C) and natural drying (AD) by electrohydrodynamic (EHD) drying and HAD experimental devices. The results showed that slices of iron stick yam dried the quickest with HAD, which also had the fastest drying rate; while drying the slices of iron stick yam with EHD led to a better rehydration capacity, higher brightness L* and whiteness, a more stable protein secondary structure, and a greater variety and content of volatile components compared with AD and HAD. These finding indicated that EHD is a more promising method for drying iron stick yam.

Soft robots are able to safely operate in a dynamically evolving or highly unstructured environment by virtue of their inherited compliance. Among the available actuation methods for soft robotics, fluid‐driven is frequently preferred due to holistic design considerations that enable multipurpose yet straightforward mechanical solutions to complicated issues. The motion of a soft fluid‐driven robotic system usually relies on the flow of its internal fluid, however, existing fluid pumps only enable a single linear flow, which severely hinders the integrated multifunctional design of soft robots. Herein, a class of liquid manipulator is proposed based on electrohydrodynamic (EHD) effect, which consists of a flexible substrate with a printed planar electrode pattern. By streamlining the electric field distribution via electrode pattern, the liquid manipulator can manipulate the fluid flow, allowing fluid to perform multiple movement behaviors, including tangential, radial, and linear motions. These liquid manipulators are fabricated by printing planar electrode patterns onto flexible substrates using the digital printing method, in which both the printed electrodes and substrate are flexible and bendable. These liquid manipulators are flexible, fast‐response, thin, lightweight, and scalable, which can be easily embedded into soft fluidic systems with insignificant footprint and weight and actuate their rapid movements. Three liquid manipulators are embedded into a continuously rotating motor, focus‐tunable liquid lens, and soft linear actuator to achieve their multiple motions, i.e., continuous rotation, radial motion, and linear motion, illustrating broad potential of liquid manipulators in soft robotic systems. [ABSTRACT FROM AUTHOR]

In the numerical simulation of droplet breakup under electric field, the meshless method has inherent advantages, however the enforcement of boundary conditions is challenging. Therefore, a coupling method of smoothed particle hydrodynamics(SPH) method and finite volume method(FVM) is proposed to investigate the breakup behavior of leaky dielectric droplet under half-sinusoidal wave electric field. The present numerical method is validated and is well consistent with results in the literature. The effects of electric field strength and droplet viscosity on droplet breakup are mainly discussed, and three different modes of droplet breakup are revealed: conical-conical angle breakup, dumbbell-dimple breakup and cylindrical-non tip breakup. The regions of these three breakup modes are plotted in the breakup phase diagram of electric capillary number and viscosity ratio. The numerical experiments also demonstrate that the droplet breakup mode depends on the velocity field and pressure field of the droplet and the surrounding fluid. [Display omitted] • The SPH method and the FVM were coupled in this work. • The breakup of droplet under electric field is simulated with the proposed method. • Three different modes of droplet breakup are revealed. • The regions of the three breakup modes are plotted. [ABSTRACT FROM AUTHOR]

In this paper, a multi-physics field coupled model of electric, flow and particle fields was constructed by COMSOL to compare the effects of three different corrugated dust collector plates on electric field distribution, airflow field, particle trajectories and dust removal efficiency in an electrostatic precipitator, and to compare them with a conventional electrostatic precipitator with a parallel plate structure. The results indicated that the corrugated dust collection plate influenced the electric field within the ESP channel, while the wire plate spacing directly affected the size and distribution of space charge density. Furthermore, the corrugated dust collection plate also affected the EHD flow within the channel, with the D2-ESP and D3-ESP being the most strongly influenced by the ionic wind. By comparing the dust removal efficiency of the four ESPs, we found that D2-ESP has the highest dust removal efficiency, followed by D3-ESP, then Flat-ESP, and finally D1-ESP. The ranking order of the four ESPs' dust removal efficiency is consistent with the ranking order of the space charge density within the four ESP channels, which shows that the size of the space charge density directly affects the dust removal efficiency of ESPs. Numerical simulation results show that the change of wire plate spacing is the main reason why corrugated ESP affects the dust removal efficiency of electrostatic precipitators. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) drying refers to the removal of water from a wet material exposed to a strong electric field due to the aerodynamic action of so-called "ionic" or "corona" wind. This action disturbs the gas boundary layer at the material interface, decreasing convective mass transfer resistance and promoting convective mass transfer from the material. The advantage of EHD technology is the direct use of electric energy for water evaporation at ambient temperature, and therefore it could be used for drying heat-sensitive foods. Due to zero heat generation, the energy consumption of EHD drying is very low, about 20-25 times smaller than equivalent thermal drying. Lab-scale research confirmed multiple benefits of this innovative technology, such as high drying rate, high energy efficiency, premium product quality, no GHG emissions, and low capital and operational costs. This paper contributes to the application of innovative EHD drying in combination with other drying technologies to improve the overall efficiency of heat-sensitive food drying. This application is illustrated with the experimental results of EHD drying of apple slices. The clean and eco-friendly nature of EHD technology in conjunction with premium product quality makes it a good alternative for future food engineering. [ABSTRACT FROM AUTHOR]

The interfacial tension is a crucial property of two-phase immiscible liquid. However, many researchers are not aware about the fact that its value is far from being constant for many pairs of liquids. The paper presents the measurements of interfacial tension time-dependencies for various oils against distilled water and assesses how it affects electrohydrodynamic processes in two-phase immiscible liquids. Primary results were obtained using an optical tensiometer (the pendant drop method). Further on, several computations of droplet electrodeformation were performed and compared to the relevant experimental data to independently check the reliability of the measurements. It was found that the decrease with time of the interfacial tension against water is specific for a lot of liquids, in particular, for many vegetable oils and even for transformer oils after it being used in power transformers. The change of the interfacial tension with time is shown to be a realistic cause for the emergence of the so-called cone-dimple mode of electrocoalescence, which was earlier reported in experimental studies. The paper includes experimentally measured properties (that need to be specified in numerical models) for many liquids. [ABSTRACT FROM AUTHOR]

Electroadhesive surface haptic touchscreens can help augment user experiences by providing tactile effects. The electrode layout in current commercialized designs has separated electrodes for the sensing and actuating functions. During regular use, it is observed that fingerprint residue preferentially deposits on the actuating electrodes far more than the sensing electrodes, which makes the underlying electrode pattern apparent and is highly undesirable for touchscreen users. To address this issue, various physical phenomena (electrohydrodynamic deformation, capillary bridge stabilization, electrowetting, and electrophoretic deposition) are investigated to understand the mechanism. Through experimentation, multiphysics modeling, and surface characterization, it is found that the root cause can be attributed to two mechanisms occurring in the actuating regions: 1) electrohydrodynamic deformation of sebum droplets attached to the finger valleys leading to the formation of additional capillary bridges and residual droplets on the screen surface after their rupture, and 2) electric field‐induced stabilization of sebum capillary bridges existing between the finger ridges and the screen, leading to the coalescence and formation of larger‐sized droplets. The developed model can then be used to address the issue during the screen design process. An example of using the model to explore the impact of changes in screen oleophobicity is shown. [ABSTRACT FROM AUTHOR]

A comprehensive numerical model has been developed, which is capable of predicting the spreading of a high-speed yttria-stabilized zirconia (YSZ) droplet with solidification microstructure formation under a horizontal electric field in plasma spraying processes. The numerical model entails the explicit finite difference solution of the Navier–Stokes equations and the energy balance equation, coupled with the Cahn–Hilliard equation to track the liquid–gas two-phase interface and with a phase field model for solidification microstructure formation involving polycrystalline growth. The electric force is added as a source term in the Navier–Stokes equations, and the fluids are assumed to be perfect dielectrics. The in-house code is written in Fortran and run in parallel. The results reveal that the retracting process could be completely inhibited using a horizontal electric field and that solidification time is greatly reduced. A new mechanism to suppress droplet breakup/splash could be realized, featuring reduction of the rising angle the spreading front makes with a substrate. All the cases show columnar grains within a splat. Besides, the model is validated against experimental results, with gratifying agreement achieved. [ABSTRACT FROM AUTHOR]

The electrohydrodynamic plane Couette–Poiseuille flow instability of two superposed conducting and dielectric viscous incompressible fluids confined between two rigid horizontal planes under the action of a normal electric field and pressure gradient through Brinkman porous medium has been analytically investigated. The lower plane is stationary, while the upper one is moving with constant velocity. The details of the base state mathematical model and the linearized model equations for the perturbed state are introduced. Following the usual procedure of linear stability analysis for viscous fluids, we derived two non-dimensional modified Orr–Sommerfeld equations and obtained the associated boundary and interfacial conditions suitable for the problem. The eigenvalue problem has been solved using asymptotic analysis for wave numbers in the long-wavelength limit to obtain a very complicated novel dispersion relation for the wave velocity through lengthy calculations. The obtained dispersion equation has been solved using Mathematica software v12.1 to study graphically the effects of various parameters on the stability of the system. It is obvious from the figures that the system in the absence of a porous medium and/or electric field is more unstable than in their presence. It is found also that the velocity of the upper rigid boundary, medium permeability, and Reynolds number have dual roles on the stability on the system, stabilizing as well as destabilizing depending on the viscosity ratio value. The electric potential, dielectric constant and pressure gradient are found to have destabilizing influences on the system, while the porosity of the porous medium, density ratio and Froude number have stabilizing influences. A depth ratio of less than one has a dual role on the stability of the system, while it has a stabilizing influence for values greater than one. It is observed that the viscosity stratification brings about a stabilizing as well as a destabilizing effect on the flow system. [ABSTRACT FROM AUTHOR]

One of the possible mechanisms of the interaction of a bounded combustion region (flame) with an applied electric field is considered. The investigation is based on application of the electrohydrodynamics (EHD) methods to describe chemically reacting multicomponent nonequilibrium partially ionized gas mixtures. It is shown that zones of space electric charge are formed in the neighborhood of the flame boundaries under certain conditions. These zones can be affected by the electric field. The nature of modification of these zones under the influence of the electric field is investigated. [ABSTRACT FROM AUTHOR]