Corona Charging Research Articles

High‐Brightness and High‐Resolution Triboelectrification‐Induced Electroluminescence Skin for Photonic Imaging and Information Interaction

AbstractSelf‐powered visualized sensor with skin‐like functionality is highly anticipated for practical application in health monitoring, human‐machine interaction, and robotics. However, the existing methods are disadvantaged by their poor performance in sensitivity and spatial fidelity due to the low pixel density, brightness, or conformability. Herein, a novel self‐powered skin‐inspired visualized sensor (SP‐SIVS) is developed by means of triboelectrification‐induced electroluminescence (TIEL) technique. By integrating surface and bulk charge generation with a high‐voltage corona charging treatment, a significant improvement is achieved in the brightness (by 10‐fold) and spatial resolution (100 µm) of the SP‐SIVS. Meanwhile, Young's modulus (94 kPa) is maintained at a level comparable to human skin, with tensile strength and elongation exceeding 1000 kPa and 1000%, respectively. Furthermore, SP‐SIVS is verified as applicable to serve such purposes as wearable motion detection, fingerprint morphology imaging, and information interaction. This work contributes an innovative framework to the development of SP‐SIVS with high‐brightness, high‐resolution, and sustainability, laying a foundation for its popularization as a novel interactive medium required for advanced photonic applications.

Charging properties of atactic poly(styrene) microfibre mats charged with electrospinning and corona charging

Charging properties of atactic poly(styrene) microfibre mats charged with electrospinning and corona charging

Electrical Cleaning of Rough Spherical and Bumpy Abrasive Particles Charged by Corona Ions in Post-CMP

This study describes electrostatic methods for effective post-CMP (Chemical Mechanical Polishing) cleaning of contaminated wafers with rough spherical and bumpy abrasive particles. The case when corona ions charged the particles was studied. The extended JKR adhesion model for rough surfaces was used in the analysis. Charges were uniformly distributed across the entire particle surface for the corona charging. Removal of charged rough spherical and bumpy particles was investigated. The electric fields necessary to detach alumina particles with different numbers of bumps, contact asperities, and charges from wafer surfaces with varying roughness levels were evaluated. The present model predictions were compared against experimental data for the detaching polystyrene latex particles from an aluminum oxide substrate. It was shown that the model predictions for the electric detachment fields agree with the corresponding experimental data for the selected range of parameters. The model provides an approach for removing rough spherical and bumpy particles charged by corona ions in diverse applications, including post-CMP cleaning.

Investigation of Upward Leader Development Characteristics by Two Kinds of Charge Density Models in Wind Turbines

ABSTRACTThe upward discharge is a significant factor threatening the operation of wind farms. This paper investigates the inception and development of upward leaders of wind turbines' tip, where blade rotation prevents charge accumulation, using charge density models from laboratory discharges and artificially triggered lightning. The results indicate that larger return stroke currents create higher spatial potentials, and slower downward leader speeds allow for longer development time, favoring the development of upward leaders. As wind turbine sizes increase, the rotation of the blade tips resembles artificially triggered lightning, and the long air gap discharge model may underestimate the development of upward leaders. Calculations from the artificially triggered lightning model reveal improved upward leader formation when further laterally away from the downward leader within a certain distance, elucidating why multiple upward leaders are frequently observed around turbines. The striking distance and attractive radius are largely determined by the development of upward leaders. The absence of corona charge shielding at blade tips means upward leader inception is independent of downward leader velocity, emphasizing downward leaders' significant influence on turbines. Thus, the formula for estimating a wind turbine's lightning incidence requires integrating the return stroke current and velocity of the downward leader.

Investigation into negative corona discharge in steam jets and distribution characteristics of charged steam jets

Electricity provides a wide range of benefits for plant growth, and the electric field created by a charged steam jet exhibits significant potential for application in this field. This study investigates the electrical characteristics of charged steam jets, including the corona-discharge process, distribution of electric fields, and deposition currents. By installing a needle-ring electrode near the steam-jet exit, high-potential charged steam is generated within a confined space through the corona charging of droplets in the steam. The humid environment inside the steam jet considerably reduces the corona current compared with that of air. The outlet current is identified as a critical factor for assessing the charged steam-jet behaviour, with a higher outlet current indicating a stronger electric field and deposition current. The configuration of the electrode and the steam operational conditions, particularly the latter, affect the outlet current. Experimental results highlight the different electrical distribution characteristics of wet and saturated steam jets. Notably, the distributions of electric field and deposition currents, along with the depositional droplets and absolute-humidity increments exhibit asymmetry above and below the steam jet. This paper presents a discussion on the formation, development, and dissipative processes of charged droplets and an analysis into their possible movement trajectories under various forces. Generally, the asymmetric distribution of charged steam jets is caused by the asymmetric distribution of charged droplets or water-cluster molecules, which becomes more pronounced as one departs further from the steam-jet exit.

Overcoming Moisture‐Induced Charge Decay in Tribo‐Materials

AbstractThe paper extensively explores moisture‐induced charge decay in tribo‐materials, addressing charge generation fundamentals and overcoming strategies. Triboelectric effect and contact electrification models are discussed, with corona charging and hydro‐charging as effective charge generation methods. Moisture‐induced adverse effects, such as swelling and charge dissipation, are outlined. Electronegativity and dangling bonds' roles in charge traps are explored, along with the impact of functionalities on materials. Various strategies, including hydrophobic surfaces, crystalline phases, and water‐reactive materials, are proposed to counter moisture effects. Tribo‐materials are currently applied in energy, sensors, environment, and healthcare, with potential in smart skin sensors and implantable devices. Overcoming challenges, including high charge density and durability, can lead to breakthroughs, expanding applications to harsh environments like underwater and high temperatures.

Investigation on the Long-Term Stability of AlOx/SiNy:H and SiNy:H Passivation Layers During Illuminated Annealing at Elevated Temperatures

Most crystalline Si based solar cells, e.g. passivated emitter and rear cells, rely on SiNy:H and AlOx/SiNy:H passivation layers. In this work, the long-term behavior of minority charge carrier lifetime in such symmetrically passivated samples during illuminated annealing at elevated temperatures is investigated by means of photoconductance decay based lifetime measurements, corona charging and capacitance voltage measurements. Thereby, AlOx layers, which are known to reduce H in-diffusion due to their barrier properties, deposited by atmospheric pressure chemical vapor deposition as well as by atomic layer deposition were considered enabling a comparison of different deposition techniques. The frequently published behavior of the bulk related degradation could be confirmed and the qualitative correlation between maximum defect density and the changing total amount of H in the Si bulk due to the barrier properties of the individual layers dielectric layers could be shown. Furthermore, for the subsequently observed degradation accelerated by a treatment at higher temperatures, literature indicates degradation to be caused by surface related degradation. Investigations on field effect passivation during degradation by means of corona charging and CV measurements showed a large drop in fixed negative charges in the passivation layer stacks.

Electrical detachment of bumpy particles and rough spherical particles charged by corona ions

ABSTRACT Electrostatic detachment of bumpy and spherical particles with rough surfaces charged by corona ions was studied. Corona charging leads to uniformly distributed charges across the entire particle surface. The JKR adhesion model and electrostatic interactions of these particles in contact with a surface were evaluated. The electrostatic forces for particles carrying fixed charges per unit mass were evaluated. The study investigated the electric fields required to detach charged particles from rough surfaces for different charge levels, various numbers of bumps for bumpy particles, and different numbers of contact asperities for rough spherical particles. The accuracy of the model predictions for detaching charged particles from substrates with varying degrees of roughness was assessed by comparison with the experimental data, which indicated that the predicted electric detachment fields agreed with the experimental data for the selected range of parameters. The proposed model provides a helpful framework for removing bumpy particles, and rough spherical particles charged by corona ions in various applications. For 8.3 μm polystyrene charged latex particles, approximately 46% and 62% reductions in detachment electric field were found for a 10% decrease in the roughness parameter for bumpy particles and rough spheres, respectively.

Electret Modulation Strategy to Enhance the Photosensitivity Performance of Two-Dimensional Molybdenum Sulfide.

Due to the limited light absorption efficiency of atomic thickness layers and the existence of quenching effects, photodetectors solely made of transition metal dichalcogenides (TMDs) have exhibited an unsatisfactory detection performance. In this article, electret/TMD hybridized devices were proposed by vertically coupling a MoS2 channel and the PTFE film, which reveals an optimized photodetection behavior. Negative charges were generated in the PTFE layer through the corona charging method, akin to applying a negative bias on the MoS2 channel in lieu of a traditional voltage-driven back gate. Under a charging voltage of -6 kV, PTFE/MoS2 devices reveal improved photodetection performance (Rhybrid = 67.95A/W versus Ronly = 3.37 A/W, at 470 nm, 1.20 mW cm-2) and faster recovery speed (τd(hybrid) = 2000 ms versus τd(only) = 2900 ms) compared to those bare MoS2 counterparts. The optimal detection performance (2 orders of magnitude) was obtained when the charging voltage was -2 kV, limited by the minimum of the carrier density in MoS2 channels. This study provides an alternative strategy to optimize optoelectronic devices based on the 2D components through non-voltage-driven gating.

Combined effect of heat and corona charge on molecular delivery to a T cell line in vitro.

With the rapid increase of gene and immunotherapies for treating cancer, there is a need to efficiently transfect cells. Previous studies suggest that electrotransfer can provide a non-viral method for gene delivery. Electrotransfer traditionally relies upon the application of direct current pulses to the cells of interest. Corona charge was investigated in this study as an alternative to traditional methods as a means of creating the electric field necessary to deliver materials via electrotransfer. The goal was to determine if there was an increase in molecular delivery across the membrane of a human T cell line used as a model system. In a novel dish created for the study, the effects of elevated temperatures (37, 40, 43, and 45°C) during the treatment process were also examined in combination with corona charge application. Results showed that treating cells with corona charge at room temperature (~23°C) caused a statistically significant increase in molecular delivery while maintaining viability. Heat alone did not cause a statistically significant effect on molecular delivery. Combined corona charge treatment and heating resulted in a statistically significant increase on molecular delivery compared to controls that were only heated. Combined corona charge treatment and heating to all temperatures when compared to controls treated at room temperature, showed a statistically significant increase in molecular delivery.

Bicomponent spunbond filters doped with polytetrafluoroethylene nanoparticles for long-term efficient fine particle removal

Electret fiber-based air filtration materials find extensive applications in various fields, including particulate matter filtration, indoor purification, and epidemic prevention. However, achieving high-efficiency filtration with low resistance and long-term stability remains a challenge. In this study, we present a novel approach to fabricate sheath-core bicomponent spunbond filters (BCSFs) doped with polytetrafluoroethylene nanoparticles (PNPs) using bicomponent spunbond, through-air bonding, and corona charging techniques. This strategy enables the filtration material to possess low air resistance, long-term stable filtration efficiency, and a high dust holding capacity. The resulting BCSFs-PNPs exhibit remarkable filtration performance, with a filtration efficiency of 99.25% and a dust holding capacity of up to 11.48 g m−2, while maintaining a pressure drop as low as 37.87 Pa. Notably, the filtration efficiency of BCSFs-PNPs only experienced a slight decrease of 3.58% over a period of 180 days, demonstrating excellent long-term stability. The successful preparation of BCSFs-PNPs using corona charging technology holds great promise and offers valuable insight for the design and application of advanced air filtration materials.

Direct Current Corona Characteristics of Innovative Portable High Voltage dc to dc Booster Device in Corona Charging Setup

In the present work an experimental investigation has been carried out to study the corona characteristics of a portable high voltage dc to dc booster device proposed and used by us for the first time as an innovation in corona charging of electrets. The experiments were conducted in a point-to-plane system to measure the corona current I as a function of applied corona voltage V and inter-electrode separation. Obtained results have been analyzed and discussed successfully in the light of cited works and show that both positive and negative corona produced by this device is consistent with the Townsend Relation adapted for point-to-plane geometry. This device is suitable and effective in applications where the local corona is required.

Experimental study on DC corona charging characteristics of powder particles with different properties

In this paper, the charging characteristics of powder particles with different properties under DC discharge corona conditions were studied experimentally. The influence of different charging voltages and different charging structures on the charge-mass ratio of particles was analyzed through ELPI measurement. The experimental results show that the far-field charging structure of the electrode can effectively charge powder materials like Graphite micro powder, copper sulfide, talcum powder, and porous material (Si Al) within the particle size range of 0.1 μm−10 μm; When there is no streamer or spark between the charging electrode and the grounding electrode of the charging device, the higher the charging voltage is, the higher the degree of air ionization is, and the better the charging effect on particles is; Under the same charge condition, the charge-mass ratio of particles decreases with the increase of particle size.

Change of electrostatic field polarity in the melt-blown polypropylene electret fabrics with corona charging

Corona-charged melt-blown polypropylene (MBPP) electret fabrics are promising candidates for air filtration, wearable sensing and energy harvesting applications. However, the underlying corona charging mechanism still needs further exploration to enhance the charge storage performance of electret fabrics. Herein, the phenomenon of surface electrostatic field polarity change in corona-charged MBPP electret fabrics is reported. By using negative corona charging and altering charging conditions such as sample size, charging time, charging voltage, discharge electrode shape and ground electrode contacting sample mode, three electrostatic field distribution modes can be formed on the two sides of samples, including (i) both front and back sides are negative; (ii) the front side is negative, and the back is positive; (iii) the front side is positive, and the back is negative. A corona charging mechanism based on plasma sheath is proposed as an explanation. The origin location and thickness of plasma sheath, which are affected by charging conditions, determine the electrostatic field polarity of MBPP fabrics. MBPP electrets with different electrostatic field polarities do not differ substantially in charge storage stability.

Synchronized 3D Printing and Corona Charging for One-Step Prototyping of Polarized Polylactic Acid Electrets.

Three-dimensional (3D) printing technology is advantageous in the fast prototyping of complex structures, but its utilization in functional material fabrication is still limited due to a lack of activation capability. To fabricate and activate the functional material of electrets, a synchronized 3D printing and corona charging method is presented to prototype and polarize polylactic acid electrets in one step. By upgrading the 3D printer nozzle and incorporating a needle electrode to apply high voltage, parameters such as needle tip distance and applied voltage level were compared and optimized. Under different experimental conditions, the average surface distribution in the center of the samples was -1498.87 V, -1115.73 V, and -814.51 V. Scanning electron microscopy results showed that the electric field contributes to keeping the printed fiber structure straight. The polylactic acid electrets exhibited relatively uniform surface potential distribution on a sufficiently large sample surface. In addition, the average surface potential retention rate was improved by 12.021-fold compared to ordinary corona-charged samples. The above advantages are unique to the 3D-printed and polarized polylactic acid electrets, proving that the proposed method is suitable for quickly prototyping and effectively polarizing the polylactic acid electrets simultaneously.

Optimizing Non-Contact Doping and Electrical Defect Metrology for Production of SiC Epitaxial Wafers

The recently introduced corona charge non-contact capacitance-voltage technique, CnCV, is analyzed considering the production needs of epitaxial SiC wafers. The interfering mechanism of charge dissipation on fresh epitaxial 4H-SiC is identified as surface diffusion and is effectively eliminated by optimized ultraviolet pretreatment (UVPT). It is shown that optimized UVPT increases the CnCV dopant measurement voltage range and the depth of profiling. Concurrent UVPT and measurement provides a practical solution for improving throughput for multiple wafers. Electrical defect mapping shows that UVPT reduces the effective defect size. This will be helpful to avoid defects in patterns used for CnCV dopant measurements.

Three-Dimensional Simulation of Corona Discharge in a Double-Needle System during a Thunderstorm

The effect of corona discharge from buildings or structures on the surrounding atmospheric electric field is very important in the measurement of urban atmospheric electric fields and the early warning of lightning. However, most previous studies were focused on independent buildings, with little research on three-dimensional building groups. Therefore, based on three-dimensional numerical simulation technology, this paper uses a double-needle system to simulate the characteristics of thunderstorm corona discharge from two equal-height buildings separated by a variable distance. The shielding effect of the double-needle system on the ground electric field is evaluated both with and without corona discharge, and the main conclusions are as follows: (1) The larger the distance between the two needles, the closer the peak corona current from each tip of the double-needle system is to that from an independent lightning rod at the same height. When the peak corona current from each tip of the double-needle system equals the peak corona current from an independent lightning rod at the same height to some level of approximation, the distance between the two needle systems is determined by the needle height at this time. (2) If the distance between the two needles is 0.1 m, the corona charge released by the double-needle system is almost equal to that released by an independent lightning rod. The corona charge released by the double-needle system is approximately twice as much as that released by an independent lightning rod when the distance between the two needles is increased to a certain value that increases with the needle height and the time of corona discharge. (3) The greater the value of the time of corona discharge, the stronger the shielding effect of the corona discharge on the ground electric field and the larger the shielding range, but the greater the value of the needle height, the smaller the shielding range. (4) Compared with the shielding effect with no corona discharge, that with corona discharge is greater, but the greater the value of the needle height, the less the enhancement. For example, for corona discharge with a time of 10 s, the needle height is 20 m, and the shielding range is ca. 70 m, which is 8.8 times that without corona discharge; however, for the needle height of 100 m, the shielding range is ca. 150 m, which is only 1.5 times that without corona discharge.

Fabrication of Laminated Micro/Nano Filter and Its Application for Inhalable PM Removal

Particulate matter (PM) with a diameter of 0.3 µm is inhalable and brings great threats to human health. Traditional meltblown nonwovens used for air filtration need to be treated by high voltage corona charging, which has the problem of electrostatic dissipation and thus reduces the filtration efficiency. In this work, a kind of composite air-filter with high efficiency and low resistance was fabricated by alternating lamination of ultrathin electronspun nano-layer and melt-blown layer without corona charging treatment. The effects of fiber diameter, pore size, porosity, layer number, and weight on filtration performance were investigated. Meanwhile, the surface hydrophobicity, loading capacity, and storage stability of the composite filter were studied. The results indicate that the filters (18.5 gsm) laminated by 10 layers fiber-webs present excellent filtration efficiency (97.94%), low pressure drop (53.2 Pa), high quality factor (QF 0.073 Pa-1), and high dust holding capacity (9.72 g/m2) for NaCl aerosol particles. Increasing the layers and reducing individual layer weight can significantly improve filtration efficiency and reduce pressure drop of the filter. The filtration efficiency decayed slightly from 97.94% to 96.48% after 80 days storage. The alternate arrangement of ultra-thin nano and melt-blown layers constructed a layer-by-layer interception and collaborative filtering effect in the composite filter, realizing the high filtration efficiency and low resistance without high voltage corona charging. These results provided new insights for the application of nonwoven fabrics in air filtration.

Bioactivity Enhancement of Plasma-Sprayed Hydroxyapatite Coatings through Non-Contact Corona Electrical Charging.

Atmospheric plasma spray (APS) remains the only certified industrial process to produce hydroxyapatite (Hap) coatings on orthopaedic and dental implants intended for commercialization. Despite the established clinical success of Hap-coated implants, such as hip and knee arthroplasties, a concern is being raised regarding the failure and revision rates in younger patients, which are increasing rapidly worldwide. The lifetime risk of replacement for patients in the 50-60 age interval is about 35%, which is significantly higher than 5% for patients aged 70 or older. Improved implants targeted at younger patients are a necessity that experts have been alerted to. One approach is to enhance their bioactivity. For this purpose, the method with the most outstanding biological results is the electrical polarization of Hap, which remarkably accelerates implant osteointegration. There is, however, the technical challenge of charging the coatings. Although this is straightforward on bulk samples with planar faces, it is not easy on coatings, and there are several problems regarding the application of electrodes. To the best of our knowledge, this study demonstrates, for the first time, the electrical charging of APS Hap coatings using a non-contact, electrode-free method: corona charging. Bioactivity enhancement is observed, establishing the promising potential of corona charging in orthopedics and dental implantology. It is found that the coatings can store charge at the surface and bulk levels up to high surface potentials (>1000 V). The biological in vitro results show higher Ca2+ and P5+ intakes in charged coatings compared to non-charged coatings. Moreover, a higher osteoblastic cellular proliferation is promoted in the charged coatings, indicating the promising potential of corona-charged coatings when applied in orthopedics and dental implantology.

Stable chemical enhancement of passivating nanolayer structures grown by atomic layer deposition on silicon.

Incorporation of carrier-selective passivating contacts is on the critical path for approaching the theoretical power conversion efficiency limit in silicon solar cells. We have used plasma-enhanced atomic layer deposition (ALD) to create ultra-thin films at the single nanometre-scale which can be subsequently chemically enhanced to have properties suitable for high-performance contacts. Negatively charged 1 nm thick HfO2 films exhibit very promising passivation properties - exceeding those of SiO2 and Al2O3 at an equivalent thickness - providing a surface recombination velocity (SRV) of 19 cm s-1 on n-type silicon. Applying an Al2O3 capping layer to form Si/HfO2/Al2O3 stacks gives additional passivation, resulting in an SRV of 3.5 cm s-1. Passivation quality can be further improved via simple immersion in hydrofluoric acid, which results in SRVs < 2 cm s-1 that are stable over time (tested for ∼50 days). Based on corona charging analysis, Kelvin probe measurements and X-ray photoelectron spectroscopy, the chemically induced enhancement is consistent with changes at the dielectric surface and not the Si/dielectric interface, with fluorination of the Al2O3 and underlying HfO2 films occurring after just 5 s HF immersion. Our results show that passivation is enhanced when the oxides are fluorinated. The Al2O3 top layer of the stack can be thinned down by etching, offering a new route for fabrication of ultra-thin highly passivating HfO2-containing nanoscale thin films.