Droplet generation in electrohydrodynamic (EHD) drop-on-demand (DoD) printing is governed by two competing electrostatic mechanisms, the instantaneous magnitude of Maxwell stress at the liquid–air interface and the transient accumulation of surface charge over the finite pulse duration. Despite the physical coupling, these mechanisms have not previously been delineated within a unified dimensionless framework. This work introduces two governing parameters, the Electric Bond number BoE, representing the ratio of electrostatic stress to capillary pressure and the pulse charging parameter Λ, representing the ratio of pulse duration to the charge relaxation time, to characterise the transition between field-dominated and duration-dominated droplet formation regime. A full 24 factorial numerical simulation campaign varies voltage amplitude, pulse width, duty cycle, and nozzle–substrate distance across three fluids spanning eleven orders of magnitude in Λ. Simulations employ an axisymmetric Coupled Level-Set/Volume-of-Fluid (CLSVOF) electrohydrodynamic model with full Maxwell stress coupling. A clear sensitivity reversal from voltage-dominated to pulse-width-dominated control is observed at Λ ≈ 1, consistent with the theoretical regime boundary derived from the exponential saturation of interfacial charge. Within each fluid, droplet diameter follows consistent power-law scaling with BoE (local exponents ranging from −0.36 to −1.29 depending on fluid and regime). Pooling the dimensionless diameter D* = D/R across all three fluids against BoE gives a substantial partial collapse (D* ∝ BoE−0.69, R2 = 0.83); residual scatter (mean 26%, up to a factor of 2 for the most duration or saturation-influenced points) indicates viscosity and flow-rate differences between fluids likely also play a role. Response surface models based on the factorial dataset achieve R2 > 0.92 for all fluids.
This study presents the design, theoretical modeling and laboratory calibration of an electrostatic particulate matter monitor developed for regional haze surveillance in Northern Thailand. In place of light scattering, the instrument uses unipolar diffusion charging with a Faraday cup electrometer, combined with a custom inertial impactor for PM2.5 size selection and a PID-regulated flow system that fixes the aerodynamic cut-point. The impactor collection efficiency was measured at ten monodisperse PSL diameters, giving d50 = 2.23 ± 0.02 μm from a sigmoidal fit and a cut-point sharpness of σg = 1.40 by interpolation of the measured points, 1.39 from the same fit; convolving the fitted penetration curve with the accumulation-mode distribution measured previously at the site, together with an assumed coarse mode of up to a fifth of the PM2.5 mass, gives a net size-selection bias of only −0.1% to −1.4%. Laboratory comparison against a TEOM 1405DF over 12 to 1148 μg m−3 gave a Pearson correlation of 0.997 and an ordinary least-squares slope of 0.929 ± 0.024, with Bland–Altman limits of agreement of −23% to +20%. Two field deployments were carried out. A 44.9-h record at near-background concentrations, 8.3 to 23.2 μg m−3 at the reference, agreed with it in the mean to 0.01 μg m−3. A continuous 72-h deployment during the March 2025 haze season spanned 14 to 222 μg m−3, gave r = 0.939, agreed with the reference to within 0.5 μg m−3 on each of three 24-h means and showed no saturation at the peak; the mean difference was +2.1% with a 95% confidence interval that includes zero, while the limits of agreement for individual hourly values were −36% to +40%. The instrument is therefore validated at the 24-h averaging time on which the ambient standard is defined rather than at hourly resolution.
Electrostatic precipitators (ESPs) are widely used for industrial particulate control but exhibit limited efficiency for PM2.5, especially submicron particles. This study proposes an enhanced ESP with auxiliary electrodes and magnetic field. A multi-physics numerical model evaluated synergistic effects across electrode spacings of 0.018–0.044 m under the selected model assumptions and operating conditions. Magnetic effects were more pronounced for particles <0.5 μm. Spacing analysis reveals a non-monotonic trend for auxiliary electrodes and monotonic decline in magnetic enhancement with wider gaps within the investigated parameter range. These findings guide high-efficiency ESP designs for ultrafine particulate control.
This article explicitly investigates the heat transfer characteristics through bi-phase flow in an inclined channel under different constraints. Two separate multiphase suspensions have been formulated theoretically by employing linear and exponential Phan–Thien–Tanner (PTT) fluid models. Gold and silver metallic particles are chosen for the disperse phase. An analytical solution is obtained by solving the set of differential equations. A comprehensive investigation is carried out and validated with the existing literature for the limiting case via parametric study and computational data. The investigation infers that higher thermal conductivity is achieved for the case of gold & Phan–Thien–Tanner suspension.
Controlling the potential on floating targets Vtarget is critical for plasma–surface interactions in atmospheric pressure plasma jets (APPJs). In this work, the interaction between an atmospheric-pressure helium plasma jet and a floating metallic target was investigated experimentally. The plasma jet is driven by a bipolar voltage pulse with adjustable duty ratio dr. The results show that the target potential increases from negative to positive with increase of the duty ratio. Potentials close to 0 V were obtained by adjusting dr under different peak-to-peak voltages. The bipolar pulse with an adjustable duty ratio is an effective method to control the potential on the target. The charging time and the discharge intensity of the plasma jet are important factors in controlling the target potential.
To investigate the electrostatic ignition mechanisms of polymer materials in pure oxygen, an experimental platform was established to study Nylon 1010 ignition under pure oxygen at 0.1 MPa to 0.5 MPa. Using high-speed imaging, three ignition modes were identified: Arc-thermal erosion ignition, molten-spatter attachment ignition, combined-effect ignition. Experimental results reveal the competitive effects of spark energy (E), electrode gap (d), oxygen pressure (p), and their combined effects on ignition mode transition. Increasing E promotes the transition from Mode I to Mode II, whereas enlarging d exhibits the opposite trend. A higher oxygen pressure p significantly enhances the dominance of Mode III.
Wearable self-powered sensors offer new opportunities for rehabilitation monitoring and chronic pain management. Here, a surface-regulated polyaniline/silver nanowire/poly(vinyl alcohol) hydrogel triboelectric nanogenerator (SPPA-TENG) is developed for assessing rehabilitation quality in chronic nonspecific lower back pain. A bilayer S-PPA hydrogel acts as a flexible conductive electrode, with nylon and polyvinyl chloride as the triboelectric pair. Freeze-induced crosslinking, conductive nanoparticles, and ionic surface densification enhance mechanical strength and electrical stability. The optimized device delivers 152.2 V, 36.7 μA, and 84.1 nC, and remains stable under frequency, strain, and cycling tests. Lumbar-mounted sensing enables trunk-motion tracking and distinguishes healthy from pathological patterns.
To address the issue of insufficient fuel atomization quality in the afterburner of aircraft engines, this paper designs a plasma-excited fuel injection rod structure based on a sliding arc plasma and conducts a systematic experimental study of its discharge characteristics and atomization performance. Under key operating conditions such as input voltage (Uin), air flow rate (qair), and cross-flow pressure (Pair), the study analyzes the influence of output voltage (Uout), discharge morphology, and power characteristics on the spray cone angle (θ) and Sauter Mean Diameter (SMD). Experimental results indicate that, within the operating conditions of this study, sliding arc plasma can significantly improve spray atomization characteristics. As Uin increases, Uout and discharge intensity increase, the spray cone angle increases by approximately 4–7° overall, and the SMD decreases by up to approximately 31.56%. As qair increases, both θ and SMD exhibit non-monotonic variation characteristics, with optimal atomization performance observed around 30 L/min. Under cross-flow conditions, aerodynamic shearing interacts synergistically with the electrodynamic and thermal effects of the plasma. This interaction further enhances droplet fragmentation and dispersion. Experimental results show that the spray cone angle can increase by up to approximately 15°. As the injection pressure difference increases, the inertia of the liquid jet increases, causing a delay in primary fragmentation and resulting in an upward trend in the SMD. However, by introducing additional perturbations and enhancing interfacial instability, the plasma still exhibits a more significant atomization enhancement effect under high-pressure conditions. Furthermore, the effective power consumption of the plasma excitation system in this experiment is approximately 22 W, accounting for an extremely low proportion of the total power of the engine system. Considering both the atomization improvement and the energy consumption level, this method achieves significant atomization enhancement with relatively low energy input, demonstrating good potential for engineering applications.
The breakdown voltage of argon, nitrogen, and their mixtures (25, 50, 75, and 90 vol% argon) was measured at 25, 70, and 110 degrees C (+/- 2 degrees C) and pressures from 101.3 to 2600 kPa. These conditions are relevant to industrial gasphase polyethylene reactors, where the use of argon for mitigating triboelectrification is under investigation. Measurements were conducted using parallel-plate electrodes with a gap between 0.996 and 1.065 mm housed in a heated high-pressure chamber. For pure gases, dielectric strength increased nonlinearly with pressure. Temperature effects were modest between 25 and 110 degrees C, with argon exhibiting a larger relative decline. Mixtures exhibited nonlinear behavior, with argon additions as small as 25 vol% causing a similar to 40% reduction in dielectric strength.
To address the challenge of intelligently predicting insulation strength for valve hall fitting-to-ground air gaps at high altitudes, this study proposes a prediction model based on the random forest (RF) algorithm. A total of 22 features comprising four atmospheric parameters and 18 electric field (EF) features are used as inputs. The model is trained on experimental data from 44 rod-plane and sphere-plane gaps at altitudes of 0 m, 55 m, 1100 m, and 2100 m. It successfully predicts the discharge voltages of 87 cap-to-ground and grading ring-to-ground gaps at altitudes of 1800 m, 2100 m, and 2400 m, achieving a mean absolute percentage error (MAPE) of 3.93%. These results verify the effectiveness and generalization performance of the proposed method. This study provides a reference for the insulation strength calculation of complex engineering air gaps at high altitudes.
One of the novel contributions of this study on the electroculture of Arabidopsis thaliana plant during its adult stage in a semi-hydroponic medium is the implementation of galvanostatic control to determine the two low magnitudes of the imposed electric field (0.1 and 0.2 V/cm), which were selected from the Ohmic region established by an interval of current potential values that fits the linear model. Under these conditions, the electrochemical cell used behaves as an electrical resistance, which ensures that the ionic species present in the medium move towards the root zone due to electromigration. This prevented the manifestation of undesirable effects in the granular substrate used as a culture medium, such as temperature increase, substrate dehydration, accelerated Faradaic reactions and drastic pH changes, which are related to speciation and nutrient availability. This study revealed that the effects of intermittent electrical stimulation (applied every 3 days) from the seedling to the adult stage of A. thaliana provoked an enhancement of growth and positive physiological responses, such as, the increase of chlorophyll and nutrient content in adult plants. In an independent experiment, it was verified that the electrical stimuli not only influenced the accumulation of auxins in the roots of Arabidopsis marker line seedlings (DR5:uidA), but also their transport to higher organs of the plant, favoring their development and growth. Therefore, it was confirmed that these results were solely due to the electric field influence.
Electrically assisted thermal management of dielectric liquids relies on a precise understanding of how applied electric fields interact with buoyancy-driven convection. This work presents a numerical investigation of electro-thermo-hydrodynamic (ETHD) convection in weakly conducting dielectric liquids subjected to a DC electric field and a destabilizing vertical temperature gradient between parallel-plate electrodes. The flow operates in the conduction regime of electrohydrodynamics (EHD), where free ions arise from reversible dissociation of neutral molecules-a process critically enhanced by the applied field through the Onsager (second Wien) effect. A central novelty of this study is the fully coupled and thermally consistent treatment of temperature-dependent material properties: ionic mobilities are distinguished for cations and anions and allowed to vary with temperature, as are liquid permittivity, viscosity, and density. This departs from the common simplifying assumption of identical, temperature-independent mobilities adopted in most prior conduction-regime studies. Dielectric body forces arising from permittivity gradients are retained alongside Coulomb forces and their influence is systematically assessed. The governing system-incompressible Navier-Stokes equations under the Boussinesq approximation, the heat equation, drift-diffusion-advection ion transport with dissociation-recombination source terms, and Gauss's law-is solved with a second-order finite-volume method. Parametric studies at Ra = 5000, electric Reynolds number Rel = 2, and conduction number C-0 = 6.5 reveal two distinct dynamical regimes as the temperature-sensitivity parameters L and N are varied, with the purely thermal Rayleigh-B & eacute;nard reference (no electric field) yielding a steady-state Nusselt number Nu_RB = 0.5105. When L = N <= 1 & times; 10(-5), the system settles into a stationary thermoconvective state with Nusselt numbers close to Nu_RB (Nu = 0.4809 for L = N = 0 and Nu = 0.4888 for L = N = 1 & times; 10(-5)), indicating that weak temperature sensitivity produces negligible modification of the purely thermal response. When L = N >= 1 & times; 10(-4) with Onsager number O = 200, the system enters a sustained limit-cycle oscillatory (overstable) regime in which the maximum velocity exhibits persistent oscillations that do not decay. The time-averaged Nusselt numbers are Nu = 0.3713 for L = N = 1 & times; 10(-4) and Nu = 0.4231 for L = N = 2 & times; 10(-4), both below Nu_RB, demonstrating that the oscillatory ETHD forcing reduces the net heat flux relative to purely thermal convection (-27% and -17% respectively). These results demonstrate that the interplay between field-enhanced dissociation, temperature-dependent permittivity, and mobility asymmetry governs both the stability threshold and the heat-transfer efficiency of ETHD conduction, and that a thermally consistent formulation is indispensable for quantitative prediction. The findings provide actionable design guidelines: operating with fluids of weak temperature sensitivity (L, N << 1 & times; 10(-4)) produces stationary convection close to the purely thermal RB response, while strong temperature sensitivity (L, N greater than or similar to 1 & times; 10(-4)) combined with high O triggers sustained oscillatory convection with a reduced time-averaged heat flux (-27% to -17% relative to Nu_RB depending on the sensitivity level).
The electrocoalescence of water droplets in oil is essential for emulsion separation, but the presence of an initial net charge on droplets can significantly alter interaction outcomes. This study numerically investigates the effect of droplet charge on the pairwise interaction of conducting droplets suspended in a dielectric liquid under a DC electric field. Using an arbitrary Lagrangian–Eulerian method with a moving mesh, the model resolves the full droplet dynamics, including approach, bridge formation, and subsequent coalescence or breakup. The simulations cover a range of electric field strengths and charge magnitudes (opposite sign, equal magnitude). Results show that increasing droplet charge raises the threshold field strength for coalescence up to 20%, which is favorable for purification. However, above this threshold, charged droplets undergo severe defragmentation instead of simple rebound, producing numerous small droplets that are detrimental to purification efficiency. The outcome is governed by the competition, after droplet contact, between bridge growth and structure stretching. Both of these processes, in turn, depend strongly on the kinetic energy of the droplets and, in particular, of their facing poles prior to collision. Initial inter-droplet distance is also critical: insufficient distance can prevent acceleration of charged droplets and trigger non-coalescence even at favorable field strengths. These findings indicate that uncontrolled droplet charge is undesirable in electrostatic demulsification, and it has to be accounted for when designing electrostatic oil cleaners.
Particles acting as contamination pose challenges in applications ranging from high-tech equipment to high-voltage switchgear. Although analytical models describe the motion of charged, conducting spherical particles well, they become inaccurate in the limiting case of two planar electrodes being closely spaced. The aim of this work is to quantify the deviation between analytical predictions and experimental observations in this regime. Through a combination of experiments and numerical simulations, the lift-off dynamics of a conducting solid sphere subjected to electric fields exceeding 1MV/m were investigated in an electrode gap comparable to the sphere diameter (1mm). From the lift-off acceleration measured using high-speed imaging, the electric force acting on the sphere was quantified and found to be in good agreement with numerical simulations and the analytical model of a single electrode and a single sphere by Felici (1966) when the sphere-to-gap ratio R/d was small. However, for a sphere approaching the size of the gap, the analytical model values were up to 20% lower than the experimental and numerical results, implying that the attractive electrostatic interactions between the sphere and the top electrode should be included in the analytical model in that limit case.
Highly efficient fabrication methods are urgently needed for high-performance materials that have a difficult environmental track record but cannot yet be replaced, such as fluoropolymers. Here we study the formation of hydrophobic nanocoatings by electrospraying PTFE nanopowder suspensions without additives, followed by thermal sintering. The spray expands electrostatically gradually, resulting in uniform crystalline sintered films, both on silicon and stainless steel. Besides characterizing the films’ morphology and crystallinity versus process parameters (by FIB-FESEM and XRD), we have found superior performance for PTFE-coated stainless-steel capillaries when used as electrospraying emitters with polymer solutions of low surface tension solvents.
For an open conducting cylinder in an axial external field, we calculate the resultant potential and field at all points, and also the longitudinal polarizability. The surface charge densities (interior and exterior) are also calculated. The results are exact in principle, but numerical evaluation requires the inversion of a matrix of known elements. Provided the cylinder is not much longer than its width, 3×3 matrices are sufficient. When the cylinder length increases to be greater than its diameter, the internal charge density decreases, and there is increasing amplification of the electric field on the axis, just outside the cylinder.
Human motion monitoring is crucial for wearable healthcare, sports analysis, and rehabilitation. Here, an In2Se3-based triboelectric nanogenerator (I-TENG) is developed for biomechanical energy harvesting and self-powered sensing. Built by layer-by-layer assembly using Kapton, Cu, PTFE, and compacted In2Se3 powders, the device delivers 700 V, 32 mu A, 200 nC, and 388 mu W, and durable operation, while maintaining stable responses under varied frequencies, forces, distances, temperatures, and humidity. It further generates distinguishable signals for finger, wrist, and elbow bending, as well as walking, running, and jumping, demonstrating wearable motion-monitoring potential.
Polymers have been widely applied in flexible sensors, electronic components and vibration energy harvesters, but their inherently low flexoelectric coefficients have become the critical bottleneck restricting their practical applications. In this work, PDMS electrets with controlled pre-strain (epsilon(p)) and thickness (h) were fabricated, and their impact polarization characteristics were systematically investigated via drop hammer impact tests and numerical simulations. The results demonstrate that the surface potential decay rate of the electret back surface (-s) is slower than that of the front surface (+s), and the decay rate increases with decreasing h. Notably, pre-strained and subsequently rebounded specimens exhibit the optimal surface potential retention capability. During impact loading, the stress of PDMS electrets is mainly concentrated in the central region, while the edge region experiences higher stress during the rebound phase. The impact polarization voltages of PDMS electrets range from 120 to 300 mV, which are about 4 similar to 10 times higher than those of PDMS (30 similar to 45 mV). In particular, the PDMS electret subjected to 50% pre-strain followed by rebound achieves a maximum polarization voltage of 618.11 mV. The equivalent flexoelectric coefficients of PDMS electrets reach approximately 10(-8) C m(-1), which is one order of magnitude higher than that of PDMS. This work provides critical insights for the development of high-performance functional polymers with superior electromechanical coupling properties.
